Capacitor charging and discharging teaching demonstration

How does an uncharged capacitor work?

In figure (a), an uncharged capacitor has been illustrated, because the same number of free electrons exists on plates A and B. When a switch is closed, as has been shown in figure (b), then the source, moves electrons towards B via the circuit. In this way, the flow of electrons starts from plate A, and electrons start to store on plate B.

How can students see the pattern of potential difference between capacitors?

Students can use an iterative approach, with the help of a spreadsheet, to see the pattern of potential difference across the capacitor while it is discharging (top graph), and charging (bottom graph). Episode 129-2: One step at a time (Word, 33 KB)

What happens when a capacitor is fully charged?

When a capacitor gets fully charged, the value of the current then becomes zero. Figure 6.47; Charging a capacitor When a charged capacitor is dissociated from the DC charge, as has been shown in figure (d), then it remains charged for a very long period of time (depending on the leakage resistance), and one feels an intense shock if touched.

Why does a capacitor not change when charged or discharged?

When a capacitor is either charged or discharged through resistance, it requires a specific amount of time to get fully charged or fully discharged. That’s the reason, voltages found across a capacitor do not change immediately (because charge requires a specific time for movement from one point to another point).

Can the experiment be repeated with different capacitors?

The experiment can be repeated with different capacitors. Plot a graph of Q against V. Episode 126-2: Measuring the charge on a capacitor (Word, 47 KB) The second investigation of the relationship between charge and pd makes use of a change-over reed switch. Students may have met simple on/off reed switches in technology or even in primary school.

Why does a capacitor require a certain amount of time?

Because, resistance introduces an element of time during the charging or discharging of a capacitor (that’s by means of resistance, a charged capacitor will require a certain amount of time for getting discharged).