The circuit shown in the figure contains three resistors R1=100 Ω, R2=50 Ω and R3=20 Ω and cells of E.M.F.s E 1'=2 V and E 2 . The ammeter indicates a current of 50 mA. Find the E.M.F. (in V) of the second cell. (The internal resistance of the ammeter and of the cell should be neglected)

Question

The circuit shown in the figure contains three resistors R1=100 Ω, R2=50 Ω and R3=20 Ω and cells of E.M.F.s E 1'=2 V and E 2 . The ammeter indicates a current of 50 mA. Find the E.M.F. (in V) of the second cell. (The internal resistance of the ammeter and of the cell should be neglected) (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

Using KVL: 100( i +0.05)+50 i -2=0 150 i +3=0 i =(-3/150)=-0.02 A =-20 mA So, the direction of i is opposite to what we have assumed. If we redraw the circuit.

Using KVL: 20 × 0.5+100 × 0.03- V 2=0 1+3- V 2=0 V2=4 V2

Using KVL: 100(i+0.05)+50i−2=0 150i+3=0 i=150−3​=−0.02A=−20mA So, the direction of i is opposite to what we have assumed. If we redraw the circuit. Using KVL : 20×0.5+100×0.03−V2​=0 1+3−V2​=0 V2​=4V2

Using $K V L :$
$100 (i + 0.05) + 50 i - 2 = 0$
$150 i + 3 = 0$
$i = \frac{- 3}{150} = - 0.02 A = - 20 m A$
So, the direction of i is opposite to what we have assumed.
If we redraw the circuit.

Using $K V L$ :
$20 \times 0.5 + 100 \times 0.03 - V_{2} = 0$
$1 + 3 - V_{2} = 0$
$V_{2} = 4 V^{2}$