This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Electromagnetic Induction”.
1. An E.M.F. can be induced by _________
a) Change in the magnetic field
b) Change in the area of cross section
c) Change in angle between magnetic field and area
d) Change in the magnetic field, area and angle
Explanation: It is 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, the emf will change.
2. What happens to the current in a coil while accelerating a magnet inside it?
c) Remains constant
Explanation: A change in the magnetic field induces an emf. When there is an emf, there has to be a current. Hence, when the magnet is moved inside a coil, the current in it increases.
3. What is the consequence of motor effect?
c) Electromagnetic induction
Explanation: Motor effect is when a current carrying conductor in a magnetic field experiences a force, hence its consequence is electromagnetic induction.
4. The total number of magnetic field lines passing through an area is termed as?
c) Magnetic flux
d) Magnetic flux density
Explanation: The number of magnetic flux lines per unit area is the magnetic flux, because the flux is the number of field lines per unit area.
5. The formula for induced emf is __________
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.
6. If a conductor 0.2m long moves with a velocity of 0.3m/s in a magnetic field of 5T, calculate the emf induced.
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.
7. 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.
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.
8. 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.
Explanation: The formula for induced emf is: emf=Blv. Substituting the values of l, emf and v from the question, we get B=4T.
9. What does emf stand for?
a) Electronic magnetic force
b) Electromotive force
c) Electromagnetic force
d) Electromated force
Explanation: emf stands for electromotive force. It is the voltage developed by any source of electrical energy.
10. What is emf?
Explanation: Electromotive force is not actually a force. It is basically a voltage. It is the voltage developed by any source of electrical energy.
Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.
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