Physics: CUET Mock Test - 3 - CUET MCQ

# Physics: CUET Mock Test - 3 - CUET MCQ

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## 40 Questions MCQ Test CUET Mock Test Series - Physics: CUET Mock Test - 3

Physics: CUET Mock Test - 3 for CUET 2024 is part of CUET Mock Test Series preparation. The Physics: CUET Mock Test - 3 questions and answers have been prepared according to the CUET exam syllabus.The Physics: CUET Mock Test - 3 MCQs are made for CUET 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Physics: CUET Mock Test - 3 below.
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Physics: CUET Mock Test - 3 - Question 1

### When is the magnetic flux said to be negative?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 1

If the normal points in the opposite direction of the field, then θ = 180o and the flux is taken as negative. If the magnetic field is pointing opposite the direction of the surface area then the value of this flux is negative.

Physics: CUET Mock Test - 3 - Question 2

### Identify the expression for the motional electromotive force from the following?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 2

Motional electromotive is the emf induced by the motion of the conductor across the magnetic field. The expression for motional electromotive force is given by:
E = -vLB
This equation is true as long as the velocity, magnetic field, and length are mutually perpendicular to each other. The negative sign is associated with Lenz’s law.

Physics: CUET Mock Test - 3 - Question 3

### What is the reactance of an inductor in a dc circuit?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 3

The reactance of an inductor in a dc circuit is zero.
For dc → f = 0
XL = 2π f L
XL = 0
Therefore, the reactance of an inductor in a dc circuit is zero.

Physics: CUET Mock Test - 3 - Question 4

How many types of power can be defined in an AC circuit?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 4

In an AC circuit, we can define three types of power, namely, Instantaneous power, Average power, and Apparent power. A circuit element produces or dissipates power according to the equation → P = IV, where I is the current through the element and V is the voltage across it.

Physics: CUET Mock Test - 3 - Question 5

Which among the following is true about transformers?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 5

Transformers are used to convert low alternating voltage to a high alternating voltage and vice versa. Transformers are based on the phenomena of mutual induction. A transformer consists of a soft iron coil with two coils wound around it which are not connected to one another. The other statements are not valid.

Physics: CUET Mock Test - 3 - Question 6

Identify the factor on which the angle of deviation of the prism does not depend.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 6

Factors on which the angle of deviation depends are → the angle of incidence, the material of the prism, the wavelength of light used, and the angle of the prism. So, the factor on which the angle of deviation that does not depend on is the angle of reflection.

Physics: CUET Mock Test - 3 - Question 7

A bar of length 0.7 m slides along metal rails at a speed of 1 m/s. The bar and rails are in a magnetic field of 20 T, pointing out into the page. Calculate the motional emf.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 7

Length (L) = 0.7 m; Speed (v) = 1 m/s; Magnetic field (B) = 20 T
The required equation E = -vLB (The negative sign only applies to the direction)
E = 1 × 0.7 × 20
E = 0.7 × 20
E = 14 V
Therefore, the motional emf in the bar and rails is 14 V.

Physics: CUET Mock Test - 3 - Question 8

In which type of circuit the value of power factor will be minimum?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 8

For a purely inductive circuit, Φ = ± (π/2)
Power factor = cos (±(π/2))
Power factor = 0
Therefore, the power factor will be minimum for an inductive circuit.

Physics: CUET Mock Test - 3 - Question 9

Which among the following varies in both magnitude and sign over a cycle?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 9

Instantaneous power is defined as the power in an AC circuit at any instant of time. It is equal to the product of values of alternating voltage and alternating current at that time. And, because instantaneous power varies in both magnitude and sign over a cycle, it seldom has any practical importance.

Physics: CUET Mock Test - 3 - Question 10

Calculate the refractive index of the material of an equilateral prism for which the angle of minimum deviation is 60°.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 10

Refractive index of the prism material is μ =

μ = √3.

