This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Generation of an Alternating EMF”.
1. Which, among the following, is the correct expression for alternating emf generated?
a) e=2Blvsin(θ)
b) e=2B2lvsin(θ)
c) e=Blvsin(θ)
d) e=4Blvsin(θ)
View Answer
Explanation: The correct expression for alternating emf generated is e=Blvsin(θ). Where B stands for magnetic field density, l is the length of each of the parallel sides v is the velocity with which the conductor is moved and θ is the angle between the velocity and the length.
2. What should theta be in order to get maximum emf?
a) 00
b) 900
c) 1800
d) 450
View Answer
Explanation: The value of θ should be 900 in order to get maximum emf because e = Blvsin(θ) and sin is maximum when θ is 900.
3. Calculate the maximum emf when the velocity is 10m/s, the length is 3m and the magnetic field density is 5T.
a) 150V
b) 100V
c) 300V
d) 0V
View Answer
Explanation: We know that: emax=Bvl
Substituting the values from the given question, we get e=150V.
4. When a coil is rotated in a magnetic field, the emf induced in it?
a) Is maximum
b) Is minimum
c) Continuously varies
d) Remains constant
View Answer
Explanation: When a coil is rotated in a magnetic field, cross sectional area varies due to which the number of flux lines crossing it varies, which causes the emf to vary continuously.
5. emf is zero if the angle between velocity and length is _____
a) 00
b) 900
c) 2700
d) 450
View Answer
Explanation: If the angle between velocity and length is zero, sinθ=0
So, e=Bvlsinθ = 0.
6. In an A.C. generator, increase in number of turns in the coil _________
a) Increases emf
b) Decreases emf
c) Makes the emf zero
d) Maintains the emf at a constant value
View Answer
Explanation: In an A.C. generator, the emf increases as the number of turns in the coil increases because the emf is directly proportional to the number of turns.
7. The number of cycles that occur in one second is termed as ___________
a) Waveform
b) Frequency
c) Amplitude
d) Period
View Answer
Explanation: The number of cycles that occur in one second is known as the frequency. It is the reciprocal of the time period.
Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.
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