Question

In the given figure, A, B and C are three ammeters. The ammeter ‘B’ reads 0.5 A. (All the ammeters have negligible resistance):

Total resistance of the circuit is:

• A. 11 Ω
• B. 8 Ω
• C. 4 Ω
• D. 5 Ω

Answer 1

The correct option is (C) 4 Ω

The potential difference across 3-ohm resistor = $6\times 0.5=3V$

Reading in ammeter C ($I_c$) = $\frac{3}{3}=1A$

Reading in ammeter A ($I_A$) = $(1.0+0.5)=1.5A$

Equivalent resistance of the resistors connected in parallel

$\frac{1}{R_e}=\frac{1}{6}+\frac{1}{3}=\frac{1}{2}$

So, $R_e=2$ ohm

This equivalent resistance is in series with the next resistance

So, $R_{equivalent}=2+2=4$ ohm

Hence the total resistance of the circuit is 4 ohm.