Physics: CUET Mock Test - 3 - Question 11

A bar of length 0.15 m slides along metal rails at a speed of 5 m/s. The bar and rails are in a magnetic field of 40 T, pointing out into the page. The resistance of two resistors in parallel is both 20 Ω, and the resistance of the bar is 5 Ω. What is the current in the bar?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 11

L = 0.15 m; B = 40 T; v = 5 m/s; R1 = 10 Ω; R2 = 10 Ω; R3 = 5 Ω
Emf (E) = vLB = 5 × 0.15 × 40
E = 5 × 6
E = 30 V
R1 and R2 are in parallel ➔
RTOT = R + R3 = 10 + 5 = 15 Ω
Therefore, current (I) = E/R
I = 30/15
I = 2 A

Physics: CUET Mock Test - 3 - Question 12

The frequency of ac is doubled. How does XL get affected?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 12

When the frequency of an ac is doubled → The inductive reactance (XL) gets doubled.
This is because inductive reactance is directly proportional to the frequency of an alternating current circuit.

Physics: CUET Mock Test - 3 - Question 13

Identify the expression for average power.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 13

Average power can be defined as the power averaged over one full cycle of alternating current. It is also known as true power. The expression for average power is given by:
Pav=VrmsIrmscos⁡Φ = (V0I0/2)(cosΦ)

Physics: CUET Mock Test - 3 - Question 14

Pick out the correct combination for a step-up transformer.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 14

For a step-up transformer, the voltage at the second terminal is greater than the primary terminal, i.e. → Vs > Vp. Similarly, the current in the secondary coil is lesser than that current flowing the primary coil, i.e. → Is < Ip. Also, the number of turns in the secondary winding is greater than that in the primary winding, i.e. → Ns > Np. So the transformation ratio will be greater than 1. So, the correct combination is given as:
k > 1; Vs > Vp, Is < Ip, Ns > Np

Physics: CUET Mock Test - 3 - Question 15

Which of the following causes dispersion?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 15

The reason is that for a given angle f incidence, the reflection is the same for all the wavelengths of white light while the angle of refraction is different for different wavelengths. Therefore, this is how dispersion is caused.

Physics: CUET Mock Test - 3 - Question 16

What is the use of a Van de Graff generator?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 16

Van de Graff generator is used to create a large amount of static electricity. A Van de Graff generator uses static electricity and a moving belt to charge a large metal sphere to a very high voltage. As the belt moves, electrons move from the rubber belt to the silicon roller, causing the belt to become positively charged and the roller to become negatively charged. As a result, it builds up positive charge.

Physics: CUET Mock Test - 3 - Question 17

At what frequency will a coil, which has an inductance of 2.5 H, have a reactance of 3500 Ω?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 17

f = XL/2πL
f = 3500/(2×3.14×2.5)
f = 222.9 Hz ≈ 223 Hz
Therefore, the frequency of a coil having reactance of 3500 Ω is 223 Hz.

Physics: CUET Mock Test - 3 - Question 18

What is the order of potential difference built up by the Van de Graff generator?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 18

A Van de Graff generator, by means of a moving belt and suitable brushes, transfers charge continuously to a large spherical conducting shell. As a result, a potential difference of the order of several million volts is built up and this can be used for accelerating charged particles.

Physics: CUET Mock Test - 3 - Question 19

When was Van de Graff generator invented and by whom?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 19

Van de Graff generator was invented by Robert Jemison Van de Graff on November 28, 1933. Robert Jemison invented the Van de Graff generator, which is a kind of high-voltage electrostatic generator that accelerates particles, while he was doing his PhD in Princeton University.

Physics: CUET Mock Test - 3 - Question 20

What happens to the frequency and the wavelength when light passes from a rarer to a denser medium?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 20

When light passes from a rarer to a denser medium, the wavelength of light changes but the frequency remains unchanged. Therefore, there is no change in the frequency of light, only the wavelength changes.

