Magnetism & EMI
Q. In which of the following scenarios is the magnetic force on a charged particle zero?
A.
When the particle is at rest
B.
When the particle moves parallel to the magnetic field
C.
When the particle moves perpendicular to the magnetic field
D.
Both 1 and 2
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Solution
The magnetic force on a charged particle is zero when it is at rest or when it moves parallel to the magnetic field.
Correct Answer: D — Both 1 and 2
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Q. In which of the following scenarios will a charged particle experience no magnetic force?
A.
When moving parallel to the magnetic field
B.
When moving perpendicular to the magnetic field
C.
When at rest
D.
Both A and C
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Solution
A charged particle experiences no magnetic force when it is either at rest or moving parallel to the magnetic field.
Correct Answer: D — Both A and C
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Q. In which of the following scenarios will a charged particle experience the maximum magnetic force?
A.
When moving parallel to the magnetic field
B.
When moving perpendicular to the magnetic field
C.
When at rest
D.
When moving at an angle of 45 degrees
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Solution
A charged particle experiences maximum magnetic force when moving perpendicular to the magnetic field, as sin(90°) = 1.
Correct Answer: B — When moving perpendicular to the magnetic field
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Q. In which of the following scenarios will a charged particle not experience any magnetic force?
A.
When moving parallel to the magnetic field
B.
When moving perpendicular to the magnetic field
C.
When at rest
D.
Both a and c
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Solution
A charged particle will not experience any magnetic force when it is at rest or moving parallel to the magnetic field.
Correct Answer: D — Both a and c
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Q. In which of the following scenarios will a magnetic field be produced?
A.
A stationary charge
B.
A moving charge
C.
A neutral atom
D.
A charged particle at rest
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Solution
A magnetic field is produced by a moving charge. A stationary charge does not produce a magnetic field.
Correct Answer: B — A moving charge
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Q. Lenz's law states that the direction of induced current is such that it opposes what?
A.
The change in magnetic flux
B.
The flow of electric current
C.
The resistance in the circuit
D.
The applied voltage
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Solution
Lenz's law states that the direction of induced current will oppose the change in magnetic flux that produced it.
Correct Answer: A — The change in magnetic flux
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Q. The magnetic field inside a long solenoid is?
A.
Zero
B.
Uniform
C.
Non-uniform
D.
Depends on the current
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Solution
The magnetic field inside a long solenoid is uniform and parallel to the axis of the solenoid.
Correct Answer: B — Uniform
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Q. The power factor of an AC circuit is defined as the ratio of:
A.
Real power to apparent power
B.
Apparent power to real power
C.
Voltage to current
D.
Current to voltage
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Solution
The power factor is defined as the ratio of real power to apparent power.
Correct Answer: A — Real power to apparent power
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Q. The right-hand rule is used to determine the direction of?
A.
Magnetic field
B.
Current
C.
Force
D.
All of the above
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Solution
The right-hand rule can be used to determine the direction of the magnetic field, current, and force in electromagnetic situations.
Correct Answer: D — All of the above
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Q. Two parallel wires carry currents in the same direction. What is the nature of the force between them?
A.
Attractive
B.
Repulsive
C.
No force
D.
Depends on the current
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Solution
When two parallel wires carry currents in the same direction, they exert an attractive force on each other due to the magnetic fields they create.
Correct Answer: A — Attractive
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Q. Two parallel wires carry currents I₁ and I₂ in the same direction. What is the nature of the force between them?
A.
Attractive
B.
Repulsive
C.
Zero
D.
Depends on distance
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Solution
Parallel currents attract each other due to the magnetic fields they create.
Correct Answer: A — Attractive
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Q. Two parallel wires carrying currents I₁ and I₂ in the same direction are separated by a distance d. What is the force per unit length between them?
A.
(μ₀I₁I₂)/(2πd)
B.
(μ₀I₁I₂)/(4πd)
C.
(μ₀I₁I₂)/(8πd)
D.
(μ₀I₁I₂)/(πd)
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Solution
The force per unit length between two parallel wires is given by F/L = (μ₀I₁I₂)/(2πd).
Correct Answer: A — (μ₀I₁I₂)/(2πd)
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Q. Using Biot-Savart Law, what is the direction of the magnetic field produced by a current flowing in a straight wire?
A.
Radially inward
B.
Radially outward
C.
Perpendicular to the wire
D.
Parallel to the wire
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Solution
According to the right-hand rule, the magnetic field produced by a straight current-carrying wire is perpendicular to the wire.
Correct Answer: C — Perpendicular to the wire
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Q. Using Biot-Savart Law, what is the magnetic field at the center of a circular loop of radius R carrying current I?
A.
μ₀I/(2R)
B.
μ₀I/(4R)
C.
μ₀I/(πR)
D.
μ₀I/(2πR)
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Solution
The magnetic field at the center of a circular loop of radius R carrying current I is given by B = μ₀I/(2R) and for a complete loop, it simplifies to B = μ₀I/(2πR).
Correct Answer: D — μ₀I/(2πR)
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Q. What does Ampere's Law relate to in electromagnetism?
