A. Current
B. Voltage
C. Electromagnetic induction
D. EMF
Answer: C
The motor effect is when a current-carrying conductor in a magnetic field experiences a force, hence its consequence is electromagnetic induction.
22. The total number of magnetic field lines passing through an area is termed as?
A. Voltage
B. EMF
C. Magnetic flux
D. Magnetic flux density
Answer: C
The number of magnetic field lines passing through an area is magnetic flux.
Magnetic flux: The number of magnetic field lines passing through a surface area normally is called magnetic flux. It is denoted by ϕ.
Magnetic flux is mathematically equal to the dot product of the magnetic field and area vector through which it is passing.
23. The formula for induced emf if magnetic field, length, and velocity of conductor all are mutually perpendicular is __________
A. emf = B2l
B. emf = Bil
C. emf = Blv
D. emf = B2v
Answer: C
The formula for induced emf is emf = Blv,
where
B is the magnetic field,
l is the length of the conductor
v is the velocity with which it is moving in the magnetic field and all three quantities are mutually perpendicular to each other.
24. If a conductor 0.2m long moves with a velocity of 0.3m/s in a magnetic field of 5T, calculate the emf induced if the magnetic field, velocity, and length of the conductor are mutually perpendicular to each other.
A. 0.3V
B. 0.03V
C. 30V
D. 3V
Answer: A
The formula for induced emf is
emf = Blv
if B,l, and v are perpendicular to each other. Substituting the values of B, l, and v from the question, we get emf = 0.3V.
25. Find the length of a conductor which is moving with a velocity of 0.4m/s in a magnetic field of 8T, inducing an emf of 20V if the magnetic field, velocity, and length of the conductor are mutually perpendicular to each other.
A. 50m
B. 5m
C. 6.25m
D. 0.5m
Answer: C
The formula for induced emf is
emf = Blv if B, l, and v are perpendicular to each other.
Substituting the values of B, emf, and v from the question, we get l = 6.25m.
26. Find the strength of the magnetic field in a conductor 0.5m long moving with a velocity of 10m/s, inducing an emf of 20V if the magnetic field, velocity, and length of the conductor are mutually perpendicular to each other.
A. 1T
B. 2T
C. 3T
D. 4T
Answer: D
The formula for induced emf is
emf = Blv if B, l, and v are perpendicular to each other.
Substituting the values of l, emf, and v from the question, we get B = 4T.
27. What does emf stand for?
A. Electronic magnetic force
B. Electromotive force
C. Electromagnetic force
D. Electromated force
Answer: B
Emf stands for electromotive force. It is the voltage developed by any source of electrical energy.
28. What is emf (Electromagnetic Force)?
A. Force
B. Voltage
C. Current
D. Flux
Answer: B
Electromotive force is not actually a force. It is basically a voltage. It is the voltage developed by any source of electrical energy.
29. According to Faraday’s laws of electromagnetic induction, an emf is induced in a conductor whenever?
A. The conductor is perpendicular to the magnetic field
B. Lies in the magnetic field
C. Cuts magnetic lines of flux
D. Moves parallel to the magnetic field
Answer: C
An emf is induced, according to Faraday’s laws of electromagnetic induction, whenever the conductor in a magnetic field cuts the magnetic lines of flux.
30. Direction of induced emf is determined by __________
A. Fleming’s left-hand rule
B. Fleming’s right-hand rule
C. Faraday’s law
D. Right-hand thumb rule
Answer: B
Fleming’s left-hand rule stated that if the index finger points toward magnetic flux, the thumb toward the motion of the conductor, then the middle finger points toward the induced emf.
