Physics Experiments

To investigate the variation of current ($I$) with P.D. ($V$) for (a) a metallic conductor

Apparatus

Low voltage power supply, rheostat, voltmeter, ammeter, length of nichrome wire.

Procedure

• Set up the circuit as shown and set the voltage supply at 6V d.c.
• Adjust the potential divider to obtain different values for the voltage $V$ and hence for the current $I$.
• Obtain at least six values for $V$ and $I$ using the voltmeter and the ammeter.
• Plot a graph of $I$ against $V$.

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To investigate the variation of current ($I$) with P.D. ($V$) for (a) a metallic conductor

Results

$V$/V	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5
$I$/mA

Conclusion

A straight line through the origin ⇒ $I ∝ V$

Notes

A varying voltage can be obtained from a fixed supply voltage by using a potential divider. It consists of a variable resistor or fixed resistors in series. Move the slider to change the output voltage. This results in the output voltage from the potential divider being a fraction of the input voltage.

The value of R may be determined from the reciprocal of the slope of the graph.

1 m of 26 s.w.g. nichrome wire, wound on a plastic comb, may be used in this experiment. This has a resistance of approximately 7.0 Ω.