Question

In the circuit shown in figure, ammeter and voltmeter are ideal. If $E=4V,R=9\Omega$ and $r=1\Omega$, then readings of ammeter and voltmeter are

• A. $A_m=1A$
• B. $A_m=2A$
• C. $V_m=3V$
• D. $V_m=4V$

Answer 1

Answer: (A), (C)

The correct options are
A $V_m=3V$
C $A_m=1A$

Looking at the loop with first two resistors, we can say that current in the two resistors will be equal and opposite. Similarly, in the loop with last two resistors, current will be equal and opposite.

L: Left, R: Right

In first resistor, i flows L to R.

In second resistor, i flows R to L.

In third resistor, i flows L to R.

Therefore, current in ammeter will be 3i R to L. Hence, applyin KVL,

$4=\left(3i\right)\left(1\right)+\left(i\right)\left(9\right)$

$i=\frac{1}{3}A$

Therefore, ammeter reading will be $3i=3X\frac{1}{3}A=1A$.

And voltmeter reading will be $V=iR=9X\frac{1}{3}V=3V$.