# Basic Electrical Engineering Questions and Answers – Magnitude of the Generated or Induced EMF

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This set of Basic Electrical Engineering test focuses on “Magnitude of the Generated or Induced EMF”.

1. Which, among the following, is the formula for induced emf?
a) e=dϕ /dt
b) e=dt/dϕ
c) e=t*ϕ
d) e=t2ϕ

Explanation: The formula for induced emf is e = dϕ /dt because the induced emf is the flux linkage per unit time.

2. According to _________________ induced emf is equal to rate of change of magnetic flux.
a) Newton’s law
b) Lenz law
d) Coulomb’s law

Explanation: According to Faraday law of electromagnetic induction, induced emf is equal to rate of change of magnetic flux.

3. The emf induced in a coil having N turns is?
a) e=ϕ/t
b) e=N*ϕ/t
c) e=N*ϕ*t
d) e=N2*ϕ*t

Explanation: The emf induced in a coil having N turns is, e=N*ϕ/t. This is because, the emf in a single coil is the flux linkage per unit time, that is, phi/t. Hence the flux induced in N turns is N*ϕ/t.
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4. According to ____________________ induced emf oppose the cause due to which they are produced.
a) Newton’s law
b) Lenz law
d) Coulomb’s law

Explanation: According to Lenz law, emf is induced in such a way that it opposes the cause due to which it is produced.

5. North pole induces __________
a) Clockwise current
b) Anti-clockwise current
c) Zero current
d) Infinite current

Explanation: A north pole will always induce an anti-clockwise current whereas a south pole will always induce a clockwise current due to electromagnetic theory.

6. What is the principle of the transformer?
a) Gauss law
b) Coulomb’s law
c) Electromagnetic induction
d) Ampere’s law

Explanation: In transformer, flux in secondary coil change due to current in the primary coil and hence current get induced in secondary coil.

7. Voltage induced in secondary coil of transformer is given by__________________
a) NP*VP/NS
b) NS*VP/NP
c) (NP/VP)*NS
d) NP/(VP*NS)

Explanation: In transformer, VP/VS = NP/NS
So, VS = NS*VP/NP.

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