Physics: Topic-wise Test- 8 - NEET MCQ

Let q charge is situated at themidposition of the lineAB.The distance between AB is x. A and B be the positions of charges Q and Q respectively.

E = F/q = KQ/r²

Electric Field Intensity E = F\q

E = F/q

E =F/q = (KQ/r²)

When a tangent is drawn at any point on field line then that tangent gives the direction of electric field at that point

Only alpha rays are moving with small velocity and having charge so they will be affected by electric field.
X Rays and Gamma Rays are electromagnetic radiations. They do not carry electric charge while neutron is a charge less particle.

In a parallel plate capacitor the capacity of capacitor.

The capacity of capacitor increases if area of the plate is increased.

When key K is kept closed, condenser C is charged to potential V. When plates of capacitors are moved apart, its capacitance, C = ϵ_oA/d decreases.
As potential of condenser remains same, charge Q = CV decreases. So option is correct. Once key K is closed, condenser gets charged, Q = CV.
Now, if key K is opened, battery is disconnected, no more charging can occur i.e. Q remains same.
As plates or capacitor are moved apart, its capacity C = ϵ_oA/d decreases.
Therefore, its potential, V = q/C increases

Magnetic field part of a harmonic electromagnetic wave in vacuum
,B₀​=510×10⁻⁹T
Speed of light,
C=3×10⁸m/s
E=cB_o​=153N/C

TV signals being of high frequency are not reflected by the ionosphere. Therefore, to reflect these signals, satellites are needed. That is why, satellites are used for long distance TV transmission.
 Most long-distance shortwave (high frequency) radio communication—between 3 and 30 MHz—is a result of skywave propagation.
This 3-30 MHz is a range of frequencies which are used in sky waves propagation so that the ionosphere is capable of reflecting it.

Long distance radio broadcasts use shortwave bands because only these bands can be refracted by the ionosphere.

Maxwell’s Fourth Equation
It is based on Ampere’s circuital law. To understand Maxwell’s fourth equation it is crucial to understand Ampere’s circuital law,
Consider a wire of current-carrying conductor with the current I, since there is an electric field there has to be a magnetic field vector around it. Ampere’s circuit law states that “The closed line integral of magnetic field vector is always equal to the total amount of scalar electric field enclosed within the path of any shape” which means the current flowing along the wire(which is a scalar quantity) is equal to the magnetic field vector (which is a vector quantity)

The direction of propagation of the electromagnetic wave is always perpendicular to the plane in which
So, the direction of the propagation of the wave, 
Hence, option B is the correct answer.

Infrared waves are emitted by hot bodies. They are produced due to the de-excitation of atoms.
They are called Heat waves as they produce heat falling on matter. This is because water molecules present in most materials readily absorb infrared waves. After absorption, their thermal motion increases, that is, they heat up and heat their surroundings.
Uses: Infra red lamps; play an important role in maintaining warmth through greenhouse effect.

A body at temperature T produces a continuous spectrum of wavelengths. For a black body, the wavelength corresponding to maximum intensity of radiation is given according to Planck's law by the relation, m=0.29cmK/T. For m=106m,T=2900K.Temperatures for other wavelengths can be found. These numbers tell us the temperature ranges required for obtaining radiations in different parts of the electromagnetic spectrum. Thus, to obtain visible radiation, say  =5×107m, the source should have a temperature of about 6000K. A lower temperature will also produce this wavelength but not the maximum intensity.

Explanation:


Region between the plates:
- The region between the plates of the capacitor is where the concept of displacement current is most crucial.
- Without displacement current, the changing electric field between the plates would not be taken into account, leading to significant errors in the calculation of the magnetic field in this region.
- Displacement current ensures that Ampere's law is correctly applied in this region, considering both the current in the circuit and the changing electric field between the plates.
 

l=500sin(100πt)
⟹ω=100π
ω=2πf
⟹2πf=100π
f=50Hz
 

We know: Vrms​=​Vo​​/√2
 
Substituting values (Here RMS Voltage is 220 V)
We get: Maximum V (or amplitude) =311V
 

For alternating current average value is taken for half cycles only,
Let, I=I0sinωt where ω=2π/T

=[(I₀/ω) cosωt]_o^T/2 x 2/T
I_avg=2I_o/ π

Given peak potential is 200v
so, amplitude is 200
and frequency is 50Hz
so angular frequency is 2.πx50 = 314/sec
so the value is
E = 200sin(314t)
Hence option B is the correct answer.

E= ε_ocos(ωt+π/3) –1
I=I₀sin(ωt)=I₀cos{(π/2)-cot)
 =I0cos(ωt+(- π/2)) —2
By,1 and 2,
Phase difference between E and I,
=ϕ_E-V_I
=(ωt+π/3)- (ωt+(- π/2))
= π/3+ π/2
=5π/6

We know that,
X_L= ωL
Or, X_L =2πfL   [ ω can be written as, 2πf]
Initially,
X_L1=2πf₁L₁=1000Ω
For the second case,
F  and L both are doubled, so,
X_L2 =2π2f₁2L₁ =4x2πf₁L₁
                        =4000 Ω

R=1W
X_L=1000W
X_C=1000W
Z= Z= √ (R²+(X_L-X_C)²)
  =√(1²+(1000-1000)²)
Z=1W
    I=V/Z=100/1
I=1000A
 

L =0.14
E=100sin(100t)
⇒X_L​=w_L​=100×0.1
=10Ω
⇒i_o​=E_o/XL​=100/10​=10A
⇒i=i_o​sin(100t− π/2​)
⇒i=−i_o​sin[(π/2)​−100]
So we get
⇒i=−10cos(100t)A
therefore, option D is correct.

The line integral of the magnetic field of induction  around any closed path in free space is equal to absolute permeability of free space μ₀ times the total current flowing through area bounded by the path.
Ampere's circuital law is given by: 

From Ampere circuital law

The direction of field at the given point will be vertical up determined by the screw rule or right hand rule.

I = 40A
r = 15 cm = 15 x 10^-2 m
∴  = 5.34 x 10^-5 T

The magnetic field from the centre of wire of radius R is given by
B = ((μ₀I)/(2R²))r (r < R) ⇒ B ∝ r
and B = μ₀I/2πr (r > R) ⇒ B ∝ 1/r
From this descriptions, we can say that the graph (b) is a correct representation.