If a circuit has 120 volts and 30 ohms resistance, the current is ______ amperes.

If a circuit has 120 volts and 30 ohms resistance, the current is ______ amperes.

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

Using Ohm's Law, current equals voltage divided by resistance: I = V / R. With 120 volts and 30 ohms, I = 120 / 30 = 4 amperes. This checks out because 30 Ω × 4 A = 120 V. If you used 2 A, 3 A, or 5 A, you’d need 60 Ω, 40 Ω, or 24 Ω respectively to maintain 120 V, which is not the given resistance. So the current is 4 amperes.

Using Ohm's Law, current equals voltage divided by resistance: I = V / R. With 120 volts and 30 ohms, I = 120 / 30 = 4 amperes. This checks out because 30 Ω × 4 A = 120 V. If you used 2 A, 3 A, or 5 A, you’d need 60 Ω, 40 Ω, or 24 Ω respectively to maintain 120 V, which is not the given resistance. So the current is 4 amperes.