Required Practical Activity 4 Flashcards
Circuit diagram to find I-V characteristics of filament lamp:
Method to find I-V characteristics of filament lamp:
- Set up apparatus as shown in circuit diagram above
- Change reading on variable resistor until potential difference across filament bulb is -10V (measure the potential difference across the filament bulb using the voltmeter)
- Measure current using ammeter connected in series to circuit while potential difference across bulb is -10V
- Repeat the experiment but continue to change the reading on the variable resistor until potential difference on voltmeter across the filament bulb in increments of 1V up to 10V
- Plot graph of results with potential difference on x-axis and current on the y-axis
Graph of current and potential difference of a filament lamp:
How do you improve the accuracy when finding the I-V characteristics of a filament bulb?
- Use the same components for each repeat
- Do not just use the same value of component as they may be slightly different from one another
- Use a low currentand turn the circuit off between readings - this prevents the wires and components increasing in temperature which would increase resistance and affect future readings including repeat readings
What are the results for the I-V characteristics of a filament bulb?
- As potential difference increases, current increases
- At small potential differences the relationship between potential difference and current is linear (the gradient is constant)
- At large potential differences the gradient becomes more shallow as the resistance of the bulb increases due to a higher temperature in the circuit
Explain the results for the I-V characteristics of a filament bulb:
- At small potential differences there is a small current so the heating effect of the current is small and the filament remains at a low temperature
- At large potential differences there is a large electrical current so the heating effect of the current is large which causes the filament to be a high temperature
- This is caused by electrons in the wire colliding with ions in the metal lattice causing them to vibrate
- Wires (like the filament) have a greater resistance at higher temperatures, causing the increase in current to be reduced
- This is because the more the ions in the metal lattice vibrate the more likely electrons are to collide with
them and slow down
Circuit diagram to find I-V characteristics of a diode:
Method to find I-V characteristics of a diode:
- Set up apparatus as shown in circuit diagram above
- Change reading on variable resistor until potential difference across diode is -10V (measure the potential difference across the diode using the voltmeter)
- Measure current using ammeter connected in series to circuit while potential difference across diode is -10V
- Repeat the experiment but continue to change the reading on the variable resistor until potential difference on voltmeter across the diode in increments of 1V up to 10V
- Plot graph of results with potential difference on x-axis and current on the y-axis
Graph of current and potential difference of a diode:
How do you improve the accuracy when finding the I-V characteristics of a diode?
- Use the same components for each repeat
- Do not just use the same value of component as they may be slightly different from one another
- Use a low current and turn the circuit off between readings
- This prevents the wires and components increasing in temperature which would increase resistance and affect future readings including repeat readings
What are the results for the I-V characteristics of a diode?
- For a positive potential difference the current increases rapidly with an increase in potential difference
- For a negative potential differencethe current remains negligible and does not increase as the potential difference becomes larger
What is the explanation behind the I-V characteristics of a diode?
The resistance of a diode is very low for current in the forward direction and very high in the back direction
Circuit diagram to find I-V characteristics of a resistor:
Method to find IV characteristics of a resistor:
- Set up apparatus as shown in circuit diagram above
- Change reading on variable resistor until potential difference across diode is -10V (measure the potential difference across the resistor using the voltmeter)
- Measure current using ammeter connected in series to circuit while potential difference across the resistor is -10V
(reverse the polarity of an electrical circuit, you can switch the connections of the positive and negative terminals of the power supply or battery)
- Repeat the experiment but continue to change the reading on the variable resistor until potential difference on voltmeter across the resistor in increments of 1V up to 10V
- Plot graph of results with potential difference on x-axis and current on the y-axis
Graph of current and potential difference across a resistor:
