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All questions of Time Varying Electromagnetic Fields for Electronics and Communication Engineering (ECE) Exam
Find the time constant of a capacitor with capacitance of 2 microfarad having an internal resistance of 4 megaohm.- a)2
- b)0.5
- c)8
- d)0.25
Correct answer is option 'C'. Can you explain this answer?
Find the time constant of a capacitor with capacitance of 2 microfarad having an internal resistance of 4 megaohm.
a)
2
b)
0.5
c)
8
d)
0.25
|
Sanvi Kapoor answered |
Answer: c
Explanation: The time constant of capacitor is given by T = RC, where R = 4×106 and C = 2×10-6. Thus T = 4×106 x2x10-6 = 8 seconds.
Explanation: The time constant of capacitor is given by T = RC, where R = 4×106 and C = 2×10-6. Thus T = 4×106 x2x10-6 = 8 seconds.
For a perfect dielectric, which parameter will be zero?- a)Conductivity
- b)Frequency
- c)Permittivity
- d)Permeability
Correct answer is option 'A'. Can you explain this answer?
For a perfect dielectric, which parameter will be zero?
a)
Conductivity
b)
Frequency
c)
Permittivity
d)
Permeability
|
|
Sanvi Kapoor answered |
Answer: a
Explanation: The conductivity will be minimum for a dielectric. For a perfect dielectric, the conductivity will be zero.
Explanation: The conductivity will be minimum for a dielectric. For a perfect dielectric, the conductivity will be zero.
The conductivity in free space medium is- a)Infinity
- b)Unity
- c)Zero
- d)Negative
Correct answer is option 'C'. Can you explain this answer?
The conductivity in free space medium is
a)
Infinity
b)
Unity
c)
Zero
d)
Negative
|
Yash Patel answered |
Answer: c
Explanation: As the charge carriers are not available in free space, the conductivity will be very low. For ideal cases, the conductivity can be taken as zero.
Explanation: As the charge carriers are not available in free space, the conductivity will be very low. For ideal cases, the conductivity can be taken as zero.
In free space, which parameter will be unity?- a)Permittivity
- b)Absolute permittivity
- c)Relative permittivity
- d)Permeability
Correct answer is option 'C'. Can you explain this answer?
In free space, which parameter will be unity?
a)
Permittivity
b)
Absolute permittivity
c)
Relative permittivity
d)
Permeability
|
Ravi Singh answered |
Answer: c
Explanation: The relative permittivity is a constant for a particular material. It is unity for free space or air. The absolute permittivity is a constant given by 8.854 x 10-12 C/m2.
Explanation: The relative permittivity is a constant for a particular material. It is unity for free space or air. The absolute permittivity is a constant given by 8.854 x 10-12 C/m2.
The Gauss law for magnetic field is valid in- a)Air
- b)Conductor
- c)Dielectric
- d)All cases
Correct answer is option 'D'. Can you explain this answer?
The Gauss law for magnetic field is valid in
a)
Air
b)
Conductor
c)
Dielectric
d)
All cases
|
|
Sanvi Kapoor answered |
Answer: d
Explanation: The Gauss law for magnetic field states that the divergence of B is always zero. This is valid for all cases like free space, dielectric medium etc.
Explanation: The Gauss law for magnetic field states that the divergence of B is always zero. This is valid for all cases like free space, dielectric medium etc.
Which components exist in an electromagnetic wave?- a)Only E
- b)Only H
- c)Both E and H
- d)Neither E or H
Correct answer is option 'C'. Can you explain this answer?
Which components exist in an electromagnetic wave?
a)
Only E
b)
Only H
c)
Both E and H
d)
Neither E or H
|
|
Sanvi Kapoor answered |
Answer: c
Explanation: In an electromagnetic wave, the electric and magnetic components coexist. They propagate perpendicular to each other and to the direction of propagation in space.
Explanation: In an electromagnetic wave, the electric and magnetic components coexist. They propagate perpendicular to each other and to the direction of propagation in space.
Choose the optical fibre material from the given materials.- a)Glass
- b)Plastic
- c)Silica
- d)Quartz
Correct answer is option 'C'. Can you explain this answer?
Choose the optical fibre material from the given materials.
a)
Glass
b)
Plastic
c)
Silica
d)
Quartz
|
Lavanya Menon answered |
Answer: c
Explanation: Silica is the most dominant optical fibre material. This is because of its hardness, flexibility, melting point. Also it is an easily available material.
Explanation: Silica is the most dominant optical fibre material. This is because of its hardness, flexibility, melting point. Also it is an easily available material.
The permeability of a dielectric material in air medium will be- a)Absolute permeability
- b)Relative permeability
- c)Product of absolute and relative permeability
- d)Unity
Correct answer is option 'A'. Can you explain this answer?
The permeability of a dielectric material in air medium will be
a)
Absolute permeability
b)
Relative permeability
c)
Product of absolute and relative permeability
d)
Unity
|
Zoya Sharma answered |
Answer: a
Explanation: The total permeability is the product of the absolute and the relative permeability. In air medium, the relative permeability will be unity. Thus the total permeability is equal to the absolute permeability given by 4π x 10-7 units.
Explanation: The total permeability is the product of the absolute and the relative permeability. In air medium, the relative permeability will be unity. Thus the total permeability is equal to the absolute permeability given by 4π x 10-7 units.
Identify the polarisation of the wave given, Ex = Exo cos wt and Ey = Eyo sin wt. The phase difference is +900.- a)Left hand circularly polarised
- b)Right hand circularly polarised
- c)Left hand elliptically polarised
- d)Right hand elliptically polarised
Correct answer is option 'C'. Can you explain this answer?
Identify the polarisation of the wave given, Ex = Exo cos wt and Ey = Eyo sin wt. The phase difference is +900.
a)
Left hand circularly polarised
b)
Right hand circularly polarised
c)
Left hand elliptically polarised
d)
Right hand elliptically polarised
|
Uday Saini answered |
Answer: c
Explanation: The magnitude of the Ex and Ey components are not same. Thus it is elliptical polarisation. For +90 phase difference, the polarisation is left handed. In other words, the rotation is in clockwise direction. Thus the polarisation is left hand elliptical.
