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=d(phi)/dt

b) e=dt/d(phi)

c) e=t*phi

d) e=t^{2}phi

View Answer

Explanation: The formula foe induced emf is e=d(phi)/dt because the induced emf is the flux linkage per unit time.

2. The formula for induced emf is _______

a) emf=B^{2}l

b) emf=Bil

c) emf=Blv

d) emf=B^{2}v

View Answer

Explanation: The formula for induced emf is: emf=Blv, where B is the magnetic field, l is the length of the conductor and v is the velocity with which it is moving in the magnetic field.

3. If a conductor 0.2m long moves with a velocity of 0.3m/s in a magnetic field of 5T, calculate the emf induced.

a) 0.3V

b) 0.03V

c) 30V

d) 3V

View Answer

Explanation: The formula for induced emf is: emf=Blv. Substituting the values of B, l and v from the question, we get emf=0.3V.

4. Find the length of a conductor which is moving with a velocity 0.4m/s in a magnetic field of 8T, inducing an emf of 20V.

a) 50m

b) 5m

c) 6.25m

d) 0.5m

View Answer

Explanation: The formula for induced emf is: emf=Blv. Substituting the values of B, emf and v from the question, we get l=6.25m.

5. Find the strength of magnetic field in a conductor 0.5m long moving with a velocity of 10m/s, inducing an emf of 20V.

a) 1T

b) 2T

c) 3T

d) 4T

View Answer

Explanation: The formula for induced emf is: emf=Blv. Substituting the values of l, emf and v from the question, we get B=4T.

6. What is emf?

a) Force

b) Voltage

c) Current

d) Flux

View Answer

Explanation: Electromotive force is not actually a force. It is basically a voltage. It is the voltage developed by any source of electrical energy.

7. An E.M.F. can be induced by _________

a) Change in magnetic field

b) Change in the area of cross section

c) Change in angle between magnetic field and area

d) Change in magnetic field, area and angle

View Answer

Explanation: The dot product of magnetic field vector and area vector.

emf=BAcos(theta), hence if either of the three, that is, magnetic field, area or angle changes, thee emf will change.

8. The emf induced in a coil having N turns is?

a) e=phi/t

b) e=N*phi/t

c) e=N*phi*t

d) e=N^{2}*phi*t

View Answer

Explanation: The emf induced in a coil having N turns is, e=N*phi/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*phi/t.

9. 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

View Answer

Explanation: The number of magnetic flux lines per unit area is the magnetic flux, because flux is the number of field lines per unit area.

10. What is the consequence of motor effect?

a) Current

b) Voltage

c) Electromagnetic induction

d) EMF

View Answer

Explanation: Motor effect is when a current carrying conductor in a magnetic field experiences a force, hence its consequence is electromagnetic induction.

**Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.**

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