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Two cells, $e.m.f.$ of each is $E$ and internal resistance $r$ are connected in parallel between the resistance $R$. The maximum energy given to the resistor will be, only when
A $500\, W$ heating unit is designed to operate from a $115\, volt$ line. If the line voltage drops to $110\, volt$, the percentage drop in heat output will be ............... $\%$
A silver and zinc voltameter are connected in series and a current $i$ is passed through them for a time $t$ liberating $W\, gm$ of zinc. The weight of silver deposited is nearly ..............$W$
Two electric bulbs whose resistance are in the ratio of $1: 2$, are connected in parallel to a constant voltage source. The power dissipated in them has the ratio
In the following diagram, the lengths of wires $A B$ and $B C$ are equal, but the radius of wire $A B$ is double that of $B C$. The ratio of potential gradient on wires $A B$ and on $B C$ will be (wires are made of same material)
Two batteries one of the $\mathrm{emf}$ $3\,V$, internal resistance $1$ ohm and the other of $\mathrm{emf}$ $15\, V$, internal resistance $2$ $\mathrm{ohm}$ are connected in series with a resistance $R$ as shown. If the potential difference between $a$ and $b$ is zero the resistance of $R$ in $\mathrm{ohm}$ is
Two electric bulbs, rated at $(25\, W, 220\, V)$ and $(100\, W, 220\, V)$, are connected in series acroos a $220\, V$ voltage source. If the $25\, W$ and $100\, W$ bulbs draw powers $P_1$ and $P_2$ respectively, then
A resistance of $2 \Omega$ is comnected across one gap of a metre-bridge (the length of the wire is $100 \mathrm{~cm}$ ) and an unknown resistance, greater than $2 \Omega$, is connected across the other gap. When these resistance are interchanged, the balance point shifts by $20 \mathrm{~cm}$. Neglecting any corrections, the unknown resistance is
A potentiometer has uniform potential gradient across it. Two cells connected in series $(i)$ to support each other and $(ii)$ to oppose each other are balanced over $6\,m$ and $2\,m$ respectively on the potentiometer wire. The $e.m.f.$’s of the cells are in the ratio of