36 cells each of internal resistance $0.5 \Omega$ and emf 1.5 V each are used to send current through an external circuit of $2 \Omega$ resistor. For getting maximum current, $n$ cells are combined in series in each row. If total number of such rows are $m$, then the value of $(n / m)$ will be

The maximum power rating of a $20 \Omega$ resistor is 2 kW . Then, it cannot be used with 300 V DC source because the

The magnitude of resistance $X$ in the circuit shown below in the figure, when no current flows through the $5 \Omega$ resistor, is

A constant voltage is applied between the two ends of a uniform metallic wire, Some heat is developed in it. The heat developed is halved if

24 cells of emf $$1.5 \mathrm{~V}$$ each having internal resistance of $$1 \mathrm{~ohm}$$ are connected to an external resistance of $$1.5 \mathrm{~ohms}$$. To get maximum current

A silver wire of radius $$0.1 \mathrm{~cm}$$ carries a current of $$2 \mathrm{~A}$$. If the charge density in silver is $$5.86 \times 10^{28} \mathrm{~m}^{-3}$$, the drift velocity is

An electron revolves in a circle at the rate of $$10^{19}$$ rounds per second. The equivalent current is $$\left(e=1.6 \times 10^{-19} \mathrm{C}\right)$$

The temperature coefficient of the resistance of a wire is 0.00125 per $${ }^{\circ} \mathrm{C}$$. At $$300 \mathrm{~K}$$ its resistance is $$1 \Omega$$. The resistance of wire will be $$2 \Omega$$ at