In the heat input equation H = I^2 R T, which variable is squared?

• A. Current I
• B. Resistance R
• C. Time T
• D. Heat H

Answer: (A)

The heat produced by electrical current depends on the square of the current. This comes from Joule’s law, which states that power converted to heat in a resistor is P = I^2 R. To get the total heat (energy) over a time interval, you multiply that power by the duration, giving H = I^2 R T. So the variable that is squared in the equation is the current I. Resistance and time influence the amount of heat, but they are not squared themselves. The heat is the result of this relationship, not a squared quantity.