Question

The following table shows current in Amperes and potential difference in Volts.

a. Find the average resistance.

b. What will be the nature of the graph between the current and potential difference? (Do not draw a graph.)

c. Which law will the graph prove? Explain the law.

V (Volts)	I (Amp)
4	9
5	11.25
6	13.5

Answer 1

a. From Ohm's law, we have
$R=\frac{V}{I}$

V (volts)	I (amp)	R (ohm)
4	9	$\frac{4}{9}$
5	11.25	$\frac{4}{9}$
6	13.5	$\frac{4}{9}$

Therefore, average resistance = $\frac{\frac{4}{9}+\frac{{\displaystyle 4}}{{\displaystyle 9}}+\frac{{\displaystyle 4}}{{\displaystyle 9}}=\frac{12}{9}}{3}=\frac{4}{3\times 3}=\frac{4}{9}\mathrm{\Omega }$

b. The nature of the graph between the current and potential difference will be a straight line.

c. The graph proves Ohm's law. Ohm's law states that, under constant temperature and physical conditions, the current flowing through a conductor is always proportional to the potential difference across it i.e.
$V\propto I$
or, V = RI
where R is a constant of proportionality called resistance of the resistor. It tends to resist the flow of charge through a conducting wire. Its SI unit is ohm (Ω).