Question 681: Current Electricity

Question

A current of 2 A flows through a 2 $$\Omega $$ resistor when connected across a battery a 2 $$\Omega $$ resistor when connected across a battery. The same battery supplies a current of 0.5 A  when connected across a 9 $$\Omega $$ resistor. The internal resistance of the battery is

Accepted Answer

Let $$\varepsilon $$ be the emf and r be internal resistance of the battery.
In the first case,
$$2 = {\varepsilon  \over {2 + r}}$$
In the second case,
$$0.5 = {\varepsilon  \over {9 + r}}$$
Divide (i) by (ii), we get
$${2 \over {0.5}} = {{9 + r} \over {2 + r}} \Rightarrow 4 + 2r = 4.5 + 0.5r$$
$$1.5r = 0.5 \Rightarrow r = {{0.5} \over {1.5}} = {1 \over 3}\Omega $$

Answer

0.5 $$\Omega $$

Answer

1/3 $$\Omega $$

Answer

1/4 $$\Omega $$

Answer

1 $$\Omega $$

Current Electricity

A current of 2 A flows through a 2 $\Omega resistor when connected across a battery a 2 \Omega resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 \Omega $ resistor. The internal resistance of the battery is

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