A heating coil has a resistance of 22 Ω and can safely handle 15 A of current. What is the maximum voltage that it can be connected to without burning out?

• A. 330 V
• B. 165 V
• C. 660 V
• D. 24 V

Answer: (A)

The key idea is figuring out how voltage, current, and resistance relate for a safe operating limit. For a resistor-like heating coil, current equals the voltage divided by resistance (I = V/R). The coil has a maximum safe current of 15 A and a resistance of 22 Ω. To stay at that current limit, multiply the current by the resistance: 15 A × 22 Ω = 330 V. At 330 V, the current would be exactly 15 A, which is the safety threshold. Pushing voltages higher would push the current beyond what the coil can safely handle and could cause overheating. Using lower voltages keeps the current under the limit, which is safe but not at the maximum capacity. For reference, 165 V would give about 7.5 A, 660 V would push about 30 A, and 24 V would give about 1 A. So the maximum voltage that won’t burn out the coil is 330 V.