Physics: Topic-wise Test- 8 - NEET MCQ

E = F/q = KQ/r²

Properties of Electric Field Lines. At every point on an electric field line, the tangent represents the direction of electric field. If two field lines cross each other at the point, then there would be two possible directions for electric field which is physically impossible.

Electric Field Intensity E = F\q

E = F/q

Conventionally, field lines originate from a positive point charge and terminate at negative charge

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.

Correct answer is A.

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.

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.

To find the characteristic temperature using Wien's displacement law, we start with the formula λ_m T = 0.29 cmK. We need to convert the wavelength λ_m from meters to centimeters: λ_m = 5×10^-7 m = 5×10^-5 cm. Substitute this into the formula: T = 0.29 cmK / 5×10^-5 cm, which gives T = 5800 K. Due to rounding and context of black body radiation, this temperature is closer to 6000 K. Thus, the characteristic temperature range is approximately 6000 K.

X-rays are absorbed by the atmosphere and therefore the source of X-rays must lie outside the atmosphere to carry out X-ray astronomy and therefore satellites orbiting the earth are necessary but radio waves and visible light can penetrate through the atmosphere and therefore optical and radio telescopes can be built on the ground.

E is the electric field vector, and B is the magnetic field vector of the EM wave. For electromagnetic waves E and B are always perpendicular to each other and perpendicular to the direction of propagation. Electromagnetic waves are transverse waves. The wave number is k = 2π/λ, where λ is the wavelength of the wave.

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.

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.

n₁=10 turns per cm, =1000 turns per metre
n₂l=100, A=10 c=0.1 m², M=μ₀n₁(n₂l) A
=4πx10^-7×1000×100×0.1H=0.13mh

The total inductance of inductors connected in series is given by the following formula:
L_eq = L₁ + L₂
Substituting the values in the equation, we get the total inductance as
L_eq = L + L = 2L
Hence, the total inductance of two inductors connected in series is 2L.

The magnetic field through the secondary of N2 turns of each other of area S is given as,
N2= Φ2=N2(BS)
     =μ₀n₁N₂i₁S
M= N₂Φ₂/i1
M= μ₀n₁N₂S
Substituting the values.
M=(4πx10^-7) x100x200x5x10^-3
   =1287142.86x10^-10
   =12.57x10^-5H

As φ =mi
now take change in flux
dφ/dt=d(mi)/dt
we can write it as
dφ/ dt= m Δi/Δt
-e=m(2-5)/0.03
e=3m/0.03
1000=300m/3
m=10