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The experiment requires four cells of $$1.5\ V$$, $$0.5\ m) coil of nichrome wire, key, ammeter, and voltmeter. Nichrome is an alloy of nickel, chromium, manganese, and iron metals. Experimental set-up • Connect the cell, nichrome wire, ammeter and key in series, and the voltmeter parallel to the circuit. • First, connect only one cell in the circuit. • Note down the current value in the ammeter and the potential difference across the nichrome wire \(XY$$ in the voltmeter.
• Now, connect two cells in the circuit.
• Note down the current value in the ammeter and the potential difference across the nichrome wire $$XY$$ in the voltmeter.
• Again, connect three cells in the circuit and note the current and the potential difference.
• Repeat the same steps using four cells in the circuit.
• Tabulate the values of current ($$I$$) and the potential difference ($$V$$) as shown in the table.
 S.No No. of cells used in the circuit Current ($$I$$) through the nichrome wire ($$ampere$$) Potential difference ($$V$$) across the nichrome wire ($$volt$$) Resistance$$=$$ $$\frac {V}{I}$$ (Ohm) 1. 1 2. 2 3. 3 4. 4

Graphical representation:
From the values obtained, it is observed that the values of $$\frac {V}{I}$$ are the same. The graph between the potential difference ($$V$$) and the current ($$I$$) is a straight-line for a conductor since $$V$$ is proportional to $$I$$. The line proves that $$\frac {V}{I}$$ is a constant ratio.

The relation between potential difference and current

The straight-line shows that as the current through a metallic wire increases, the potential difference across the wire also increases linearly.