An electric blub of $60 \mathrm{~W}, 120 \mathrm{~V}$ is to be connected to 220 V source. What resistance should be connected in series with the bulb, so that the bulb glows properly?

In an experiment to determine the temperature coefficient of resistance of a conductor, a coil of wire $X$ is immersed in a liquid. It is heated by an external agent. A meter bridge set up is used to determine resistance of the coil $X$ at different temperatures. The balancing points measured at temperatures $t_1=0^{\circ} \mathrm{C}$ and $t_2=100^{\circ} \mathrm{C}$ are 50 cm and 60 cm respectively. If the standard resistance taken out is $S=4 \Omega$ in both trials, the temperature coefficient of the coil is

A wire of resistance $$R$$ is connected across a cell of emf $$(\varepsilon)$$ and internal resistance $$(r)$$. The current through the circuit is $$I$$. In time $$t$$, the work done by the battery to establish the current $$I$$ is

For a given electric current the drift velocity of conduction electrons in a copper wire is $$v_d$$ and their mobility is $$\mu$$. When the current is increased at constant temperature