Explanation: The magnitude of the Ex and Ey components are not same. Thus it is elliptical polarisation. For +90 phase difference, the polarisation is left handed. In other words, the rotation is in clockwise direction. Thus the polarisation is left hand elliptical.
Mutual inductance between two closely coupled coils is 2 H. Now, if the number of turns in one coil is reduced by 50 percent and those of the other coil is doubled then, new value of mutual inductance is:- a)2 H
- b)8 H
- c)1 H
- d)4 H
Correct answer is option 'A'. Can you explain this answer?
Mutual inductance between two closely coupled coils is 2 H. Now, if the number of turns in one coil is reduced by 50 percent and those of the other coil is doubled then, new value of mutual inductance is:
a)
2 H
b)
8 H
c)
1 H
d)
4 H
|
Pooja Patel answered |
Concept:
The inductance of a coil is given by,
The inductance of a coil is given by,
μ0 is magnetic permeability of free space
μr is relative permeability
N is number if turns
A is cross-sectional area
l is length
Calculation:
Given that M = 2 H
If the turns of one coil are decreased to half and the other is doubled.
Now the new value of the mutual inductance would be 2 H.
Two coupled coils have self inductances L1 = 10 mH and L2 = 20 mH.
The co-efficient of coupling (K) being 0.75 in the air. Voltage in the second coil when the current in circuit is given by I = 2 sin (314t) A is _______- a)3.14 cos (314t) V
- b)3.33 sin (314t) V
- c)6.66 cos (314t) V
- d)6.28 cos (314t) V
Correct answer is option 'C'. Can you explain this answer?
Two coupled coils have self inductances L1 = 10 mH and L2 = 20 mH.
The co-efficient of coupling (K) being 0.75 in the air. Voltage in the second coil when the current in circuit is given by I = 2 sin (314t) A is _______
The co-efficient of coupling (K) being 0.75 in the air. Voltage in the second coil when the current in circuit is given by I = 2 sin (314t) A is _______
a)
3.14 cos (314t) V
b)
3.33 sin (314t) V
c)
6.66 cos (314t) V
d)
6.28 cos (314t) V
|
Tharakesh Vini answered |
M=k√wl^2
m=0.75√200
=10.68
=0.1068 H
v2= m di/dt
=0.106 d/dt (2sin(314t)
6.66cos(314t) v
m=0.75√200
=10.68
=0.1068 H
v2= m di/dt
=0.106 d/dt (2sin(314t)
6.66cos(314t) v
In waveguides, which of the following conditions will be true?- a)V > c
- b)V < c
- c)V = c
- d)V >> c
Correct answer is option 'A'. Can you explain this answer?
In waveguides, which of the following conditions will be true?
a)
V > c
b)
V < c
c)
V = c
d)
V >> c
|
Mansi Choudhury answered |
Answer: a
Explanation: In waveguides, the phase velocity will always be greater than the speed of light. This enables the wave to propagate through the waveguide. Thus V > c is the required condition.
Explanation: In waveguides, the phase velocity will always be greater than the speed of light. This enables the wave to propagate through the waveguide. Thus V > c is the required condition.
The frequency in rad/sec of a wave with velocity of that of light and phase constant of 20 units is (in GHz)- a)6
- b)60
- c)600
- d)0.6
Correct answer is option 'A'. Can you explain this answer?
The frequency in rad/sec of a wave with velocity of that of light and phase constant of 20 units is (in GHz)
a)
6
b)
60
c)
600
d)
0.6
|
|
Sanvi Kapoor answered |
Answer: a
Explanation: The velocity of a wave is given by V = ω/β. To get ω, put v = 3 x 108 and β = 20. Thus ω = vβ = 3 x 108 x 20 = 60 x 108 = 6 GHz.
Explanation: The velocity of a wave is given by V = ω/β. To get ω, put v = 3 x 108 and β = 20. Thus ω = vβ = 3 x 108 x 20 = 60 x 108 = 6 GHz.
Calculate the emf of a material having flux density 5sin t in an area of 0.5 units.- a)2.5 sin t
- b)-2.5 cos t
- c)-5 sin t
- d)5 cos t
Correct answer is option 'D'. Can you explain this answer?
Calculate the emf of a material having flux density 5sin t in an area of 0.5 units.
a)
2.5 sin t
b)
-2.5 cos t
c)
-5 sin t
d)
5 cos t
|
Harsh Kulkarni answered |
Answer: d
Explanation: The emf can be written as Vemf = -d(∫B.ds)/dt. It can be written as Vemf = -B= -5sin t, since the integration and differentiation gets cancelled.
Explanation: The emf can be written as Vemf = -d(∫B.ds)/dt. It can be written as Vemf = -B= -5sin t, since the integration and differentiation gets cancelled.
A transformer has 350 primary turns and 1050 secondary turns. The primary winding is connected across a 230 V, 50 Hz supply. The induced EMF in the secondary will be- a)690 V, 50 Hz
- b)690 V, 150 Hz
- c)350 V, 150 Hz
- d)115 V, 50 Hz
Correct answer is option 'A'. Can you explain this answer?
A transformer has 350 primary turns and 1050 secondary turns. The primary winding is connected across a 230 V, 50 Hz supply. The induced EMF in the secondary will be
a)
690 V, 50 Hz
b)
690 V, 150 Hz
c)
350 V, 150 Hz
d)
115 V, 50 Hz
|
Kritika Gupta answered |
Transformer Basics
A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two or more coils of wire called windings, which are electrically insulated from each other but magnetically linked. The primary winding is connected to the input voltage source, while the secondary winding is connected to the load.
Transformer Turns Ratio
The turns ratio of a transformer is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. It is represented by the symbol "N" and is calculated as:
N = (Number of turns in primary winding) / (Number of turns in secondary winding)
In this case, the transformer has 350 primary turns and 1050 secondary turns. Therefore, the turns ratio can be calculated as:
N = 350 / 1050
N = 1 / 3
Induced EMF in the Secondary Winding
The induced electromotive force (EMF) in the secondary winding of a transformer can be calculated using the turns ratio and the applied voltage in the primary winding. The induced EMF is given by the equation:
EMF_secondary = Turns ratio * EMF_primary
In this case, the applied voltage in the primary winding is 230 V. Using the turns ratio calculated earlier (N = 1/3), we can calculate the induced EMF in the secondary winding as:
EMF_secondary = (1/3) * 230 V
EMF_secondary = 76.67 V
However, it is important to note that the induced EMF in the secondary winding is not affected by the frequency of the input voltage. Therefore, the induced EMF in the secondary winding will be:
EMF_secondary = 76.67 V, 50 Hz
Conclusion
The correct answer is option 'A' - the induced EMF in the secondary winding will be 690 V, 50 Hz. This is calculated using the turns ratio and the applied voltage in the primary winding. The frequency of the input voltage does not affect the induced EMF in the secondary winding.
