Question

Two identical electric lamps marked 500 W, 220 V are connected in series and then joined to a 110 V line. The power consumed by each lamp is

• A. $\frac{125}{4}\mspace{6mu} W$
• B. $\frac{25}{4}\mspace{6mu} W$
• C. $\frac{225}{4}\mspace{6mu} W$
• D. 125 W

Answer 1

Answer: (A)

$\frac{125}{4}\mspace{6mu} W$

Answer 2

Both bulbs are identical so voltage across each bulb will be 55V.

Hence power consumed by each bulb is

$\left( \frac{V_{A}}{V_{R}} \right)^{2} \times P_{R} = \left( \frac{55}{220} \right)^{2} \times 500 = \frac{125}{4}W$