To investigate the variation of current (I) with P.D. (V) for (d) semiconductor diode

Apparatus

Low voltage power supply, rheostat, voltmeter, milliammeter, 330 Ω resistor, silicon diode, e.g. 1N4001.

Procedure - Forward Bias

• Set up the circuit with the semiconductor diode in forward bias as shown and set the voltage supply to 9 V.
• Adjust the potential divider to obtain different values for the voltage V and hence for the current I.
• Obtain at least ten values for V and for I using the voltmeter and the milliammeter.
• Plot a graph of I against V and join the points in a smooth, continuous curve.

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To investigate the variation of current ($I$) with P.D. ($V$) for (d) semiconductor diode

Results – Forward Bias

$V/$ V	0.1	0.2	0.4	0.45	0.5	0.55	0.6	0.62	0.64	0.66	0.68	0.70
$I/$mA

Notes

Almost no current flows until the applied voltage exceeds 0.6 V for a silicon diode but then the current rises rapidly.

A germanium diode, e.g. OA91, gives very little current between 0 and 0.2 V but the current then increases above this voltage.

A light emitting diode gives very little current up to 1.6 V but then the current rises rapidly accompanied by the emission of light.