Question

Four bulbs $B_1,B_2,B_3$ and $B_4$ of $100W$ each are connected to $220V$ main as shown in the figure. The reading in an ideal ammeter will be :

• A. 0.45 A
• B. 0.90 A
• C. 1.35 A
• D. 1.80 A

Answer 1

Answer: (C)

Resistance of any bull
$R=\frac{V^2}{P}=\frac{(220{)}^2}{100}=484\Omega$
Net resistance of the cks
$R_{eq}=\frac{R}{4}=\frac{484}{4}=121\Omega$
$v=i{R}_{eq}$
$220\times i\times 121$
$i=1.81$ Amp. (total current supplied by the battery)
Current in each branch in $i=\frac{1.81}{4}$ amp.
$=0.45$ amp.
Reading of ammeter $=3\times 0.45=1.3575$ amp.