Which device works on the heating effect of electric current?

The electrical appliance having higher power draws a larger current.

In an electrical circuit,two resistors of $2\,\Omega$ and $4\,\Omega$ respectively are connected in series to a $6\,V$ battery. The heat dissipated by the $4\,\Omega$ resistor in $5\,s$ will be ........ $J$.

$A$ piece of wire is redrawn,without change in volume,so that its radius is halved. Compare the new resistance with the original resistance.

$(a)$ Define the term 'volt'.
$(b)$ State the relation between work,charge,and potential difference for an electric circuit. Calculate the potential difference between the two terminals of a battery,if $100 \ J$ of work is required to transfer $20 \ C$ of charge from one terminal of the battery to the other.

How can we maintain a potential difference across a conductor?