SATHEE: Current Electricity - Result Question 40

Current Electricity - Result Question 40

42. The internal resistance of a $2.1 V$ cell which gives a current of 0.2 A through a resistance of $10 Ω$ is

[2013]

(a) $0.5 Ω$

(b) $0.8 Ω$

(d) $0.2 Ω$

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Answer:

Correct Answer: 42. (a)

Solution:

(a) Given: $e m f ε = 2.1 V$

$I = 0.2 A, R = 10 Ω$

Internal resistance $r =$ ?

From formula.

$ε - I r = V = I R$

$2.1 - 0.2 r = 0.2 \times 10$

$2.1 - 0.2 r = 2$ or $0.2 r = 0.1$

$\Rightarrow r = \frac{0.1}{0.2} = 0.5 Ω$

$\begin{aligned} \frac{2}{잉} i = \frac{ε}{r + R} \Rightarrow 0.2 = \frac{2.1}{r + 10} \\ \Rightarrow 2.1 = 0.2 r + 2 \Rightarrow r = \frac{1}{2} = 0.5 Ω \end{aligned}$

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Current Electricity - Result Question 40

42. The internal resistance of a 2.1V cell which gives a current of 0.2 A through a resistance of 10Ω is

Answer:

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42. The internal resistance of a $2.1 V$ cell which gives a current of 0.2 A through a resistance of $10 Ω$ is