Which set of quantities is sufficient to determine heat energy q in Joule's Law?

Which set of quantities is sufficient to determine heat energy q in Joule's Law?

• A. I, E, R
• B. E, I, t
• C. I, R, t
• D. E, R, t

Answer: (C)

The heat energy produced by a resistor is determined by q = I^2 R t. So knowing the current, the resistance, and the duration lets you calculate q directly: you square the current, multiply by the resistance, and multiply by time. This trio is sufficient because it directly plugs into the standard form for electrical heating. Without all three—if any one is missing—you can’t uniquely determine the heat produced (for example, same current and time with different resistances would yield different q). While another form like q = V I t could work if voltage were known instead, the combination of I, R, and t matches the common expression and provides a complete, sufficient set.

The heat energy produced by a resistor is determined by q = I^2 R t. So knowing the current, the resistance, and the duration lets you calculate q directly: you square the current, multiply by the resistance, and multiply by time. This trio is sufficient because it directly plugs into the standard form for electrical heating. Without all three—if any one is missing—you can’t uniquely determine the heat produced (for example, same current and time with different resistances would yield different q). While another form like q = V I t could work if voltage were known instead, the combination of I, R, and t matches the common expression and provides a complete, sufficient set.