Physics: CUET Mock Test - 3 - Question 21

A bar of length 2m is said to fall freely in a magnetic field of magnitude 50 T. What is the motional emf in the bar when it has fallen 40 meters?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 21

Given: L = 2 m; B = 50 T;
The bar is said to be falling freely, so → u = 0
According to Newton’s third equation → v2 – u2 = 2gh
v2 = 2gh; h = 40 m

v = 28 m/s
Motional emf (E) = vLB
E = 28 × 2 × 50
E = 2800 V

Physics: CUET Mock Test - 3 - Question 22

Why does an inductor offer an easy path to dc and a resistive path to ac?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 22

For dc, f = 0,
XL = 2π f L
XL = 0
XL is zero for dc and has a finite value for ac Hence an inductor offers an easy path to dc and a resistive path to ac.

Physics: CUET Mock Test - 3 - Question 23

Which of the following is true about power factor?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 23

The power factor of an AC electrical power system is defined as the ratio of the real or true power absorbed by the load to the apparent power flowing in the circuit, and in the closed interval of −1 to 1. The expression for power factor is given as:
cos⁡Φ = (True power/Apparent power)

Physics: CUET Mock Test - 3 - Question 24

Identify the correct combination for a step-down transformer.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 24

For a step-down transformer, the voltage at the second terminal is lesser than the primary terminal, i.e. → Vs < Vp. Similarly, the number of turns in the secondary winding is lesser than that in the primary winding, i.e. → Ns < Np. Also, the current in the secondary coil is greater than that current flowing the primary coil, i.e. → Is > Ip. So the transformation ratio will be lesser than 1. So, the correct combination is given as:
k < 1; Vs < Vp, Is > Ip, Ns < Np

Physics: CUET Mock Test - 3 - Question 25

What is the relative refractive index of water with respect to glass?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 25

Absolute refractive index = (Speed of light in vacuum/Speed of light in the medium). The relative refractive index of water with respect to glass is less than unity.

Physics: CUET Mock Test - 3 - Question 26

A metal rod is forced to move with constant velocity along two parallel metal rails, connected with a strip of metal at one end across a magnetic field (B) of 0.5 T, pointing out of the page. The rod is of length 45 cm and the speed of the rod is 70 cm/s. The rod has a resistance of 10 Ω and the resistance of the rails and connector is negligible. What is the rate at which energy is being transferred to thermal energy?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 26

Given: B = 0.5 T; v = 70 cm/s = 70 × 10-2 m/s; L = 45 cm = 45 × 10-2 m; R = 10 Ω
Motional emf (E) = vLB = 70 × 10-2 × 45 × 10-2 × 0.5
E = 0.15 V
Current (I) = E/R
I = 0.15/10
I = 0.015 A
Rate of energy or power (P) = I2R
P = 0.0152 × 10
P = 2.25 × 10-3 W
Therefore, the rate of energy transfer is 2.25 × 10-3 W.

Physics: CUET Mock Test - 3 - Question 27

Identify the type of materials which have resistivities in the range of 10-8 Ωm to 10-6 Ωm.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 27

Conductors have low resistivities in the range of 10-8 Ωm to 10-6 Ωm. Metals are good conductors. Conductors are objects or types of material that allows the flow of charge in one or more directions, and a result, the resistance offered against the flow of charge will be less.

Physics: CUET Mock Test - 3 - Question 28

What is the power factor in a pure resistive circuit?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 28

A circuit containing only a pure resistance in an AC circuit is known as a pure resistive AC Circuit. For a purely resistive circuit, the power factor is one, because the reactive power equals zero, i.e.
Φ = 0 → Power factor (cos⁡0)=1

Physics: CUET Mock Test - 3 - Question 29

Which of the following is usually taken to make the core of a transformer?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 29

Core of a transformer is used to transfer the flux produced by primary coils of transformer to secondary coils of a transformer. Therefore, the core of a transformer is made of soft iron because it has high permeability so it provides complete linkage of magnetic flux of the primary coil to the secondary coil.

Physics: CUET Mock Test - 3 - Question 30

Identify the material whose resistivity is more than 1014 Ωm.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 30

Insulators are materials which do not conduct electric current, and thereby, offer high resistance to the flow of charges. Insulators like bakelite and hard rubber have very high resistivities in the range of 1014 to 1016 Ωm.

