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In the given figure switches $S_{1}$ and $S_{2}$ are in open condition. The resistance across $a b$ when the switches $S_{1}$ and $S_{2}$ are closed is $...\,\Omega$
There are $0.8 \times 10^{23}$ free electrons $/ cm^3$ in copper. If $0.2\, A $ current is flowing is copper wire, then the drift velocity of electrons will be, if the cross sectional area of wire is $0.01 \,cm^2$
A $100\, W$ bulb $B_1$, and two $60\,W$ bulbs $B_2$ and $B_3$, are connected to a $250\, V$ source, as shown in the figure. Now $ W_1, W_2$ and $W_3$ are the output powers of the bulbs $B_1, B_2$ and $B_3$, respectively. Then
A wire of length ' $r$ ' and resistance $100 \Omega$ is divided into $10$ equal parts. The first $5$ parts are connected in series while the next $5$ parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:
Water of volume $2\, litre$ in a container is heated with a coil of $1\, kW$ at $27 \,^oC$. The lid of the container is open and energy dissipates at rate of $160\, J/s$. In how much time temperature will rise from $27\,^oC$ to $77\,^oC$ $[$ Given specific heat of water is $4.2\, kJ/kg$ $]$
A battery of internal resistance $4\, ohm$ is connected to the network of resistance as hown. In the order that the maximum power can be delivered to the network, the value of $R$ in ohm should be :-
A Daniel cell is balanced on $125\,cm$ length of a potentiometer wire. Now the cell is short-circuited by a resistance $2\, ohm$ and the balance is obtained at $100\,cm$. The internal resistance of the Daniel cell is .............. $ohm$
Four ammeters with identical internal resistance $r$ and a resistor $R$ are connected to a current source as given. if reading of $A_1$ and $A_2$ is $3\ A$ and $5\ A$ respectively then the reading $A_4$ is ............. $A$