A 24 V DC source connected to a 6 Ω resistor. Calculate current and power dissipated.

• A. I = 2 A; P = 48 W
• B. I = 4 A; P = 96 W
• C. I = 6 A; P = 144 W
• D. I = 1 A; P = 24 W

Answer: (B)

Ohm's law and power calculations link voltage, current, and resistance, and show how to find both current and the heat dissipated in a resistor. With 24 V across a 6 Ω resistor, the current must be I = V/R = 24/6 = 4 A. The power dissipated is P = V × I = 24 × 4 = 96 W (also P = I^2 R = 4^2 × 6 = 96 W). The other values would require a different resistance to keep the same voltage or a different voltage to keep that current—for example, 2 A would need a 12 Ω resistor, 6 A would need 4 Ω, and 1 A would need 24 Ω.