Electromagnetic Induction
Q. If the area of a loop in a magnetic field is doubled while keeping the magnetic field strength constant, what happens to the magnetic flux?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Magnetic flux (Φ) is given by Φ = B * A. If the area (A) is doubled, the magnetic flux also doubles.
Correct Answer: A — It doubles
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Q. If the area of a loop is doubled while keeping the magnetic field constant, how does the magnetic flux change?
A.
It remains the same
B.
It doubles
C.
It triples
D.
It halves
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Solution
Magnetic flux Φ is given by Φ = B * A. If the area A is doubled while B remains constant, the magnetic flux also doubles.
Correct Answer: B — It doubles
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Q. If the area of a loop is doubled while the magnetic field remains constant, how does the induced EMF change?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
Induced EMF is proportional to the area of the loop. If the area is doubled, the induced EMF also doubles.
Correct Answer: A — Doubles
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Q. If the magnetic field through a loop is doubled while the area remains constant, what happens to the magnetic flux?
A.
Magnetic flux doubles
B.
Magnetic flux halves
C.
Magnetic flux remains the same
D.
Magnetic flux becomes zero
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Solution
Magnetic flux is given by the product of magnetic field strength and area. If the magnetic field is doubled, the magnetic flux also doubles.
Correct Answer: A — Magnetic flux doubles
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Q. If the magnetic field through a loop is increased uniformly, what happens to the induced current in the loop?
A.
It flows in the direction of the magnetic field
B.
It flows in the opposite direction to the magnetic field
C.
It remains constant
D.
It stops flowing
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Solution
According to Lenz's law, the induced current will flow in the opposite direction to oppose the increase in magnetic flux.
Correct Answer: B — It flows in the opposite direction to the magnetic field
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Q. If the magnetic field through a loop is increasing at a constant rate, what can be said about the induced current?
A.
It is constant
B.
It is increasing
C.
It is decreasing
D.
It is zero
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Solution
If the magnetic field is increasing at a constant rate, the induced EMF is also increasing, which means the induced current is increasing.
Correct Answer: B — It is increasing
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Q. If the rate of change of current in an inductor is 2 A/s, what is the induced EMF if the inductance is 3 H?
A.
6 V
B.
3 V
C.
2 V
D.
1 V
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Solution
Induced EMF (ε) = -L(dI/dt) = -3 H * 2 A/s = -6 V.
Correct Answer: A — 6 V
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Q. If the resistance of a circuit is 10 ohms and the induced EMF is 20 V, what is the induced current?
A.
2 A
B.
0.5 A
C.
10 A
D.
5 A
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Solution
Using Ohm's law, I = V/R. Here, I = 20 V / 10 Ω = 2 A.
Correct Answer: A — 2 A
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Q. If the resistance of a circuit is doubled while keeping the induced EMF constant, what happens to the induced current?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's law (I = V/R), if the resistance is doubled while the voltage (induced EMF) remains constant, the current will be halved.
Correct Answer: B — It halves
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Q. In a generator, if the speed of rotation is doubled, what happens to the induced EMF?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
The induced EMF in a generator is directly proportional to the speed of rotation. Therefore, if the speed is doubled, the induced EMF also doubles.
Correct Answer: A — It doubles
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Q. In a generator, mechanical energy is converted into electrical energy through the principle of:
A.
Electrostatics
B.
Electromagnetic induction
C.
Thermodynamics
D.
Optics
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Solution
In a generator, mechanical energy is converted into electrical energy through the principle of electromagnetic induction, as the motion of conductors in a magnetic field induces an EMF.
Correct Answer: B — Electromagnetic induction
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Q. In a generator, mechanical energy is converted into electrical energy through which principle?
A.
Electromagnetic induction
B.
Thermal conduction
C.
Photoelectric effect
D.
Capacitance
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Solution
In a generator, mechanical energy is converted into electrical energy through the principle of electromagnetic induction.
Correct Answer: A — Electromagnetic induction
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Q. In a generator, mechanical energy is converted into electrical energy through which process?
A.
Electromagnetic induction
B.
Thermal conduction
C.
Photoelectric effect
D.
Electrolysis
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Solution
In a generator, mechanical energy is converted into electrical energy through the process of electromagnetic induction.
Correct Answer: A — Electromagnetic induction
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Q. In a generator, what is the role of the rotating coil in a magnetic field?
A.
To create a magnetic field
B.
To induce current
C.
To store energy
D.
To measure voltage
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Solution
In a generator, the rotating coil in a magnetic field induces current through electromagnetic induction, converting mechanical energy into electrical energy.
Correct Answer: B — To induce current
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Q. In a transformer, if the primary coil has 200 turns and the secondary coil has 50 turns, what is the relationship between the primary and secondary voltages?
A.
Vp/Vs = 4
B.
Vp/Vs = 0.25
C.
Vp/Vs = 2
D.
Vp/Vs = 1
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Solution
The voltage ratio in a transformer is inversely proportional to the turns ratio: Vp/Vs = Np/Ns = 200/50 = 4.
Correct Answer: A — Vp/Vs = 4
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Q. In a transformer, if the primary coil has 200 turns and the secondary coil has 50 turns, what is the turns ratio?
A.
4:1
B.
1:4
C.
2:1
D.
1:2
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Solution
Turns ratio = Np/Ns = 200/50 = 4:1.
Correct Answer: B — 1:4
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Q. In a transformer, the ratio of the number of turns in the primary coil to the secondary coil determines what?
A.
The voltage transformation ratio
B.
The current transformation ratio
C.
The power transformation ratio
D.
The frequency of the output
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Solution
The voltage transformation ratio in a transformer is determined by the ratio of the number of turns in the primary coil to that in the secondary coil.
Correct Answer: A — The voltage transformation ratio
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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. 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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A.
The direction of induced current opposes the change in magnetic flux
B.
The induced current flows in the same direction as the change in magnetic flux
C.
The induced EMF is always positive
D.
The magnetic field is always perpendicular to the current
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Solution
Lenz's law states that the direction of induced current is such that it opposes the change in magnetic flux that produced it.
Correct Answer: A — The direction of induced current opposes the change in magnetic flux
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Q. What is self-inductance?
A.
The ability of a coil to induce EMF in itself
B.
The ability of a coil to induce EMF in another coil
C.
The resistance of a coil to current flow
D.
The capacitance of a coil
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Solution
Self-inductance is the property of a coil to induce an EMF in itself due to a change in current.
Correct Answer: A — The ability of a coil to induce EMF in itself
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Q. What is self-induction?
A.
Induction of EMF in a coil due to its own changing current
B.
Induction of EMF in a coil due to an external magnetic field
C.
Induction of current in a conductor due to a magnetic field
D.
Induction of voltage in a capacitor
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Solution
Self-induction is the phenomenon where a changing current in a coil induces an EMF in the same coil.
Correct Answer: A — Induction of EMF in a coil due to its own changing current
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Q. What is the direction of the induced current when the magnetic field through a loop is increasing?
A.
Clockwise
B.
Counterclockwise
C.
No current
D.
Depends on the field strength
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Solution
According to Lenz's law, the induced current will flow in a direction that opposes the change in magnetic flux. If the magnetic field is increasing, the induced current will flow counterclockwise.
Correct Answer: B — Counterclockwise
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