Q. According to Faraday's law, the induced electromotive force (emf) in a closed loop is proportional to what?
A.
The area of the loop
B.
The rate of change of magnetic flux
C.
The resistance of the loop
D.
The current in the loop
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Solution
Faraday's law states that the induced emf is proportional to the rate of change of magnetic flux through the loop.
Correct Answer:
B
— The rate of change of magnetic flux
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Q. If a conductor moves perpendicular to a magnetic field, what is the induced emf proportional to?
A.
Speed of the conductor
B.
Angle of movement
C.
Length of the conductor
D.
Both speed and length
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Solution
The induced emf is proportional to both the speed of the conductor and the length of the conductor when moving perpendicular to the magnetic field.
Correct Answer:
D
— Both speed and length
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Q. If the magnetic field strength is doubled, what happens to the induced emf in a loop moving through the field?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
If the magnetic field strength is doubled, the induced emf also doubles, as it is directly proportional to the magnetic field strength.
Correct Answer:
A
— It doubles
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Q. If the magnetic field through a loop of wire is increasing, what is the direction of the induced current?
A.
Clockwise
B.
Counterclockwise
C.
No current induced
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 be counterclockwise.
Correct Answer:
B
— Counterclockwise
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Q. In electromagnetic induction, what does the term 'flux linkage' refer to?
A.
The product of magnetic field and area
B.
The total magnetic flux through a coil
C.
The induced emf in a circuit
D.
The resistance of the coil
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Solution
Flux linkage refers to the total magnetic flux through a coil, which is the product of the magnetic flux and the number of turns in the coil.
Correct Answer:
B
— The total magnetic flux through a coil
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Q. What happens to the induced current if the magnetic field is removed?
A.
It increases
B.
It decreases
C.
It reverses direction
D.
It stops
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Solution
If the magnetic field is removed, the induced current stops because there is no longer a change in magnetic flux.
Correct Answer:
D
— It stops
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Q. What is the effect of increasing the area of a loop in a uniform magnetic field on the induced emf?
A.
Induced emf increases
B.
Induced emf decreases
C.
Induced emf remains the same
D.
Induced emf becomes zero
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Solution
The induced emf depends on the rate of change of magnetic flux, not directly on the area of the loop in a uniform magnetic field. Therefore, it remains the same if the magnetic field is constant.
Correct Answer:
C
— Induced emf remains the same
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Q. What is the formula for the induced electromotive force (emf) in a coil when the magnetic flux changes?
A.
emf = -dΦ/dt
B.
emf = F/q
C.
emf = W/t
D.
emf = mv^2/r
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Solution
The induced emf in a coil is given by Faraday's law of electromagnetic induction, which states that emf = -dΦ/dt, where Φ is the magnetic flux.
Correct Answer:
A
— emf = -dΦ/dt
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Q. What is the principle behind a transformer?
A.
Conservation of energy
B.
Electromagnetic induction
C.
Ohm's law
D.
Newton's laws
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Solution
The principle behind a transformer is electromagnetic induction, where a changing magnetic field induces an emf in a secondary coil.
Correct Answer:
B
— Electromagnetic induction
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Q. What is the relationship between induced emf and the resistance of the circuit?
A.
Induced emf is independent of resistance
B.
Higher resistance leads to higher induced emf
C.
Lower resistance leads to higher induced emf
D.
Induced emf is inversely proportional to resistance
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Solution
Induced emf is independent of the resistance of the circuit; however, the current produced will be affected by the resistance according to Ohm's law.
Correct Answer:
A
— Induced emf is independent of resistance
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Q. Which law states that the direction of induced current is such that it opposes the change in magnetic flux?
A.
Faraday's law
B.
Lenz's law
C.
Newton's first law
D.
Ampere's law
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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.
Correct Answer:
B
— Lenz's law
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Q. Which of the following factors does NOT affect the induced emf in a coil?
A.
Number of turns in the coil
B.
Rate of change of magnetic flux
C.
Resistance of the wire
D.
Strength of the magnetic field
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Solution
The induced emf is affected by the number of turns in the coil, the rate of change of magnetic flux, and the strength of the magnetic field. The resistance of the wire does not affect the induced emf directly.
Correct Answer:
C
— Resistance of the wire
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