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Best time interval for measuring capacitor discharge?

  • #1

Homework Statement


My (practise) coursework is to test the equation 'V = Vo e-t/RC' and choose values of R and C so that the voltage across the capacitor falls to half in 15 seconds. I decided it would be too difficult and inaccurate to record the voltage across the capacitor every 5 seconds, so I chose 10. However, I'm not sure if this will get me enough readings.

Homework Equations


V = Vo e-t/RC

The Attempt at a Solution


I decided it would be too difficult and inaccurate to record the voltage across the capacitor every 5 seconds, plus having a small time interval would give a larger percentage error, so I chose 10. However, I'm not sure if this will get me enough readings if the voltage is going to halve in 15 seconds. However, I know the rate of discharge will decrease, so it may be suitable anyway. Does anyone have any suggestions?
 

Answers and Replies

  • #2
.Scott
Homework Helper
2,414
832
Suggestion 1: Use a digital oscilloscope.
Suggestion 2: Repeat the experiment three times. In each case, wait for the voltage to dip below some voltage - say 5.00 - before starting the timer. Then catch the voltage at 5 seconds, 20 seconds, 35 seconds, and 50 seconds on the first try. Then at 10 seconds, 25 seconds, 40 seconds, and 55 seconds on the seconds try. Then 15 seconds, 30 seconds, 46 seconds, and 60 seconds on the third try. That will give you zero to 60 seconds in 5 second intervals and 15 seconds to make each recording.
 
  • #3
Suggestion 1: Use a digital oscilloscope.
Suggestion 2: Repeat the experiment three times. In each case, wait for the voltage to dip below some voltage - say 5.00 - before starting the timer. Then catch the voltage at 5 seconds, 20 seconds, 35 seconds, and 50 seconds on the first try. Then at 10 seconds, 25 seconds, 40 seconds, and 55 seconds on the seconds try. Then 15 seconds, 30 seconds, 46 seconds, and 60 seconds on the third try. That will give you zero to 60 seconds in 5 second intervals and 15 seconds to make each recording.
That's a really clever idea, thank you! I'll definitely try that tomorrow.
 

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