A circuit has a resistance of 20 Ω and a voltage across it of 60 V. What is the current?

A circuit has a resistance of 20 Ω and a voltage across it of 60 V. What is the current?

• A. 3 A
• B. 1 A
• C. 12 A
• D. 60 A

Answer: (A)

Current in a circuit comes from Ohm’s law: current equals voltage divided by resistance. Here, 60 volts across 20 ohms gives I = 60/20 = 3 amperes. The unit ampere comes from voltage per ohm, since 1 ohm is the resistance that would allow 1 ampere to flow with 1 volt of pressure. If the resistance were larger, the current would be smaller; if it were smaller, the current would be larger. For example, with the same 60 volts, 60 ohms would yield 1 A, 5 ohms would yield 12 A, and 1 ohm would yield 60 A. So 3 A is the correct current.

Current in a circuit comes from Ohm’s law: current equals voltage divided by resistance. Here, 60 volts across 20 ohms gives I = 60/20 = 3 amperes. The unit ampere comes from voltage per ohm, since 1 ohm is the resistance that would allow 1 ampere to flow with 1 volt of pressure. If the resistance were larger, the current would be smaller; if it were smaller, the current would be larger. For example, with the same 60 volts, 60 ohms would yield 1 A, 5 ohms would yield 12 A, and 1 ohm would yield 60 A. So 3 A is the correct current.