The unit of electric current,$.......$,is also called an ampere,named after André-Marie Ampère.

Mention the condition under which charges can move in a conductor. Name the device which is used to maintain this condition in an electric circuit.

The potential difference between the terminals of an electric heater is $60\, V$ when it draws a current of $4\, A$ from the source. What current will the heater draw,if the potential difference is increased to $120\, V$ (in $, A$)?

When an electric iron is connected to a $220\;V$ line and a current of $5\;A$ flows through it,what is the power of the iron?

$A$ current of $1\, A$ is drawn by a filament of an electric bulb. The number of electrons passing through a cross-section of the filament in $16$ seconds would be roughly:

$(a)$ Why are copper or aluminium wires generally used for electrical transmission and distribution purposes?
$(b)$ Two wires,one of copper and the other of manganin,have equal lengths and equal resistances. Which wire is thicker? Given that the resistivity of copper is lower than that of manganin.