A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two or more coils of wire called windings, which are electrically insulated from each other but magnetically linked. The primary winding is connected to the input voltage source, while the secondary winding is connected to the load.
Transformer Turns Ratio
The turns ratio of a transformer is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. It is represented by the symbol "N" and is calculated as:
N = (Number of turns in primary winding) / (Number of turns in secondary winding)
In this case, the transformer has 350 primary turns and 1050 secondary turns. Therefore, the turns ratio can be calculated as:
N = 350 / 1050
N = 1 / 3
Induced EMF in the Secondary Winding
The induced electromotive force (EMF) in the secondary winding of a transformer can be calculated using the turns ratio and the applied voltage in the primary winding. The induced EMF is given by the equation:
EMF_secondary = Turns ratio * EMF_primary
In this case, the applied voltage in the primary winding is 230 V. Using the turns ratio calculated earlier (N = 1/3), we can calculate the induced EMF in the secondary winding as:
EMF_secondary = (1/3) * 230 V
EMF_secondary = 76.67 V
However, it is important to note that the induced EMF in the secondary winding is not affected by the frequency of the input voltage. Therefore, the induced EMF in the secondary winding will be:
EMF_secondary = 76.67 V, 50 Hz
Conclusion
The correct answer is option 'A' - the induced EMF in the secondary winding will be 690 V, 50 Hz. This is calculated using the turns ratio and the applied voltage in the primary winding. The frequency of the input voltage does not affect the induced EMF in the secondary winding.
Identify the INCORRECT statement among the given options regarding mutual inductance.- a)Mutual inductance is a geometric quantity
- b)It is independent of the current in the circuit
- c)Counter wound coils help in increasing the mutual inductance
- d)Transformers have a large mutual inductance
Correct answer is option 'B'. Can you explain this answer?
Identify the INCORRECT statement among the given options regarding mutual inductance.
a)
Mutual inductance is a geometric quantity
b)
It is independent of the current in the circuit
c)
Counter wound coils help in increasing the mutual inductance
d)
Transformers have a large mutual inductance
|
Divya Nair answered |
Explanation:
Mutual inductance is a geometric quantity:
Mutual inductance is a geometric quantity that describes the relationship between two coils of wire. It depends on the number of turns in each coil, the relative orientation of the coils, and the permeability of the medium between the coils.
It is independent of the current in the circuit:
Mutual inductance is not independent of the current in the circuit. It is directly proportional to the current flowing through one coil and the rate of change of current in the other coil. Therefore, mutual inductance is influenced by the current in the circuit.
Counter wound coils help in increasing the mutual inductance:
Counter wound coils are coils wound in opposite directions. When two coils are wound in this manner, the magnetic field produced by one coil adds to the magnetic field produced by the other coil, resulting in an increase in mutual inductance between the coils.
Transformers have a large mutual inductance:
Transformers are devices that utilize mutual inductance to transfer electrical energy from one circuit to another. They consist of two or more coils of wire that are magnetically coupled, resulting in a large mutual inductance which enables efficient energy transfer between the coils.
Therefore, the incorrect statement among the given options is that mutual inductance is independent of the current in the circuit.
Mutual inductance is a geometric quantity:
Mutual inductance is a geometric quantity that describes the relationship between two coils of wire. It depends on the number of turns in each coil, the relative orientation of the coils, and the permeability of the medium between the coils.
It is independent of the current in the circuit:
Mutual inductance is not independent of the current in the circuit. It is directly proportional to the current flowing through one coil and the rate of change of current in the other coil. Therefore, mutual inductance is influenced by the current in the circuit.
Counter wound coils help in increasing the mutual inductance:
Counter wound coils are coils wound in opposite directions. When two coils are wound in this manner, the magnetic field produced by one coil adds to the magnetic field produced by the other coil, resulting in an increase in mutual inductance between the coils.
Transformers have a large mutual inductance:
Transformers are devices that utilize mutual inductance to transfer electrical energy from one circuit to another. They consist of two or more coils of wire that are magnetically coupled, resulting in a large mutual inductance which enables efficient energy transfer between the coils.
Therefore, the incorrect statement among the given options is that mutual inductance is independent of the current in the circuit.
In conductors, which two parameters are same?- a)Wavelength and phase constant
- b)Phase and attenuation constant
- c)Attenuation constant and skin depth
- d)Skin depth and wavelength
Correct answer is option 'B'. Can you explain this answer?
In conductors, which two parameters are same?
a)
Wavelength and phase constant
b)
Phase and attenuation constant
c)
Attenuation constant and skin depth
d)
Skin depth and wavelength
|
Sushant Mehta answered |
Answer: b
Explanation: In conductors, which are considered to be lossy, the attenuation and the phase constant are the same. It is given by α=β= √(ωμσ/2).
Explanation: In conductors, which are considered to be lossy, the attenuation and the phase constant are the same. It is given by α=β= √(ωμσ/2).
In free space, the charge carriers will be- a)0
- b)1
- c)100
- d)Infinity
Correct answer is option 'A'. Can you explain this answer?
In free space, the charge carriers will be
a)
0
b)
1
c)
100
d)
Infinity
|
Rounak Rane answered |
Answer: a
Explanation: Free space is not a conductor. Thus the charge carrier in free space is assumed to be zero. But the free space consists of particles or ions that get ionized during conduction.
Explanation: Free space is not a conductor. Thus the charge carrier in free space is assumed to be zero. But the free space consists of particles or ions that get ionized during conduction.
