The $SI$ unit of electric charge is $.........$

In a household electric circuit,different appliances are connected in parallel to one another. Give two reasons for this. An electrician puts a fuse of rating $5 \, A$ in that part of a domestic electrical circuit in which an electrical heater of rating $1.5 \, kW, 220 \, V$ is operating. What is likely to happen in this case and why? What change,if any,needs to be made?

The table given below provides the resistivity of three samples in $\Omega \cdot m$:

Sample	Resistivity $(\Omega \cdot m)$
$A$	$1.6 \times 10^{-8}$
$B$	$7.5 \times 10^{17}$
$C$	$44 \times 10^{-6}$

$(a)$ Which of them is a good conductor? Which is an insulator? Why?
$(b)$ $A$ wire of resistance $4 \ \Omega$ is folded on itself to double its thickness. Calculate the new resistance of the wire.

You are given three equal resistors. The number of resistances which can be obtained by joining them in series and in parallel grouping is

$A$ wire of length $L$ and resistance $R$ is stretched so that the length is doubled and area of cross-section is halved. How will its
$(a)$ resistance change?
$(b)$ resistivity change?

The $SI$ unit of resistivity of the material is $......$