If a circuit has a resistance of 30 ohms and is supplied with 60 volts, what is the power?

If a circuit has a resistance of 30 ohms and is supplied with 60 volts, what is the power?

• A. 60 W
• B. 120 W
• C. 180 W
• D. 360 W

Answer: (B)

Power in a DC circuit is the rate at which energy is delivered. Use P = VI or P = V^2 / R. First find the current: I = V / R = 60 V / 30 Ω = 2 A. Then P = VI = 60 V × 2 A = 120 W. (Check with P = V^2 / R: 60^2 / 30 = 3600 / 30 = 120 W.) Other values would require different currents or resistances not given here, so they don’t fit the provided V and R.

Power in a DC circuit is the rate at which energy is delivered. Use P = VI or P = V^2 / R. First find the current: I = V / R = 60 V / 30 Ω = 2 A. Then P = VI = 60 V × 2 A = 120 W. (Check with P = V^2 / R: 60^2 / 30 = 3600 / 30 = 120 W.)

Other values would require different currents or resistances not given here, so they don’t fit the provided V and R.