The total power consumed by four 30-watt lamps connected in parallel to a 12-volt supply is

The total power consumed by four 30-watt lamps connected in parallel to a 12-volt supply is

• A. 60 W
• B. 120 W
• C. 30 W
• D. 240 W

Answer: (B)

When devices are in parallel, the same supply voltage is across each one, so each device dissipates its rated power independently. Here, each lamp is 30 W at 12 V, so four identical lamps will consume 4 × 30 W = 120 W in total. You can also see this from current: each lamp draws I = P/V = 30/12 = 2.5 A, so four lamps draw 10 A; total power is V × I = 12 × 10 = 120 W. The other amounts correspond to different numbers of lamps or different operating conditions, not the four-lamp setup described.

When devices are in parallel, the same supply voltage is across each one, so each device dissipates its rated power independently. Here, each lamp is 30 W at 12 V, so four identical lamps will consume 4 × 30 W = 120 W in total. You can also see this from current: each lamp draws I = P/V = 30/12 = 2.5 A, so four lamps draw 10 A; total power is V × I = 12 × 10 = 120 W. The other amounts correspond to different numbers of lamps or different operating conditions, not the four-lamp setup described.