The Brewster angle is expressed as - a)Tan-1(n)
- b)Tan-1(n1/n2)
- c)Tan-1(n2/n1)
- d)Tan (n)
Correct answer is option 'C'. Can you explain this answer?
The Brewster angle is expressed as
a)
Tan-1(n)
b)
Tan-1(n1/n2)
c)
Tan-1(n2/n1)
d)
Tan (n)
|
|
Sushant Mehta answered |
Answer: c
Explanation: The tangent of the Brewster angle is the ratio of the refractive indices of the second medium to that of the first medium. It is given by tan θb= n2/n1. Thus the Brewster angle will be θb = tan-1(n2/n1).
Explanation: The tangent of the Brewster angle is the ratio of the refractive indices of the second medium to that of the first medium. It is given by tan θb= n2/n1. Thus the Brewster angle will be θb = tan-1(n2/n1).
In a coil current changes from 2A to 4A in 0.05 second. If the average induced e.m.f. is 8 volt, then coefficient of self inductance is:- a)0.2H
- b)0.1H
- c)0.8H
- d)0.4H
Correct answer is option 'A'. Can you explain this answer?
In a coil current changes from 2A to 4A in 0.05 second. If the average induced e.m.f. is 8 volt, then coefficient of self inductance is:
a)
0.2H
b)
0.1H
c)
0.8H
d)
0.4H
|
|
Pooja Patel answered |
Concept:
Self-Induction
- Whenever the electric current passing through a coil changes, the magnetic flux linked with it will also change.
- As a result of this, in accordance with Faraday’s laws of electromagnetic induction, an emf is induced in the coil which opposes the change that causes it.
- This phenomenon is called ‘self-induction’ and the emf induced is called back emf, current so produced in the coil is called induced current.
- Self-inductance of a solenoid is given by –
Where μo = Absolute permeability, N = Number of turns, l = length of the solenoid, the resistance of the coil (R) = 4Ω, and A = Area of the solenoid. - Induced e.m.f can be given as
Where ,
VL = induced voltage in volts
N = self-inductance of the coil
dI/dt = rate of change of current in ampere/second
Calculation:
Given I1 = 4A, I2 = 2A, dt = 0.05 sec, VL = 8 volt
⇒ dI = I2 - I1 = (2 - 4) = -2A
From equation 1,
Hence, option 1 is correct.
Given I1 = 4A, I2 = 2A, dt = 0.05 sec, VL = 8 volt
⇒ dI = I2 - I1 = (2 - 4) = -2A
From equation 1,
Hence, option 1 is correct.
The group delay of a wave with phase constant 2.5 units and frequency of 1.2 radian/sec is- a)3.7
- b)1.3
- c)3
- d)2.08
Correct answer is option 'D'. Can you explain this answer?
The group delay of a wave with phase constant 2.5 units and frequency of 1.2 radian/sec is
a)
3.7
b)
1.3
c)
3
d)
2.08
|
Sanskriti Bajaj answered |
Answer: d
Explanation: The group delay is given by td = β/ω. On substituting for β = 2.5 and ω = 1.2, we get the group delay as td = 2.5/1.2 = 2.08 units.
Explanation: The group delay is given by td = β/ω. On substituting for β = 2.5 and ω = 1.2, we get the group delay as td = 2.5/1.2 = 2.08 units.
The critical angle for two media with permittivities of 16 and 9 respectively is- a)48.59
- b)54.34
- c)60
- d)45
Correct answer is option 'A'. Can you explain this answer?
The critical angle for two media with permittivities of 16 and 9 respectively is
a)
48.59
b)
54.34
c)
60
d)
45
|
Kiran Iyer answered |
Answer: a
Explanation: The sine of the critical angle is the ratio of refractive index of medium 2 to that in medium 1. Thus sin θc = n2/n1. Also n = √ε, thus sin θc = √ε2/√ε1. Put ε1 = 16 and ε2 = 9, we get θc = sin-1(3/4) = 48.59 degree.
Explanation: The sine of the critical angle is the ratio of refractive index of medium 2 to that in medium 1. Thus sin θc = n2/n1. Also n = √ε, thus sin θc = √ε2/√ε1. Put ε1 = 16 and ε2 = 9, we get θc = sin-1(3/4) = 48.59 degree.
Brewster angle is valid for which type of polarisation?- a)Perpendicular
- b)Parallel
- c)S polarised
- d)P polarised
Correct answer is option 'B'. Can you explain this answer?
Brewster angle is valid for which type of polarisation?
a)
Perpendicular
b)
Parallel
c)
S polarised
d)
P polarised
|
|
Ritika Mukherjee answered |
Answer: b
Explanation: The parallel polarisation of the electromagnetic waves is possible only when the transmission occurs at the Brewster angle.
Explanation: The parallel polarisation of the electromagnetic waves is possible only when the transmission occurs at the Brewster angle.
Calculate the phase constant of a wave with skin depth of 2.5 units.- a)5/2
- b)5
- c)2
- d)2/5
Correct answer is option 'D'. Can you explain this answer?
Calculate the phase constant of a wave with skin depth of 2.5 units.
a)
5/2
b)
5
c)
2
d)
2/5
|
|
Malavika Nair answered |
Answer: d
Explanation: The skin depth is the reciprocal of the phase constant and the attenuation constant too. Thus δ = 1/β. On substituting for δ = 2.5, we get β = 1/δ = 1/2.5 = 2/5 units.
Explanation: The skin depth is the reciprocal of the phase constant and the attenuation constant too. Thus δ = 1/β. On substituting for δ = 2.5, we get β = 1/δ = 1/2.5 = 2/5 units.
The line integral of which parameter is zero for static fields?- a)E
- b)H
- c)D
- d)B
Correct answer is option 'A'. Can you explain this answer?
The line integral of which parameter is zero for static fields?
a)
E
b)
H
c)
D
d)
B
|
|
Charvi Reddy answered |
Answer: a
Explanation: The field is irrotational for static fields. Thus curl of E is zero. From Stokes theorem, the line integral of E is same as the surface integral of the curl of E. Since it is zero, the line integral of E will also be zero.
Explanation: The field is irrotational for static fields. Thus curl of E is zero. From Stokes theorem, the line integral of E is same as the surface integral of the curl of E. Since it is zero, the line integral of E will also be zero.
