Which statement about energy balance is true for a heater that uses electrical energy to produce heat?

• A. Electrical energy is converted entirely to light energy.
• B. Electrical energy is converted to thermal energy.
• C. Thermal energy is created from nowhere.
• D. Electrical energy doubles as mechanical energy.

Answer: (B)

Energy balance for a heater is about how electrical energy is transformed into another form. In a heater, the electric current passes through a resistive element and experiences resistance. The collisions and interactions convert electrical energy into heat energy — this is resistive (or Joule) heating. The heat then raises the temperature of the heater and its surroundings. So the input electrical energy is transformed into thermal energy.

It isn’t created from nowhere, and it isn’t converted entirely into light, nor does the device inherently produce mechanical energy. Therefore, the statement that best describes the energy flow is that electrical energy is converted to thermal energy.