The correct answer is: D. none of the above
Dielectric strength is the maximum electric field strength that an insulating material can withstand without breaking down and becoming conductive. It is usually measured in volts per meter (V/m).
The dielectric strength of a material is affected by a number of factors, including temperature, moisture content, and the presence of impurities. In general, dielectric strength decreases with increasing temperature and moisture content. The presence of impurities can also reduce dielectric strength.
The dielectric strength of a material is an important property that is used in the design of electrical equipment. For example, the insulation used in high-voltage cables must have a high dielectric strength to prevent breakdown and arcing.
Here are some additional details about each of the options:
- A. increases with rise in temperature
This is not always the case. In fact, the dielectric strength of some materials decreases with increasing temperature. For example, the dielectric strength of paper decreases by about 50% for every 10°C increase in temperature.
- B. increases with moisture content
This is also not always the case. In fact, the dielectric strength of some materials decreases with increasing moisture content. For example, the dielectric strength of paper decreases by about 20% for every 1% increase in moisture content.
- C. is same for all insulating materials
This is definitely not the case. The dielectric strength of different materials can vary widely. For example, the dielectric strength of air is about 100,000 V/m, while the dielectric strength of mica is about 10,000,000 V/m.