An Experiment to Determine Capacitance

The reed switch is operated from a 400 Hz supply. 

It operates on the forward half cycle, to charge up the capacitor. No current flows on the reverse half cycle so the reed switch flies back to discharge the capacitor.

We can use I = Q/t to work out the charge going onto the plates. 

We also know that f = 1/t, so we can combine the two relationships to give I = Qf, therefore Q = I/f

Since C = Q/V, we can now write C = I/fV

 

 

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