Question

Two identical cells connected in series send 1.0A current through a 5 Ω resistor. When they are connected in parallel, they send 0.8 A current through the same resistor. What is the internal resistance of the cell?
(a) 0.5 Ω
(b) 1.0 Ω
(c) 1.5 Ω
(d) 2.5 Ω

Answer 1

Answer:

D) 2.5Ω

Explanation:

Let the emf of each cells be = E

Internal resistance = r

In a series combination by applying kvl -

2E = 10(2r+5) - eq 1

In parallel combination applying kvl will be given as -

ip = E1+E2/r+2R

8 = 2E/(r+2×5)

= 2E = 8(r+2×5) - eq 2

Using equation 1 and 2

= 10(2r+5) = 8(r+2×5)

= 2.5 Ω

Therefore the internal resistance of the cell is 2.5 Ω

Answer 2

Answer:

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