The electric field intensity of a field with velocity 10m/s and flux density of 2.8 units is- a)0.28
- b)28
- c)280
- d)10/2.8
Correct answer is option 'B'. Can you explain this answer?
The electric field intensity of a field with velocity 10m/s and flux density of 2.8 units is
a)
0.28
b)
28
c)
280
d)
10/2.8
|
Sanchita Choudhary answered |
Answer: b
Explanation: The electric field is the product of the velocity and the magnetic flux density given by E = v x B. On substituting v = 10 and B = 2.8, we get E = 10 x 2.8 = 28 units.
Explanation: The electric field is the product of the velocity and the magnetic flux density given by E = v x B. On substituting v = 10 and B = 2.8, we get E = 10 x 2.8 = 28 units.
If the conductor is stationary and the field is changing (varying), then emf induced in it. Such an emf is known as:- a)Self-induced emf
- b)Back emf
- c)Static-induced emf
- d)Dynamically-induced emf
Correct answer is option 'C'. Can you explain this answer?
If the conductor is stationary and the field is changing (varying), then emf induced in it. Such an emf is known as:
a)
Self-induced emf
b)
Back emf
c)
Static-induced emf
d)
Dynamically-induced emf
|
Imtiaz Ahmad answered |
Dynamically induced EMF: When the conductor is rotating and the field is stationary, then the emf induced in the conductor is called dynamically induced EMF.
Ex: DC Generator, AC generator
Static induced EMF: When the conductor is stationary and the field is changing (varying) then the emf induced in the conductor is called static induced EMF.
Ex: Transformer
Ex: DC Generator, AC generator
Static induced EMF: When the conductor is stationary and the field is changing (varying) then the emf induced in the conductor is called static induced EMF.
Ex: Transformer
EM waves do not travel inside metals. State True/False. - a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
EM waves do not travel inside metals. State True/False.
a)
True
b)
False
|
|
Debanshi Iyer answered |
Answer: a
Explanation: The conductors or metals do not support EM wave propagation onto them due the skin effect. This is the reason why mobile phones cannot be used inside lifts.
Explanation: The conductors or metals do not support EM wave propagation onto them due the skin effect. This is the reason why mobile phones cannot be used inside lifts.
The Snell’s law can be derived from which type of incidence?- a)Incidence angle
- b)Reflected angle
- c)Refracted angle
- d)Oblique incidence
Correct answer is option 'D'. Can you explain this answer?
The Snell’s law can be derived from which type of incidence?
a)
Incidence angle
b)
Reflected angle
c)
Refracted angle
d)
Oblique incidence
|
|
Mainak Pillai answered |
Answer: d
Explanation: The oblique incidence refers to the interface between dielectric media. Consider a planar interface between two dielectric media. A plane wave is incident at an angle from medium 1 and reflected from medium 2. The interface plane defines the boundary between the media. This is the oblique medium.
Explanation: The oblique incidence refers to the interface between dielectric media. Consider a planar interface between two dielectric media. A plane wave is incident at an angle from medium 1 and reflected from medium 2. The interface plane defines the boundary between the media. This is the oblique medium.
When the length of the solenoid is doubled without any change in the number of turns and the area of the coil.Then its self-inductance will - a)Nine times
- b)Half times
- c)Doubled
- d)Unchanged
Correct answer is option 'B'. Can you explain this answer?
When the length of the solenoid is doubled without any change in the number of turns and the area of the coil.Then its self-inductance will
a)
Nine times
b)
Half times
c)
Doubled
d)
Unchanged
|
|
Abhay Khanna answered |
Explanation:
In order to understand why the self-inductance of a solenoid halves when its length is doubled without any change in the number of turns and the area of the coil, we need to consider the formula for the self-inductance of a solenoid.
The self-inductance of a solenoid is given by the formula:
L = (μ₀N²A)/l
Where:
L = self-inductance of the solenoid
μ₀ = permeability of free space (constant)
N = number of turns in the solenoid
A = area of the cross-section of the solenoid
l = length of the solenoid
Analysis:
When the length of the solenoid is doubled, the value of 'l' in the formula is doubled.
If we substitute the new values into the formula, we get:
L' = (μ₀N²A)/(2l)
Now, let's compare the new self-inductance (L') with the original self-inductance (L):
L' = (μ₀N²A)/(2l)
L = (μ₀N²A)/l
Comparison:
To compare L' and L, we can divide L' by L:
L'/L = [(μ₀N²A)/(2l)] / [(μ₀N²A)/l]
L'/L = l / (2l)
L'/L = 1/2
This shows that the new self-inductance (L') is half of the original self-inductance (L).
Conclusion:
Therefore, when the length of a solenoid is doubled without any change in the number of turns and the area of the coil, the self-inductance of the solenoid halves.
In order to understand why the self-inductance of a solenoid halves when its length is doubled without any change in the number of turns and the area of the coil, we need to consider the formula for the self-inductance of a solenoid.
The self-inductance of a solenoid is given by the formula:
L = (μ₀N²A)/l
Where:
L = self-inductance of the solenoid
μ₀ = permeability of free space (constant)
N = number of turns in the solenoid
A = area of the cross-section of the solenoid
l = length of the solenoid
Analysis:
When the length of the solenoid is doubled, the value of 'l' in the formula is doubled.
If we substitute the new values into the formula, we get:
L' = (μ₀N²A)/(2l)
Now, let's compare the new self-inductance (L') with the original self-inductance (L):
L' = (μ₀N²A)/(2l)
L = (μ₀N²A)/l
Comparison:
To compare L' and L, we can divide L' by L:
L'/L = [(μ₀N²A)/(2l)] / [(μ₀N²A)/l]
L'/L = l / (2l)
L'/L = 1/2
This shows that the new self-inductance (L') is half of the original self-inductance (L).
Conclusion:
Therefore, when the length of a solenoid is doubled without any change in the number of turns and the area of the coil, the self-inductance of the solenoid halves.
The non existence of the magnetic monopole is due to which operation?- a)Gradient
- b)Divergence
- c)Curl
- d)Laplacian
Correct answer is option 'B'. Can you explain this answer?
