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

What is meant by resistance of a conductor? Name and define its $SI$ unit. List the factors on which the resistance of a conductor depends. How is the resistance of a wire affected if
$(i)$ its length is doubled,
$(ii)$ its radius is doubled?

An electric iron has a rating of $750\, W; 200\, V$. Calculate:
$(i)$ The current required.
$(ii)$ The resistance of its heating element.
$(iii)$ Energy consumed by the iron in $2$ hours.

Explain the terms potential and potential difference. Give their $SI$ units.

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.

The rating of an electric heater is $1100 \ W, 220 \ V$. Calculate its resistance when it operates at $220 \ V$. Also,calculate the energy consumed in $kWh$ in the month of November,if the heater is used daily for four hours at the rated voltage.