Current Electricity - Electromagnetism - Physics Previous Year Questions

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

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

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

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 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

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

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