Physics: CUET Mock Test - 3 - Question 31

Find the true statement.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 31

Motional emf is directly proportional to the magnetic field across which the electric conductor moves. It is also directly proportional to the (velocity/speed) of the electric conductor as well as to the length of the conductor. All the other statements are not valid.

Physics: CUET Mock Test - 3 - Question 32

Determine the peak current if an inductor of inductance 500 mH is connected to an ac source of peak emf 650 V and frequency 100 Hz

Detailed Solution for Physics: CUET Mock Test - 3 - Question 32

Peak current (I0) = E0/XL
I0 = (650/(2×3.14×100×0.5))
I0 = 2.07 A
Therefore, the peak current is calculated as 2.07 A.

Physics: CUET Mock Test - 3 - Question 33

What is the power factor in a pure inductive or capacitive circuit?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 33

A circuit which contains only inductance is called a pure inductive circuit and a circuit containing only a pure capacitor is known as a pure capacitive circuit. In a pure inductive circuit or a pure capacitive circuit, the current is lagging or ahead by 90 degrees from the voltage. The power factor is the cosine of the angle between the voltage and the current. Therefore:
Φ = (π/2) → Power factor (cos⁡(π/2)) = 0

Physics: CUET Mock Test - 3 - Question 34

A transformer has an efficiency of 60% and works at 5kW. If the secondary voltage is 150 V, then what is the secondary current?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 34

Given: efficiency (η) = 60%; Input power (Pi) = 5 kW = 5000 W; VS = 150 V
Efficiency (η) = (Output power(Po)/Input power(Pi)) = VsIs/VpIp

Thus,

Therefore, the current in the secondary coil is 20 A.

Physics: CUET Mock Test - 3 - Question 35

What will be the color of the sky in the absence of the atmosphere?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 35

The sunlight will not be scattered in the absence of the atmosphere. So the sky will appear dark. So, the sky will no longer be blue in the absence of an atmosphere.

Physics: CUET Mock Test - 3 - Question 36

Find out the rms value of current in the circuit wherein a 35 mH inductor is connected to 200 V, 70 Hz ac supply.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 36

XL = 2π f L
XL = 2π × 70 × 35 × 10-3 Ω.

Irms = 12.99 A ≈ 13 A
Therefore, the rms value of current in the circuit is 13 A.

Physics: CUET Mock Test - 3 - Question 37

Find the resistance value of the carbon resistor if the colors of the four bands are red, red, red and silver respectively.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 37

A color code is used to indicate the resistance value of a carbon resistor and its percentage accuracy. The corresponding value of resistance for the given color code is 22 × 102 Ω ± 10% (Red-2; Red-2; Red-2; Silver-10%)

Physics: CUET Mock Test - 3 - Question 38

‘X’ is a type of commercial resistor made from a mixture of clay, carbon black, and resin binder which are pressed and then molded into cylindrical rods by heating. Identify X.

Detailed Solution for Physics: CUET Mock Test - 3 - Question 38

Carbon resistors are made from a mixture of carbon black, clay and resin binder which are pressed and then molded into cylindrical rods by heating. The rods are enclosed in a ceramic or plastic jacket. They are used in circuits of radio receivers, amplifiers, etc.

Physics: CUET Mock Test - 3 - Question 39

On what factor does the normal shift through a refracting medium depend?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 39

The normal shift depends on the thickness of the refracting medium and the refractive index of the material. The normal shift does not depend on the angle of the prism, angle of deviation, and convection.

Physics: CUET Mock Test - 3 - Question 40

What is the power factor for a series LCR circuit at resonance?

Detailed Solution for Physics: CUET Mock Test - 3 - Question 40

The impedance for a series LCR circuit is given as:
Z =  and cos⁡Φ = R/Z
At resonance, XL= XC → Z = R;
So, the total impedance of the circuit is only due to resistor. The phase angle between voltage and current is zero. Therefore, Φ = 0 → Power factor (cosΦ) = 1

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