Answer the following questions related to the heating effect of an electric current.
(i) State Joule’s law of heating.
(ii) Starting from the definition of electric power, derive the expression that relates the heat produced in a conductor to the current through it, its resistance and the time for which the current flows.
(iii) By what factor will the heat produced in a conductor change if (a) the current through it is doubled while its resistance remains the same, and (b) its resistance is doubled while the current remains the same? Show your reasoning in each case.
(iv) Name any two household appliances that make use of the heating effect of electric current and explain briefly how this effect is utilised in each.