The non existence of the magnetic monopole is due to which operation?
a)
Gradient
b)
Divergence
c)
Curl
d)
Laplacian
|
Devansh Das answered |
Answer: b
Explanation: The Maxwell fourth law or the Gauss law for magnetic field states that the divergence of B is zero, implies the non existence of magnetic monopoles. Thus the operation involved is divergence.
Explanation: The Maxwell fourth law or the Gauss law for magnetic field states that the divergence of B is zero, implies the non existence of magnetic monopoles. Thus the operation involved is divergence.
The reflection coefficient is 0.5. Find the return loss.- a)12.12
- b)-12.12
- c)6.02
- d)-6.02
Correct answer is option 'C'. Can you explain this answer?
The reflection coefficient is 0.5. Find the return loss.
a)
12.12
b)
-12.12
c)
6.02
d)
-6.02
|
|
Saumya Sen answered |
Answer: c
Explanation: The return loss is given by RL = -20log R, where is the reflection coefficient. It is given as 0.5. Thus the return loss will be RL = -20 log 0.5 = 6.02 decibel.
Explanation: The return loss is given by RL = -20log R, where is the reflection coefficient. It is given as 0.5. Thus the return loss will be RL = -20 log 0.5 = 6.02 decibel.
The expression for velocity of a wave in the conductor is- a)V = √(2ω/μσ)
- b)V = √(2ωμσ)
- c)V = (2ω/μσ)
- d)V = (2ωμσ)
Correct answer is option 'A'. Can you explain this answer?
The expression for velocity of a wave in the conductor is
a)
V = √(2ω/μσ)
b)
V = √(2ωμσ)
c)
V = (2ω/μσ)
d)
V = (2ωμσ)
|
|
Nayanika Kaur answered |
Answer: a
Explanation: The velocity is the ratio of the frequency to the phase constant. In conductors, the phase constant is given by √(ωμσ/2). On substituting for β,ω in v, we get v = √(2ω/μσ) units
Explanation: The velocity is the ratio of the frequency to the phase constant. In conductors, the phase constant is given by √(ωμσ/2). On substituting for β,ω in v, we get v = √(2ω/μσ) units
When the polarisation of the receiving antenna is unknown, to ensure that it receives atleast half the power, the transmitted wave should be- a)Linearly polarised
- b)Elliptically polarised
- c)Circularly polarised
- d)Normally polarised
Correct answer is option 'C'. Can you explain this answer?
When the polarisation of the receiving antenna is unknown, to ensure that it receives atleast half the power, the transmitted wave should be
a)
Linearly polarised
b)
Elliptically polarised
c)
Circularly polarised
d)
Normally polarised
|
|
Samarth Khanna answered |
Answer: c
Explanation: The polarisation of the transmitting and receiving antenna has to be the same. This is the condition for maximum power transfer to occur. This is possible only when the polarisation is circular.
Explanation: The polarisation of the transmitting and receiving antenna has to be the same. This is the condition for maximum power transfer to occur. This is possible only when the polarisation is circular.
The Snell law is applicable for perpendicular polarisation and the Brewster law is applicable for parallel polarisation. State True/False.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
The Snell law is applicable for perpendicular polarisation and the Brewster law is applicable for parallel polarisation. State True/False.
a)
True
b)
False
|
|
Kritika Gupta answered |
Answer: a
Explanation: The Snell law is calculated from the oblique incidence media. Thus it is applicable for perpendicular polarisation. The Brewster law is applicable for perpendicular polarisation.
Explanation: The Snell law is calculated from the oblique incidence media. Thus it is applicable for perpendicular polarisation. The Brewster law is applicable for perpendicular polarisation.
The transmission coefficient of a wave with incident and transmitted electric field of 5 and 5 respectively is- a)0
- b)1
- c)10
- d)5
Correct answer is option 'B'. Can you explain this answer?
The transmission coefficient of a wave with incident and transmitted electric field of 5 and 5 respectively is
a)
0
b)
1
c)
10
d)
5
|
|
Aditya Basu answered |
Answer: b
Explanation: The transmission coefficient is the ratio of the transmitted electric field to the incident electric field. Thus T = Et/Ei. On substituting for Et = 5 and Ei = 5, we get T = 5/5 = 1(no unit). Simply, when the incident and transmitted field are same, no reflection occurs and the transmission is unity.
Explanation: The transmission coefficient is the ratio of the transmitted electric field to the incident electric field. Thus T = Et/Ei. On substituting for Et = 5 and Ei = 5, we get T = 5/5 = 1(no unit). Simply, when the incident and transmitted field are same, no reflection occurs and the transmission is unity.
The phase shift in the electric and magnetic fields in an EM wave is given by which parameter?- a)phase constant
- b)attenuation constant
- c)propagation constant
- d)intrinsic impedance
Correct answer is option 'D'. Can you explain this answer?
The phase shift in the electric and magnetic fields in an EM wave is given by which parameter?
a)
phase constant
b)
attenuation constant
c)
propagation constant
d)
intrinsic impedance
|
|
Nishtha Chauhan answered |
Answer: d
Explanation: The intrinsic impedance in a conductor is given by η = √(ωμ/2σ) x (1+j). The phase shift is represented by the 1+j term. In polar form it indicates 45 degree phase shift.
Explanation: The intrinsic impedance in a conductor is given by η = √(ωμ/2σ) x (1+j). The phase shift is represented by the 1+j term. In polar form it indicates 45 degree phase shift.
The benefit of Maxwell equation is that- a)Any parameter can be calculated
- b)Antenna can be designed
- c)Polarisation of the wave can be calculated
- d)Transmission line constants can be found
Correct answer is option 'A'. Can you explain this answer?
The benefit of Maxwell equation is that
a)
Any parameter can be calculated
b)
Antenna can be designed
c)
Polarisation of the wave can be calculated
d)
Transmission line constants can be found
|
|
Uday Saini answered |
Answer: a
Explanation: The Maxwell equation relates the parameters E, D, H, B. When one parameter is known the other parameters can be easily calculated. In other words, it is used to relate an electric field parameter with its equivalent magnetic field.
Explanation: The Maxwell equation relates the parameters E, D, H, B. When one parameter is known the other parameters can be easily calculated. In other words, it is used to relate an electric field parameter with its equivalent magnetic field.
