Practice question · Numerical answer
A capacitor discharges through a resistor with a time constant of 2.0 s. What percentage of the initial voltage remains after 2.0 s? Give the answer to the nearest whole number.
Hints
- After exactly one time constant the voltage has fallen by a factor of e.
- Compute 100 divided by e, roughly 2.718.
Show the answer
37 (answers within ±1.5 count)
Why
After one time constant , so about 37 % remains. This is the definition of the time constant, and it is why can be read straight off a decay trace.
Practise Electromagnetic Measurement
The app has 5 more questions on this lesson, and keeps your place in the course. Physics II is free to start.
More questions on Electromagnetic Measurement
- Why must a voltmeter have a very high internal resistance?
- Two independent uncertainties of 0.3 and 0.4 units combine in quadrature. Compute the combined uncertainty,…
- Extracting the RC decay constant from the gradient of a ln V versus t plot is preferred over recording the…
- A current meter must carry the full current and add almost no resistance.
- Which practices are sound experimental technique?
- Averaging repeated measurements reduces random error but not systematic error.