Physics Questions

No work done as there is no external external pressure in free expansion. 

Hence, Work done in a free expansion process is Zero.

Graphite is a good conductor of electricity as it contains free electrons to move through the structure of the graphite.

The capacity of a water heater is measured in Gallons or Liters. In the USA, it is measured in Gallons and in India, we measure it in Liters.

Hence, if the capacity of the water heater is 15 gallons or 15 liters, then it says that it can hold 15 gallons or 15 liters of water.

Resistivity :

Resistivity is a measure of the resistance to the flow of electrons. 

Conductivity :

Conductivity is just the inverse of resistivity, σ = 1/ρ, where σ is conductivity and ρ is resistivity.

Example:

Think of a pipe and water, the bigger the pipe, the easier water can flow and thus the lower the resistance.