Charging And Discharging Pg 134

Question 1

Give three expressions for the energy stored by a capacitor

Answer 1

E equals half Q V

E equals half C Vsquared

E equals 1/2Q^2/C

Question 2

How can you investigate what happens when you charge a capacitor

When the current through the ammeter is zero…

Answer 2

You need a high resistance resistor 
a capacitor
 a DC power supply
 an Ammeter
 a voltmeter
 a data logger  
and a computer

Close the switch to connect the uncharged capacitor to the DC power supply

Let the capacitor charge whilst the datalogger records both the potential difference from the volt meter and the current from the ammeter over time

When the current though the ammeter is zero ,the capacitor is fully charged

Question 3

As soon as the switch closes… Starts to flow

The electrons flow onto the plate connected to the negative terminal of the DC power supply so a…

This buildup of negative charge… Electrons off the plate connected to the positive terminal of the power supply, making that plate…
These electrons are attracted to the… Of the power supply

And equal but opposite charge builds up on… Causing a…Between the plates. Remember that no charge can flow between the plates because…

As the charge builds up on the plates, electrostatic repulsion makes it… And… Or more electrons to be…
When the potential difference across the capacitor is equal to the potential difference across the power supply the…

Answer 3

Current

A negative charge builds up

Repels

Positive

Positive terminal

Each plate

Potential difference between the plates

They are separated by an insulator (a vacuum ,gap or dielectric)

Harder
Harder

Deposited

The current falls to zero

Question 4

To discharge a capacitor,..

Answer 4

Remove the power supply and close the switch