Which one of the following laws will not contribute to the Maxwell’s equations?- a)Gauss law
- b)Faraday law
- c)Ampere law
- d)Curie Weiss law
Correct answer is option 'D'. Can you explain this answer?
Which one of the following laws will not contribute to the Maxwell’s equations?
a)
Gauss law
b)
Faraday law
c)
Ampere law
d)
Curie Weiss law
|
|
Siddharth Khanna answered |
Answer: d
Explanation: The Gauss law, Faraday law and the Ampere law are directly used to find the parameters E, H, D, B. Thus it contributes to the Maxwell equations. The Curie Weiss law pertains to the property of any magnetic material. Thus it is not related to the Maxwell equation.
Explanation: The Gauss law, Faraday law and the Ampere law are directly used to find the parameters E, H, D, B. Thus it contributes to the Maxwell equations. The Curie Weiss law pertains to the property of any magnetic material. Thus it is not related to the Maxwell equation.
The radiation resistance of an antenna having a power of 120 units and antenna current of 5A is- a)4.8
- b)9.6
- c)3.6
- d)1.8
Correct answer is option 'A'. Can you explain this answer?
The radiation resistance of an antenna having a power of 120 units and antenna current of 5A is
a)
4.8
b)
9.6
c)
3.6
d)
1.8
|
|
Nandita Kulkarni answered |
Answer: a
Explanation: The power of an antenna is given by Prad = Ia2 Rrad, where Ia is the antenna current and Rrad is the radiation resistance. On substituting the given data, we get Rrad = Prad/Ia2 = 120/52 = 4.8 ohm.
Explanation: The power of an antenna is given by Prad = Ia2 Rrad, where Ia is the antenna current and Rrad is the radiation resistance. On substituting the given data, we get Rrad = Prad/Ia2 = 120/52 = 4.8 ohm.
The numerical aperture of a material with acceptance angle of 60 degree in water will be- a)1.15
- b)2.15
- c)5.21
- d)1.52
Correct answer is option 'A'. Can you explain this answer?
The numerical aperture of a material with acceptance angle of 60 degree in water will be
a)
1.15
b)
2.15
c)
5.21
d)
1.52
|
|
Puja Shah answered |
Answer: a
Explanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is 1.33 for water medium. Given that the acceptance angle is 60, we get NA = 1.33 sin 60 = 1.15.
Explanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is 1.33 for water medium. Given that the acceptance angle is 60, we get NA = 1.33 sin 60 = 1.15.
The Snell’s law is given by- a)N1 sin θi = N2 sin θt
- b)N2 sin θi = N1 sin θt
- c)sin θi = sin θt
- d)N1 cos θi = N2 cos θt
Correct answer is option 'A'. Can you explain this answer?
The Snell’s law is given by
a)
N1 sin θi = N2 sin θt
b)
N2 sin θi = N1 sin θt
c)
sin θi = sin θt
d)
N1 cos θi = N2 cos θt
|
|
Prisha Iyer answered |
Answer: a
Explanation: The Snell law states that in an oblique medium, the product of the refractive index and sine of incidence angle in medium 1 is same as that of medium 2. Thus it is given by N1 sin θi = N2 sin θt.
Explanation: The Snell law states that in an oblique medium, the product of the refractive index and sine of incidence angle in medium 1 is same as that of medium 2. Thus it is given by N1 sin θi = N2 sin θt.
The transmission coefficient is given by 0.65. Find the return loss of the wave.- a)9.11
- b)1.99
- c)1.19
- d)9.91
Correct answer is option 'A'. Can you explain this answer?
The transmission coefficient is given by 0.65. Find the return loss of the wave.
a)
9.11
b)
1.99
c)
1.19
d)
9.91
|
|
Lakshmi Desai answered |
Answer: a
Explanation: The transmission coefficient is the reverse of the reflection coefficient, i.e, T + R = 1. When T = 0.65, we get R = 0.35. Thus the return loss RL = -20log R = -20log 0.35 = 9.11 decibel.
Explanation: The transmission coefficient is the reverse of the reflection coefficient, i.e, T + R = 1. When T = 0.65, we get R = 0.35. Thus the return loss RL = -20log R = -20log 0.35 = 9.11 decibel.
Find the relative permittivity of the medium having a refractive index of 1.6- a)0.4
- b)2.56
- c)3.2
- d)4.8
Correct answer is option 'B'. Can you explain this answer?
Find the relative permittivity of the medium having a refractive index of 1.6
a)
0.4
b)
2.56
c)
3.2
d)
4.8
|
|
Niti Tiwari answered |
Answer: b
Explanation: The refractive index is the square root of the relative permittivity. It is given by n = √εr. To get εr, put n = 1.6. We get εr = n2 = 1.62 = 2.56(no unit).
Explanation: The refractive index is the square root of the relative permittivity. It is given by n = √εr. To get εr, put n = 1.6. We get εr = n2 = 1.62 = 2.56(no unit).
An implication of the continuity equation of conductors is given by- a)J = σ E
- b)J = E/σ
- c)J = σ/E
- d)J = jwEσ
Correct answer is option 'A'. Can you explain this answer?
An implication of the continuity equation of conductors is given by
a)
J = σ E
b)
J = E/σ
c)
J = σ/E
d)
J = jwEσ
|
|
Mansi Datta answered |
Answer: a
Explanation: The continuity equation indicates the current density in conductors. This is the product of the conductivity of the conductor and the electric field subjected to it. Thus J = σE is the implication of the continuity equation for conductors.
Explanation: The continuity equation indicates the current density in conductors. This is the product of the conductivity of the conductor and the electric field subjected to it. Thus J = σE is the implication of the continuity equation for conductors.
Which of the following law states that “whenever the magnetic flux linked with a conductor or coil changes, an emf is induced in it?- a)Fleming’s right hand rule
- b)Faraday’s first law of electromagnetic induction
- c)Lenz’s law
- d)Faraday’s second law of electromagnetic induction
Correct answer is option 'B'. Can you explain this answer?
Which of the following law states that “whenever the magnetic flux linked with a conductor or coil changes, an emf is induced in it?
a)
Fleming’s right hand rule
b)
Faraday’s first law of electromagnetic induction
c)
Lenz’s law
d)
Faraday’s second law of electromagnetic induction
|
|
Imtiaz Ahmad answered |
Faraday's laws: Faraday performed many experiments and gave some laws about electromagnetism.
