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The following is part of a student's report on an experiment to investigate the variation of the current I with potential difference V for a semiconductor diode - Leaving Cert Physics - Question 4 - 2012
Question 4
The following is part of a student's report on an experiment to investigate the variation of the current I with potential difference V for a semiconductor diode. "I... show full transcript
Worked Solution & Example Answer:The following is part of a student's report on an experiment to investigate the variation of the current I with potential difference V for a semiconductor diode - Leaving Cert Physics - Question 4 - 2012
Step 1
Draw a circuit diagram used by the student.
Answer
To draw a circuit diagram for the investigated current-voltage relationship of a semiconductor diode, include:
- Apparatus: A diode, ammeter, voltmeter, and a variable resistor.
- Correct Arrangement: The diode should be in the forward bias configuration.
- Connections: The ammeter must be in series with the diode, while the voltmeter should be connected across the diode to measure the potential difference.
Ensure that all components are clearly labeled in your diagram.
Step 2
How did the student vary and measure the potential difference?
Answer
The student varied the potential difference by adjusting the variable resistor in the circuit. The variable resistor allows for control of the current and voltage supplied to the diode, thus changing the potential difference across it.
To measure the potential difference, the student connected a voltmeter across the diode. This setup ensures that the voltmeter readings reflect the potential difference while the current flows through the diode.
Step 3
Using the data, draw a graph to show how the current varies with the potential difference for the semiconductor diode.
Answer
To graph the relationship between current and potential difference:
- Label the Axes: The x-axis should represent the potential difference (V) and the y-axis should represent the current (I).
- Plot Points: Use the recorded data to plot points corresponding to voltage and the current values.
- Draw the Curve: After plotting, connect the points smoothly to illustrate how the current increases as the potential difference increases, typically following an exponential curve for diodes.
Step 4
Does the resistance of the diode remain constant during the investigation? Justify your answer.
Answer
The resistance of the diode does not remain constant during the investigation.
In a diode, resistance changes with voltage due to its non-linear characteristics. As the potential difference increases, the current also increases at a faster rate, indicating that the diode’s resistance decreases as it enters forward conduction. According to Ohm's Law: As V increases while I increases more rapidly, R varies according to the changing conditions, illustrating that the diode does not have a constant resistance throughout the experiment.
Step 5
What adjustments should be made to the circuit to obtain valid readings?
Answer
To obtain valid readings with the connections to the semiconductor diode reversed, consider the following adjustments:
- Reconnect the Diode: Ensure that the diode is connected in the correct orientation for forward bias operation.
- Use Correct Measurement Instruments: Make sure the ammeter is in series and the voltmeter is in parallel, as per standard practices for measuring current and voltage, respectively.
- Component Ratings: Verify that the components, especially the diode and multimeter, are suitable for the expected voltage and current levels to prevent damage or incorrect readings.