Figure shows a cross-section of a large-section of an infinite metal sheet carrying an electric current along its surface. The current per unit length is $J$ . A current carrying square loop is placed nearby the metal sheet such that the plane of square is perpendicular to the plane of sheet then
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A cell of internal resistance $r$ drives current through an external resistance $R$ . The power delivered by the cell to the external resistance will be maximum when:
A potentiometer consists of two wires $AC$ and $CB$ of same material and of equal lengths but diameters in the ratio $3 : 1.$ Then the potential gradients on the two wires will be in the ratio :-
Three $60\, W$ light bulbs are mistakenly wired in series and connected to a $120\,V$ power supply. Assume the light bulbs are rated for single connection to $120\,V$. With the mistaken connection, the power dissipated by each bulb is: .................. $W$
Two wires that are made up of two different materials whose specific resistance are in the ratio $2 : 3$, length $3 : 4$ and area $4 : 5$. The ratio of their resistances is
In a potentiometer experiment two cells of $e.m.f.$ $E_1$ and $E_2$ are used in series and in conjunction and the balancing length is found to be $58\, cm$ of the wire. If the polarity of $E_2$ is reversed, then the balancing length becomes $29\, cm$. The ratio $\frac{{{E_1}}}{{{E_2}}}$ of the $e.m.f.$ of the two cells is
Resistance of $100\, cm$ long potentiometer wire is $10 \,\Omega$, it is connected to a battery ($2\, volt$) and a resistance $R$ in series. A source of $10\, mV$ gives null point at $40\, cm$ length, then external resistance $R$ is ........... $\Omega $