Praxis Study Companion – Physics (5266) Practice Test

Ohm’s law and how power is dissipated in a resistor are being tested here. The current through a resistor follows I = V/R. With a 12 V source and a 3 Ω resistor, the current is 12/3 = 4 A. The power the resistor dissipates as heat is P = VI, so P = 12 V × 4 A = 48 W. You can also confirm this with P = I^2R or P = V^2/R, both giving 48 W. So the current is 4 A and the resistor dissipates 48 W.