State with the help of a circuit diagram an activity to find the resistance $R$ of a given wire. $A$ current of $0.2 \, A$ passes through a resistor of $20 \, \Omega$. Find the potential difference across its ends.

(N/A) The circuit diagram is as shown in the image.
Activity to find the resistance $R$:
$1$. Set up a circuit using the wire of resistance $R$,an ammeter,a voltmeter,a plug key,and four cells of $1.5 \, V$ each.
$2$. First,use one cell as the source and note the readings of the ammeter $(I)$ and voltmeter $(V)$.
$3$. Increase the number of cells one by one and note the corresponding readings of $I$ and $V$.
$4$. Calculate the ratio $V/I$ for each set of readings. The average of these ratios gives the resistance $R$ of the wire.
Numerical calculation:
Given: Current $(I) = 0.2 \, A$,Resistance $(R) = 20 \, \Omega$.
Using Ohm's Law: $V = I \times R$
$V = 0.2 \, A \times 20 \, \Omega = 4 \, V$.
Thus,the potential difference across the ends of the resistor is $4 \, V$.