Question

solve the 26 number question.

Answer 1

Suppose, Internal Resistance = r

When the resistors are in parallel combination, then total resistance,

1/R1 = 1/2 + 1/2

1/R1 = 1

R1 = 1 ohm...●

And, Current = I1 = 1.2 A

Thus, emf of the cell = I1( R1 + r ).........equation 1.

Samely,

For Series combination,

R2 = 2 + 2

R2= 4 ohm...●

And, Current = I2 = 0.4 Ampere.

So, emf of the cell = I2(R2 + r).......equation 2.

Because, emf of the cell is same for all conditions, so from equation 1 and 2....

I1(R1 + r) = I2(R2 + r)

1.2(1 + r) = 0.4(4 + r)

3(1 + r) = 4 + r

3 + 3r = 4 + r

2r = 4 - 3

r = 1/2

r = 0.5 ohm....●●

Thus, Internal Resistance of the Cell = r = 0.5 ohm. ●


ii}. Now, emf of the cell,

From, equation 1.....

emf = I1( R1 + r )

= 1.2 ( 1 + 0.5 )

= 1.2 × 1.5

emf = 1.8 V...●●

Thus, emf of the cell = 1.8 V. ●

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Hope it was helpful.