If an electric current $I$ flows through a resistor $R$ in a circuit for time $t$,then the electrical energy $W$ consumed is given by:

What can be the difference between the specific resistance for a thin and thick wire made of the same material?

$(a)$ What is meant by saying that the potential difference between two points is $1$ volt?
$(b)$ Why does the connecting cord of an electrical heater not glow while the heating element does?
$(c)$ Electrical resistivities of some substances at $20^{\circ}C$ are given below:

Silver	$1.60 \times 10^{-8} \, \Omega m$
Copper	$1.62 \times 10^{-8} \, \Omega m$
Tungsten	$5.2 \times 10^{-8} \, \Omega m$
Iron	$10.0 \times 10^{-8} \, \Omega m$
Mercury	$94.0 \times 10^{-8} \, \Omega m$
Nichrome	$100 \times 10^{-6} \, \Omega m$

Answer the following questions in relation to them:
$(i)$ Among silver and copper, which one is a better conductor? Why?
$(ii)$ Which material would you advise to use in electrical heating devices? Why?

What are the essential requirements of a heater filament?

Electrical resistivity of a given metallic wire depends upon

Out of the two,a toaster of $1\, kW$ and an electric heater of $2\, kW$,which has a greater resistance?