A.
Electric field and charge
B.
Magnetic field and current
C.
Electric potential and capacitance
D.
Magnetic flux and resistance
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Solution
Ampere's Law states that the magnetic field around a closed loop is proportional to the electric current passing through the loop.
Correct Answer: B — Magnetic field and current
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Q. What does the Biot-Savart Law describe?
A.
The force between two charges
B.
The magnetic field generated by a steady current
C.
The electric field due to a point charge
D.
The potential energy of a system of charges
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Solution
The Biot-Savart Law describes the magnetic field generated by a steady current flowing through a conductor.
Correct Answer: B — The magnetic field generated by a steady current
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Q. What happens to the induced current in a closed loop if the magnetic field through the loop is increasing?
A.
The induced current flows in a direction to oppose the increase
B.
The induced current flows in the same direction as the increase
C.
The induced current becomes zero
D.
The induced current fluctuates
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Solution
According to Lenz's law, the induced current will flow in a direction that opposes the increase in magnetic flux.
Correct Answer: A — The induced current flows in a direction to oppose the increase
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Q. What happens to the induced current in a coil if the magnetic field is suddenly removed?
A.
Induced current continues to flow
B.
Induced current stops immediately
C.
Induced current increases
D.
Induced current decreases gradually
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Solution
If the magnetic field is suddenly removed, the change in magnetic flux becomes zero, and thus the induced current stops immediately.
Correct Answer: B — Induced current stops immediately
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Q. What happens to the induced current when the magnetic field is removed from a closed loop?
A.
It continues to flow indefinitely
B.
It stops immediately
C.
It flows in the opposite direction
D.
It decreases gradually
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Solution
When the magnetic field is removed from a closed loop, the induced current stops immediately as there is no longer a changing magnetic flux.
Correct Answer: B — It stops immediately
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Q. What happens to the induced current when the magnetic field through a loop is increased?
A.
The induced current flows in a direction to oppose the increase
B.
The induced current flows in the same direction as the increase
C.
The induced current becomes zero
D.
The induced current fluctuates
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Solution
According to Lenz's law, the induced current will flow in a direction that opposes the increase in magnetic flux.
Correct Answer: A — The induced current flows in a direction to oppose the increase
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Q. What happens to the induced EMF if the area of the coil is increased while the magnetic field strength remains constant?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
Increasing the area of the coil while keeping the magnetic field strength constant increases the magnetic flux through the coil, which according to Faraday's law increases the induced EMF.
Correct Answer: A — It increases
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Q. What happens to the induced EMF if the area of the loop in a uniform magnetic field is doubled while keeping the magnetic field constant?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
If the area of the loop is doubled, the induced EMF will also double, as it is directly proportional to the area.
Correct Answer: A — It doubles
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Q. What happens to the induced EMF if the rate of change of magnetic flux is doubled?
A.
It remains the same
B.
It doubles
C.
It halves
D.
It quadruples
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Solution
According to Faraday's law, the induced EMF is directly proportional to the rate of change of magnetic flux. Therefore, if the rate is doubled, the induced EMF also doubles.
Correct Answer: B — It doubles
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Q. What happens to the induced EMF if the speed of a conductor moving through a magnetic field is doubled?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
If the speed of the conductor is doubled, the rate of change of magnetic flux increases, thus the induced EMF also doubles.
Correct Answer: A — It doubles
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Q. What happens to the induced EMF when the area of a loop in a changing magnetic field is increased?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
According to Faraday's law, if the area of the loop is increased in a changing magnetic field, the induced EMF increases.
Correct Answer: A — Increases
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Q. What happens to the induced EMF when the area of a loop in a magnetic field is increased?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on the field strength
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Solution
According to Faraday's law, if the area of the loop is increased in a magnetic field, the induced EMF increases.
Correct Answer: A — Increases
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Q. What happens to the magnetic field inside a long solenoid when the current through it is increased?
A.
Magnetic field decreases
B.
Magnetic field remains constant
C.
Magnetic field increases
D.
Magnetic field becomes zero
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Solution
The magnetic field inside a long solenoid is directly proportional to the current flowing through it. Increasing the current increases the magnetic field strength.
Correct Answer: C — Magnetic field increases
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Q. What happens to the magnetic field inside a solenoid if the current is reversed?
A.
Reverses direction
B.
Increases
C.
Decreases
D.
Remains the same
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Solution
Reversing the current reverses the direction of the magnetic field.
Correct Answer: A — Reverses direction
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Q. What happens to the magnetic field inside a solenoid when the current flowing through it is increased?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
The magnetic field inside a solenoid is directly proportional to the current flowing through it; thus, it increases with an increase in current.
Correct Answer: A — Increases
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Q. What happens to the magnetic field inside a solenoid when the current through it is increased?
A.
It decreases
B.
It remains constant
C.
It increases
D.
It becomes zero
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Solution
The magnetic field inside a solenoid is directly proportional to the current flowing through it, so increasing the current increases the magnetic field.
Correct Answer: C — It increases
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