A material '$B$' has twice the specific resistance of '$A$'. A circular wire made of '$B$' has twice the diameter ofa wire made of '$A$'. then for the two wires to have the same resistance, the ratio $\frac{{{l_B}}}{{{l_A}}}$ of their respective lengths must be
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The resistance of a $5\, cm$ long wire is $10\, \Omega$. It is uniformly stretched so that its length becomes $20\, cm$. The resistance of the wire is ............. $\Omega$
Equal potentials are applied on an iron and copper wire of same length. In order to have the same current flow in the two wires, the ratio $r$ (iron)/$r$ (copper) of their radii must be (Given that specific resistance of iron = $1.0 \times {10^{ - 7}}$ $ ohm-m$ and specific resistance of copper = $1.7 \times {10^{ - 8}}\,ohm-m$)
Two resistors $400\, \Omega$ and $800\, \Omega$ are connected in series across a $6 V$ battery. The potential difference measured by a voltmeter of $10\, k \Omega$ across $400\, \Omega$ resistor is close to$....V$
A meter bridge is set up as shown, to determine an unknown resistance ' $X$ ' using a standard $10\,ohm$ resistor. The galvanometer shows null point when tapping-key is at $52\,cm$ mark. The endcorrections are $1\,cm$ and $2\,cm$ respectively for the ends $A$ and $B$. The determined value of ' $X$ ' is $..........\Omega$
In a Wheatstone's bridge, three resistances $P, Q$ and $R$ connected in the three arms and the fourth arm is formed by two resistances $S_1$ and $S_2$ connected in parallel. The condition for the bridge to be balanced will be