What happens when current flows through a resistance?

• A. Heat is produced
• B. No heat is produced
• C. The resistance increases without heating
• D. The current stops

Answer: (A)

When current flows through a resistor, electrical energy is converted into thermal energy. Electrons collide with the atoms in the resistor’s material, and these collisions transfer energy to the lattice. That energy shows up as heat. The rate of heat production, or power dissipated as heat, is P = I^2R (or equivalently P = V^2/R), so more current or a larger resistance means more heat. So heat being produced is the expected outcome of current through a resistor. Saying no heat is produced would be incorrect, and claiming the resistance just increases without heating conflicts with how resistors convert electrical energy into thermal energy. If the current stopped, that would be due to the circuit opening, not the normal behavior of a resistor under current.