Question

Four identical bulbs each rated $100W$ at $220V$and two bulb each of $200W$ at $220V$ are connected with a battery as shown in the figure. The total electric power consumed by the bulbs is

• A. 75 watt
• B. 80 watt
• C. 20 watt
• D. 800 watt

Answer 1

Answer: (B)

80 watt

As shown in circuit, the 200W bulbs are connected in parallel to each other and in series with the supply. Also, 100W bulbs are connected in parallel to each other and supply.
Therefore,
$P_s=100+100+100+100=400$

$\frac{1}{P_{eq}}=\frac{1}{200}+\frac{1}{P_s}+\frac{1}{200}$

$\frac{1}{P_{eq}}=\frac{1}{200}+\frac{1}{400}+\frac{1}{200}$

$\frac{1}{P_{eq}}=\frac{5}{400}$

$P_{eq}=80watt$