JEE MAIN - Physics (2004 - No. 20)
In a meter bridge experiment null point is obtained at $$20$$ $$cm$$, from one end of the wire when resistance $$X$$ is balanced against another resistance $$Y.$$ If $$X < Y$$, then where will be the new position of the null point from the same end, if one decides to balance a resistance of $$4$$ $$X$$ against $$Y$$
$$40$$ $$cm$$
$$80$$ $$cm$$
$$50$$ $$cm$$
$$70$$ $$cm$$
Explanation
In the first case $${X \over Y} = {{20} \over {80}} = {1 \over 4}$$
In the second case $${{4X} \over Y} = {\ell \over {100 - \ell }} \Rightarrow \ell = 50$$
In the second case $${{4X} \over Y} = {\ell \over {100 - \ell }} \Rightarrow \ell = 50$$
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