What does resistance refer to in a circuit?

Resistance is a measure of the opposite to current flow in an electrical circuit. Resistance is measured in ohms.

Hope this helps

The heat developed can be calculated using the power rules as follows:

P = I x V = I^2 x R

First solution is to use the given values of I and R as follows:
P = I^2 x R = (2)^2 x 25 = 4 x 25 = 100 watt

Second solution is to use ohm's law to get V, then substitute to get the power as follows:
V = I x R = 2 x 25 = 50 volts
Power = V x I = 50 x 2 = 100 watt