Experiment Description

Experiment

Experiment E05    Measuring Time Constant for Charging and Discharging Circuits

Objectives
  • Investigate the charging and discharging processes of a capacitor
  • Study the exponential variation of voltage across a discharging capacitor
  • Study the capacitive time constant through the charging and discharging circuits
  • Measure the capacitive time constant from the ln(V) - t graph
Description
In this activity, you will use a CRO to measure the voltage change as the capacitor is charged and discharged slowly via a high resistance (100 kohm). Using a stop watch, you will record the time variation of the voltage and plot a graph of V against time.

In Experiment 1, you will study the discharging process of a capacitor using a CRO. As the capacitor discharges, the voltage is recorded in regular time interval until it falls to zero.

In Experiment 2, you will charge the capacitor through the high resistance. The flying lead is to discharge the capacitor completely before charging it. After the switch S is closed, the charging process starts.
Apparatus
capacitor (470 mF) [1]
resistor (100 kOhm) [1]
battery box with 4 dry cells [1]
switch [1]
stop watch [1]
single beam CRO [1]
capacitor (1000 mF) [1]
resistor (47 kOhm) [1]
Experiment