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Electrical Breakdown
MCQ questions and answers.
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MCQ Questions
1. What is meant by electrical breakdown in an insulator?
A.
The insulator becomes a good conductor due to a strong electric field
B.
The insulator becomes colder in an electric field
C.
The insulator changes its shape permanently
D.
The insulator loses all its mass
Correct Answer:
The insulator becomes a good conductor due to a strong electric field
Explanation:
Electrical breakdown occurs when a sufficiently strong electric field provides enough energy for charge carriers to move through the insulator, causing a sudden increase in conductivity.
2. The minimum electric field required to cause breakdown in an insulator is called its:
A.
Critical temperature
B.
Breakdown field strength
C.
Electrical resistance
D.
Permittivity
Correct Answer:
Breakdown field strength
Explanation:
Breakdown field strength is the minimum electric field at which an insulator starts conducting significantly.
3. Before electrical breakdown, an ideal insulator has:
A.
Very high electrical resistance
B.
Zero electrical resistance
C.
Very high current flow
D.
A large number of free electrons
Correct Answer:
Very high electrical resistance
Explanation:
An insulator normally has very high resistance, so it allows only a negligible current to pass before breakdown.
4. What happens to the current through an insulator when electrical breakdown begins?
A.
It increases sharply
B.
It becomes exactly zero
C.
It remains unchanged in all conditions
D.
It reverses direction automatically
Correct Answer:
It increases sharply
Explanation:
During breakdown, many charge carriers become available, so the conductivity and current increase sharply.
5. Which condition is most likely to cause electrical breakdown in an insulating material?
A.
Applying a voltage below its breakdown voltage
B.
Applying a very high voltage across it
C.
Keeping it in complete darkness
D.
Reducing the number of electric charges near it
Correct Answer:
Applying a very high voltage across it
Explanation:
A very high voltage can produce an electric field greater than the material's breakdown field strength, leading to electrical breakdown.
6. The voltage at which an insulator starts conducting heavily is called:
A.
Breakdown voltage
B.
Thermal voltage
C.
Contact voltage
D.
Neutral voltage
Correct Answer:
Breakdown voltage
Explanation:
Breakdown voltage is the applied voltage at which the electric field in an insulating material becomes strong enough to initiate breakdown.
7. Electrical breakdown can permanently damage an insulator because it may cause:
A.
A conducting path through the material
B.
A complete absence of electric field
C.
A decrease in all charge motion
D.
The material to become a perfect vacuum
Correct Answer:
A conducting path through the material
Explanation:
A strong breakdown current can produce a permanent conducting path, especially when the material is heated or damaged.
8. Which property of an insulator is directly related to its resistance against electrical breakdown?
A.
Dielectric strength
B.
Density only
C.
Color only
D.
Surface brightness
Correct Answer:
Dielectric strength
Explanation:
Dielectric strength is the maximum electric field an insulating material can withstand without electrical breakdown.
9. If the applied electric field in an insulator is less than its breakdown field strength, the insulator generally:
A.
Continues to act as an insulator
B.
Immediately becomes a metal
C.
Produces a large current
D.
Explodes in every case
Correct Answer:
Continues to act as an insulator
Explanation:
An insulator remains highly resistive when the applied electric field is below its breakdown field strength.
10. In electrical breakdown, the main reason for the sudden rise in conductivity is the increase in:
A.
Free charge carriers
B.
Material color
C.
Mass of the insulator
D.
Distance between electrodes only
Correct Answer:
Free charge carriers
Explanation:
A strong electric field releases or accelerates charge carriers, increasing their number and causing the insulator to conduct heavily.
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Electrical Breakdown
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