If a circuit has a 120 V supply and a 24 Ω resistor, what is the current through the resistor?

• A. 0.5 A
• B. 2 A
• C. 5 A
• D. 10 A

Answer: (C)

Current is determined by Ohm’s law: I = V / R. With a 120 V supply across a 24 Ω resistor, the current is I = 120 / 24 = 5 A. This shows how voltage pushes charges through the resistance, and how the resistance value sets how much current flows. If you imagine different currents, 0.5 A would need a resistance of 240 Ω, 2 A would need 60 Ω, and 10 A would need 12 Ω, but for these given numbers the current is 5 A.