Hello academics. Can you help this student?
Your colleague tells you that the operation of a smoothing capacitor depends on its charging and discharging characteristics and these are what you should investigate. They show the results of a simple experiment in which a capacitor was connected in series with a resistor and then charged up from a DC supply. The voltage across the capacitor was measured and displayed on an oscilloscope and then compared with figures derived by calculation.
2a This is the information about the circuit:
Capacitor = 100 nF
Resistor = 47 kΩ
Supply voltage = 5 V
Charging characteristic for a series capacitive circuit:
v=V(1-e-(t/T) ) where T=CR and is called the time constant.
2b Now investigate the discharging characteristic of the circuit but with a 22 kΩ resistor fitted.
Insanity is doing the same thing you've always done and expecting different results
Your colleague tells you that the operation of a smoothing capacitor depends on its charging and discharging characteristics and these are what you should investigate. They show the results of a simple experiment in which a capacitor was connected in series with a resistor and then charged up from a DC supply. The voltage across the capacitor was measured and displayed on an oscilloscope and then compared with figures derived by calculation.
2a This is the information about the circuit:
Capacitor = 100 nF
Resistor = 47 kΩ
Supply voltage = 5 V
Charging characteristic for a series capacitive circuit:
v=V(1-e-(t/T) ) where T=CR and is called the time constant.
- Investigate what the other terms in this expression mean.
- Calculate the time constant for the circuit.
- Use a spreadsheet to plot the charging curve over the range 0 to 20 ms (milliseconds).
- Investigate the meaning of ‘time constant’ and from your graph estimate a value. Compare this with your calculated one.
- Differentiate the charging equation and find the rate of change of voltage at 6 ms.
- From your graph measure the gradient at 6 ms and compare this with the calculated value.
2b Now investigate the discharging characteristic of the circuit but with a 22 kΩ resistor fitted.
- Calculate and estimate the rate of change of voltage when t = T.
Insanity is doing the same thing you've always done and expecting different results
