This problem6 illustrates how a digital voltmeter affects the voltage across a capacitor in an RC circuit. A digital voltmeter of internal resistance r is used to measure the voltage across a capacitor after the switch in Figure P28.76 is closed. Because the meter has finite resistance, part of the current supplied by the battery passes through the meter.
(a) Apply Kirchhoff€™s rules to this circuit, and use the fact that iC = dq/dt to show that this leads to the differential equation where Req = rR/(r % R).
(b) Show that the solution to this differential equation is After Joseph Priest, "Meter Resistance: Don't Forget It!" The Physics Teacher, January 2003, p. 40. and that the voltage across the capacitor as a function of time is
(c) What If? If the capacitor is fully charged, and the switch is then opened, how does the voltage across the capacitor behave in this case?

Transcribed Image Text:

r+ R + 오 =- Voltmeter