A lamp is connected to a 240 V supply and has a power rating of 120 W. What is the current through the lamp?

• A. 0.25 A
• B. 0.4 A
• C. 0.5 A
• D. 0.6 A

Answer: (C)

Power is the product of voltage and current (P = V × I). With a lamp rated at 120 W on a 240 V supply, the current is I = P / V = 120 / 240 = 0.5 A. This also checks out because 240 V × 0.5 A = 120 W. So the lamp draws 0.5 A at 240 V.