Find the applied voltage when the current is 30 A and the resistance is 4 Ω.

Find the applied voltage when the current is 30 A and the resistance is 4 Ω.

• A. 60V
• B. 240V
• C. 120V
• D. 12V

Answer: (C)

Voltage is found by multiplying current by resistance, which is Ohm’s law. With 30 amperes flowing through 4 ohms, the voltage is V = I × R = 30 × 4 = 120 volts. So the applied voltage is 120 volts. If you imagine different scenarios to see why the other numbers don’t fit: a voltage of 60 V would occur with 30 A and 2 Ω, 240 V would need 8 Ω, and 12 V would need only 0.4 Ω. The given values point directly to 120 volts.

Voltage is found by multiplying current by resistance, which is Ohm’s law. With 30 amperes flowing through 4 ohms, the voltage is V = I × R = 30 × 4 = 120 volts. So the applied voltage is 120 volts. If you imagine different scenarios to see why the other numbers don’t fit: a voltage of 60 V would occur with 30 A and 2 Ω, 240 V would need 8 Ω, and 12 V would need only 0.4 Ω. The given values point directly to 120 volts.