The electromotive force of a primary cell is $2\, volts$. When it is short-circuited it gives a current of $4$ amperes. Its internal resistance in $ohms$ is
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The length of a metallic wire is increased by $20 \%$ and its area of cross section is reduced by $4 \%$. The percentage change in resistance of the metallic wire is $.......$
In the given circuit the internal resistance of the $18\,V$ cell is negligible. If $R_1 = 400 \,\Omega ,\,R_3 = 100\,\Omega $ and $R_4 = 500\,\Omega $ and the reading of an ideal voltmeter across $R_4$ is $5\,V,$ then the value of $R_2$ will be ........... $\Omega$
Two identical cells, when connected either in parallel or in series gives same current in an external resistance $5\,\Omega$. The internal resistance of each cell will be $.............\,\Omega$.
Some electric bulbs are connected in series across a $220\, V$ supply in a room. If one bulb is fused then remaining bulbs are connected again in series across the same supply. The illumination in the room will
A wire of resistance $R$ and radius $r$ is stretched till its radius became $r / 2$. If new resistance of the stretched wire is $x R$, then value of $x$ is $\qquad$
A cell whose e.m.f. is $2\, V$ and internal resistance is $0.1\,\Omega $, is connected with a resistance of $3.9\,\Omega $. The voltage across the cell terminal will be ................ $V$