If a circuit has a voltage of 9 V and a resistance of 3 Ω, what is the current?

• A. 1 A
• B. 3 A
• C. 6 A
• D. 9 A

Answer: (B)

Current in a circuit follows Ohm’s law: I = V / R. With a voltage of 9 volts and a resistance of 3 ohms, the current is I = 9 / 3 = 3 amperes. This shows how current is the rate at which charge flows, and how increasing voltage (at a fixed resistance) increases current, while increasing resistance (at a fixed voltage) decreases current. The 3 A result comes from dividing 9 by 3; different currents would require different resistance values.