A $dc$ source of $emf \,E_1 = 100\,V$ and internal resistance $r = 0.5\,\Omega ,$ a storage battery of emf $E_2 = 90\,V$ and an external resistance $R$ are connected as shown in figure. For what value of $R$ no current will pass through the battery ? ................ $\Omega$
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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 $.......$
Twelve resistors each of resistance $16 \,\Omega $ are connected in the circuit as shown. The net resistance between $AB$ (any two conjugate points of outer square) is ............... $\Omega$
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 $..........\Omega$
When $5\ V$ potential difference is applied across a wire of length $0.1\ m$, the drift speed of electrons is $2.5 \times 10^{-4}$ $ms^{-1}$ . If the electron density in the wire is $8 \times 10^{28}$ $m^{-3}$ the resistivity of the material is close to
In a meter bridge, the null point is found at a distance of $25\, cm$ from $A$ . If now a resistance of $10\,\Omega $ is connected in parallel with $S$, the null point occurs at mid point of $AB$. The value of $R$ is .............. $\Omega$