Question 652: 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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