How does the resistivity of alloys compare with those of pure metals from which they may have been formed?

$(a)$ 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.

The $V-I$ graph for series and parallel combination of two metallic resistors is as shown in the figure. Which graph represents parallel combination? Justify your answer.

An electric heater draws a current of $2\;A$ when connected to a voltage source of $120\;V$. What is the resistance of the heater coil?

If the charge on an electron is $1.6 \times 10^{-19} \text{ C}$,find the approximate number of electrons in $1 \text{ C}$.

$(a)$ Why is the series arrangement not used for domestic circuits?
$(b)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(c)$ Why are the conductors of electric heating devices,such as bread toasters and electric irons,made of an alloy rather than a pure metal?
$(d)$ Why are copper and aluminium wires usually employed for electricity transmission?
$(e)$ Why does the cord of an electric heater not glow while the heating element does?