Question

(a) What is the ratio of potential difference and current known as?
(b) The values of potential difference V applies across a resistor and the corresponding values of current I flowing in the resistor are given below:

Potential differences, V (in volts)	:	2.5	5.0	10.0	15.0	20.0	25.0
Current, I (in amperes)	:	0.1	0.2	0.4	0.6	0.8	1.0

Plot a graph between V and I, and calculate the resistance of the resistor.
(c) Name the law which is illustrated by the above V−I graph.
(d) Write down the formula which states the relation between potential difference, current and resistance.
(e) The potential difference between the terminals of an electric iron is 240 V and the current is 5.0 A. What is the resistance of the electric iron?

Answer 1

(a) The ratio of potential difference and current is known as resistance R.
(b)

From the graph, resistance, R =$\frac{V}{I}=\frac{5}{0.2}=25\mathrm{\Omega }$

(c) Ohm's law is illustrated by the above V−I graph.

(d)Relation between potential difference and current is
V = IR

(e) The potential difference between the terminals of an electric iron is 240 V and the current is 5.0 A.
So resistance $\mathrm{R}=\frac{V}{I}=\frac{240}{5}=48\mathrm{\Omega }$
Thus, the resistance of the electric iron will be 48 Ω.