How much resistance must be placed in a 120 volt circuit to limit the current to 2 amps?

How much resistance must be placed in a 120 volt circuit to limit the current to 2 amps?

• A. 120 ohms
• B. 60 ohms
• C. 30 ohms
• D. 240 ohms

Answer: (B)

Understanding Ohm's Law, which links voltage, current, and resistance, is key here. To limit the current to 2 A from a 120 V source, set R so that I = V / R equals 2. Solve for R: R = V / I = 120 V / 2 A = 60 ohms. With 60 ohms, the current is I = 120 V / 60 ohms = 2 A, exactly as desired. If you used a larger resistance, the current would drop below 2 A; if you used a smaller resistance, the current would rise above 2 A. So 60 ohms is the correct value.

Understanding Ohm's Law, which links voltage, current, and resistance, is key here. To limit the current to 2 A from a 120 V source, set R so that I = V / R equals 2. Solve for R: R = V / I = 120 V / 2 A = 60 ohms. With 60 ohms, the current is I = 120 V / 60 ohms = 2 A, exactly as desired. If you used a larger resistance, the current would drop below 2 A; if you used a smaller resistance, the current would rise above 2 A. So 60 ohms is the correct value.