If $4.8 \text{ A}$ current is passed through an electrical appliance,then the number of electrons passing through it in $1 \text{ second}$ will be $......$

$(a)$ 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?

$1\, \mu A = \dots \dots \dots \,mA$

$A$ metal has a very large number of free electrons and a non-metal has a very small number of free electrons.

In an electrical circuit,three incandescent bulbs $A, B$ and $C$ of rating $40 \, W, 60 \, W$ and $100 \, W$ respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

What type of electric charge does a proton possess?