In a circuit, the current falls from 14 A to 4 A in a time 0.2 ms. If the induced emf is 150 V, then the self-inductance of the circuit is:
1
H
2
mH
3
mH
4
H
Official Solution
Correct Option: (3)
Step 1: Use the Self -Inductance Formula The induced emf is given by: where: - V, - A, - ms = s. Step 2: Solve for
02
PYQ 2024
medium
physicsID: ap-eamce
The domain in ferromagnetic material is in the form of a cube of side 2 mum. Number of atoms in that domain is and each atom has a dipole movement of . The magnetisation of the domain is (approximately).
1
2
3
4
Official Solution
Correct Option: (1)
Magnetisation is defined as: Total dipole moment is: The volume of the domain is: Thus, the magnetisation is:
03
PYQ 2024
medium
physicsID: ap-eamce
If the current through an inductor increases from 2 A to 3 A, the magnetic energy stored in the inductor increases by
1
125%
2
225%
3
50%
4
75%
Official Solution
Correct Option: (1)
The energy stored in an inductor is given by: Initial energy: Final energy: Percentage increase: Thus, the correct answer is 125\%.
04
PYQ 2024
easy
physicsID: ap-eamce
Magnetic field at a distance from z axis is present in the region. is constant and is time. The magnitude of induced electric field at a distance from z-axis is.
1
2
3
4
Official Solution
Correct Option: (4)
The magnetic field at a distance from the z-axis is given by . According to Faraday's law of induction, the induced electric field is related to the rate of change of magnetic flux. The induced electric field is given by: Where is the magnetic flux. Since , we get: Thus, the induced electric field at a distance from the z-axis is .
05
PYQ 2024
medium
physicsID: ap-eamce
A metallic wire loop of side m and resistance of is moved with a constant velocity in a uniform magnetic field of as shown in the figure. The magnetic field is perpendicular to the plane of the loop. The loop is connected to a network of resistors. The velocity of loop so as to have a steady current of mA in loop is:
1
cm s
2
cm s
3
cm s
4
cm s
Official Solution
Correct Option: (2)
Step 1: Understanding Electromagnetic Induction From Faraday's Law of electromagnetic induction, the induced emf ( ) in the loop is given by: where: - (magnetic field strength), - (side length of the loop), - (velocity of the loop, to be determined).
Step 2: Applying Ohm's Law The induced current in the loop is given by: where: - (resistance of the loop), - A (steady current in the loop).
Step 3: Solving for Substituting the values:
06
PYQ 2024
easy
physicsID: ap-eamce
An electron is moving with a velocity m/s in an electric field V/m and a magnetic field T. The magnitude and direction (with x-axis) of the Lorentz force acting on the electron is
1
2
3
4
Official Solution
Correct Option: (3)
The Lorentz force is given by: Computing the cross product : Solving for , we get: The direction is given by: Thus, the correct answer is .
07
PYQ 2024
medium
physicsID: ap-eamce
A magnet suspended in a uniform magnetic field is heated so as to reduce its magnetic moment by 19%. By doing this, the time period of the magnet approximately
1
Increases by 11%
2
Decreases by 19%
3
Increases by 19%
4
Decreases by 4%
Official Solution
Correct Option: (1)
The time period of a magnet in a magnetic field is given by: When decreases by 19%, let : Thus, the time period increases by 11%.
08
PYQ 2024
medium
physicsID: ap-eamce
The Solar Radiation is
1
Stationary wave
2
Mechanical wave
3
Transverse EM wave
4
Longitudinal EM wave
Official Solution
Correct Option: (3)
Solar radiation is composed of electromagnetic (EM) waves. EM waves are transverse waves where the electric and magnetic fields oscillate perpendicular to the direction of wave propagation. Since solar radiation is an EM wave, and EM waves are transverse in nature, the correct answer is: Transverse EM wave
09
PYQ 2024
easy
physicsID: ap-eamce
An electromagnetic wave travels in a medium with a speed of . The relative permeability of the medium is 1. Then the relative permittivity is.
1
1.75
2
2
3
2.25
4
2.75
Official Solution
Correct Option: (3)
The speed of light in a medium is given by: Where:
- is the speed of the electromagnetic wave in the medium
- is the speed of light in a vacuum
- is the relative permeability of the medium
- is the relative permittivity of the medium Given that and , and , we can solve for : Thus, the relative permittivity is .
