When a $12\, V$ battery is connected across an unknown resistor,there is a current of $2.5\, mA$ in the circuit. Find the value of the resistance of the resistor.

Why does the cord of an electric heater not glow while the heating element does?

Use the data in the table to answer the following: Which among iron and mercury is a better conductor?
< p style="text-align:center"> < span style="font-size:14px"> Electrical resistivity of some substances at $20\,^oC$

Material	Resistivity $(\Omega \,m)$
Iron	$10.0 \times 10^{-8}$
Mercury	$94.0 \times 10^{-8}$

What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?

What is meant by saying that the potential difference between two points is $1$ $V$?

The values of current $I$ flowing in a given resistor for the corresponding values of potential difference $V$ across the resistor are given below -

$I$ (amperes)	$0.5$	$1.0$	$2.0$	$3.0$	$4.0$
$V$ (volts)	$1.6$	$3.4$	$6.7$	$10.2$	$13.2$

Plot a graph between $V$ and $I$ and calculate the resistance of that resistor.