Faraday's First Law:
Whenever a conductor is placed in a varying magnetic field an EMF gets induced across the conductor (called induced emf), and if the conductor is a closed circuit then induced current flows through it.
A magnetic field can be varied by various methods:
Faraday's First Law:
Whenever a conductor is placed in a varying magnetic field an EMF gets induced across the conductor (called induced emf), and if the conductor is a closed circuit then induced current flows through it.
A magnetic field can be varied by various methods:
- By moving magnet
- By moving the coil
- By rotating the coil relative to a magnetic field
Faraday's second law of electromagnetic induction states that the magnitude of induced emf is equal to the rate of change of flux linkages with the coil.
According to Faraday's law of electromagnetic induction, the rate of change of flux linkages is equal to the induced emf:
According to Faraday's law of electromagnetic induction, the rate of change of flux linkages is equal to the induced emf:
Which quantity is solenoidal in the electromagnetic theory?- a)Electric field intensity
- b)Electric flux density
- c)Magnetic field intensity
- d)Magnetic flux density
Correct answer is option 'D'. Can you explain this answer?
Which quantity is solenoidal in the electromagnetic theory?
a)
Electric field intensity
b)
Electric flux density
c)
Magnetic field intensity
d)
Magnetic flux density
|
|
Tarun Chawla answered |
Answer: d
Explanation: The divergence of the magnetic flux density is zero. This is the Maxwell fourth equation. As the divergence is zero, the quantity will be solenoidal or divergent less.
Explanation: The divergence of the magnetic flux density is zero. This is the Maxwell fourth equation. As the divergence is zero, the quantity will be solenoidal or divergent less.
In dielectric medium, the Maxwell second equation becomes- a)Curl(H) = Jd
- b)Curl(H) = Jc
- c)Curl(E) = Jd
- d)Curl(E) = Jd
Correct answer is option 'A'. Can you explain this answer?
In dielectric medium, the Maxwell second equation becomes
a)
Curl(H) = Jd
b)
Curl(H) = Jc
c)
Curl(E) = Jd
d)
Curl(E) = Jd
|
|
Sakshi Roy answered |
Answer: a
Explanation: In dielectric medium conductivity σ will be zero. So the current density has only the displacement current density. Thus the Maxwell equation will be Curl(H) = Jd.
Explanation: In dielectric medium conductivity σ will be zero. So the current density has only the displacement current density. Thus the Maxwell equation will be Curl(H) = Jd.
Find the electric field applied on a system with electrons having a velocity 5m/s subjected to a magnetic flux of 3.6 units.- a)15
- b)18
- c)1.38
- d)0.72
Correct answer is option 'B'. Can you explain this answer?
Find the electric field applied on a system with electrons having a velocity 5m/s subjected to a magnetic flux of 3.6 units.
a)
15
b)
18
c)
1.38
d)
0.72
|
|
Vaibhav Mukherjee answered |
Answer: b
Explanation: The electric field intensity is the product of the velocity and the magnetic flux density. Thus E = v x B, on substituting v = 5 and B = 3.6, we get E = 5 x 3.6 = 18 units.
Explanation: The electric field intensity is the product of the velocity and the magnetic flux density. Thus E = v x B, on substituting v = 5 and B = 3.6, we get E = 5 x 3.6 = 18 units.
An air-core radio-frequency transformer as shown has a primary winding and a secondary winding. The mutual inductance M between the windings of the transformer is ______ μH.
(Round off to 2 decimal places.)
Correct answer is between '50,52'. Can you explain this answer?
An air-core radio-frequency transformer as shown has a primary winding and a secondary winding. The mutual inductance M between the windings of the transformer is ______ μH.
(Round off to 2 decimal places.)
(Round off to 2 decimal places.)
|
|
Pooja Patel answered |
Concept:
Mutual Inductance:
When two coils are placed close to each other, a change in current in the first coil produces a change in magnetic flux, which cuts not only the coil itself but also the second coil as well. The change in the flux induces a voltage in the second coil, this voltage is called induced voltage and the two coils are said to have a mutual inductance.
Consider a pair of coupled inductors with self-inductance L1 and L2, magnetically coupled through coupling coefficient k.
Input and output voltage expressions are given as
V1 = jωL1I1 + jωMI2 ...(1)
V2 = jωL2I2 + jωMI1 ...(2)
Where,
ω = 2πf
M = Mutual inductance
L1 = Inductance of coil one
L2 = Inductance of coil two
Calculation:
In the given circuit secondary is open-circuited, so I2 = 0 A
Given secondary voltage V2 = 7.3 Vp-p
The output voltage expression from equation(2) is given as
V2 = jωMI1 ....(3)
The given voltage across the 22 Ω resistor is 5 Vp-p
So primary current is calculated as I1 = 5 / 22 Ap-p
From equation(3)
|V2| = 2π f M I1
7.3 = 2 × π × 100 × 103 × M × (5/22)
M = 51.12 μH
Mutual Inductance:
When two coils are placed close to each other, a change in current in the first coil produces a change in magnetic flux, which cuts not only the coil itself but also the second coil as well. The change in the flux induces a voltage in the second coil, this voltage is called induced voltage and the two coils are said to have a mutual inductance.
Consider a pair of coupled inductors with self-inductance L1 and L2, magnetically coupled through coupling coefficient k.
Input and output voltage expressions are given as
V1 = jωL1I1 + jωMI2 ...(1)
V2 = jωL2I2 + jωMI1 ...(2)
Where,
ω = 2πf
M = Mutual inductance
L1 = Inductance of coil one
L2 = Inductance of coil two
Calculation:
In the given circuit secondary is open-circuited, so I2 = 0 A
Given secondary voltage V2 = 7.3 Vp-p
The output voltage expression from equation(2) is given as
V2 = jωMI1 ....(3)
The given voltage across the 22 Ω resistor is 5 Vp-p
So primary current is calculated as I1 = 5 / 22 Ap-p
From equation(3)
|V2| = 2π f M I1
7.3 = 2 × π × 100 × 103 × M × (5/22)
M = 51.12 μH
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