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11.3 Capacitance
11. Electromagnetic induction
Investigating charging and discharging a real capacitor
“
A capacitor is a device that stores electrical energy in an electric fi eld. It is a passive electronic
component with two terminals.
”
Source:
https://en.wikipedia.org/wiki/Capacitor
Equipment: required: DC supply (less than maximum voltage of capacitor), connecting wires,
Pasco Wireless voltage sensor, device running SparkVue, various capacitors, various resistors.
Filament lamp (voltage similar to that of the supply).
Experiment 1: Discharging a capacitor.
Method
1.
Connect the capacitor to the DC supply.
2.
The voltage of the supply should be less than that of the capacitor.
3.
Disconnect and connect to a lamp.
4.
Observe the effect of the capacitor-lamp circuit.
5.
Write down these observations below.
6.
What are the implications of this observation on your understanding of a capacitor.
Write what you see and what this means here:
Experiment 2: Charging a capacitor
Method
1.
Connect the wireless voltmeter to your device.
2.
Connect the voltmeter in parallel to the capacitor.
3.
Connect the DC supply to the capacitor and observe the V-t graph. Sketch below
4.
Add a resistor in series to the capacitor and record the value (use
https://www.calculator.net/
resistor-calculator.html
).
5.
Sketch the V-t graphs of what you have observed.
6.
Repeat with another resistance with greater resistance.
7.
What affect does the resistor have on the charging of the capacitor?
11.3 Capacitance
11. Electromagnetic induction
Experiment 3: Discharging a capacitor
Method:
1.
Connect the wireless voltmeter to your device.
2.
This time charge the capacitor with the source before disconnecting it from the source.
3.
Connect the voltmeter in parallel to the capacitor
and observe the V-t graph. Sketch below
4.
Add a resistor in series with the capacitor and record the value (use
https://
www.calculator.net/resistor-calculator.html
).
5.
Repeat with another resistor with greater resistance.
6.
What affect does the resistor have on discharging of the capacitor?
Experiment 4: Detailed analysis of the discharge of a capacitor
Method
1.
For the most recent experiment above, export the data to excel or another spreadsheet.
2.
Add a line of best fi t.
3.
Determine the gradient of the line.
4.
Replot as a straight line.
5.
What does the y-intercept and the gradient correspond to?
