In Joule's Law, what does q represent?

In Joule's Law, what does q represent?

• A. Electric charge
• B. Power
• C. Heat energy
• D. Electric potential

Answer: (C)

q represents heat energy, the energy transferred as heat to or from a system. In Joule’s law for a resistor, the heat produced over a time interval is q = I^2 R t, where I is the current and R is the resistance. This means q is the total amount of energy converted to heat, measured in joules. Since power is the rate of energy transfer (P = I^2 R), the accumulated heat over time is q = P t. The other quantities—electric charge and electric potential—are different physical concepts, so they don’t describe what q stands for here. The sign of q follows the usual convention: positive when heat flows into the system, negative when it leaves.

q represents heat energy, the energy transferred as heat to or from a system. In Joule’s law for a resistor, the heat produced over a time interval is q = I^2 R t, where I is the current and R is the resistance. This means q is the total amount of energy converted to heat, measured in joules. Since power is the rate of energy transfer (P = I^2 R), the accumulated heat over time is q = P t. The other quantities—electric charge and electric potential—are different physical concepts, so they don’t describe what q stands for here. The sign of q follows the usual convention: positive when heat flows into the system, negative when it leaves.