What is the energy transfer formula for a resistor?

• A. E = I^2 R t
• B. E = I R t
• C. E = I^2 / R
• D. E = V^2 t

Answer: (A)

When current flows through a resistor, electrical energy is converted into heat in the resistor. The power dissipated (the rate of energy transfer) is P = I^2 R, or equivalently P = V^2 / R or P = VI. Since energy is power times time, the energy transferred over a time interval t is E = P t. Substituting P = I^2 R gives E = I^2 R t. This form aligns with units: I^2 R t = (A^2)(Ω)(s) = V·A·s = J, so it correctly represents energy. The other expressions don’t match energy units or the formula for power in a resistor, so they don’t describe the energy transferred.