11. The unit for dielectric strength is ____________
A. V/m2
B. MV/m2
C. MV/m
D. Vm
Answer: C
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and length, its unit is MV/m.
12. If the Voltage increases, what happens to dielectric strength?
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: A
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and length. Hence as potential increases, dielectric strength also increases.
13. If the potential difference in a material is 4MV and the thickness of the material is 2m, calculate the dielectric strength.
A. 2MV/m
B. 4MV/m
C. 6MV/m
D. 8MV/m
Answer: A
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and thickness.
Dielectric strength = V/t = 4/2 = 2MV/m.
14. If the dielectric strength of a material is 4MV/m and its potential difference is 28MV, calculate the thickness of the material.
A. 4m
B. 7m
C. 5m
D. 11m
Answer: B
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and thickness.
V/dielectric strength = t = 28/4 = 7m.
15. If the thickness of the material increases, what happens to the dielectric strength?
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: B
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and thickness. Hence as thickness increases, dielectric strength decreases.
16. The thickness of a material having a dielectric strength of 10MV/m is 5m, calculate the potential difference.
A. 2MV
B. 10MV
C. 50MV
D. 100MV
Answer: C
Dielectric strength is the potential gradient required to cause a breakdown in the material. The potential gradient is the ratio of voltage and thickness.
V = t × dielectric strength = 5 × 10 = 50MV.
17. Which medium has the highest dielectric strength?
A. Water
B. Mica
C. Air
D. Glass
Answer: C
The better material is to prevent electrical conductivity, the higher the dielectric strength. And the air is the best insulator so it has high dielectric strength.
18. Leakage in capacitors is primarily caused by _________
A. Transistors
B. Resistors
C. Inductors
D. DC motors
Answer: A
Leakage is primarily caused due to electronic devices, such as transistors, connected to the capacitors. Transistors conduct a small amount of current even when they are turned off, hence they are responsible for leakage current.
19. What is the conduction current when a capacitor is fully charged?
A. Infinity
B. Zero
C. 100A
D. 1000A
Answer: B
When a capacitor is fully charged, there is no conduction of electrons from one plate of the capacitor to another, hence there is no conduction current and the conduction current is equal to zero.
20. The flow of electrons in dielectric is due to _________
A. Conduction
B. Potential difference
C. Breakdown
D. Resistance
Answer: C
There is, under normal circumstances, no flow of electrons in a dielectric since a dielectric is an insulator. Hence, there is a flow of electrons in a dielectric only at breakdown voltage.
