6.1 Capacitors

Question 1

What are capacitors?

Answer 1

Capacitors are electrical components in which charge is separated.
It consists of two metallic plates separated from each other by a dielectric, which is an insulator, such as air, paper, ceramic

Question 2

What is a dielectric?

Answer 2

A dielectric is an insulator such as air, paper or ceramic, that is placed in between the two metallic plates of a capacitor to prevent charge from flowing across the gap

Question 3

Explain how charge is stored in a capacitor

Answer 3

• When a capacitor is connected to a cell of electromotive force, the electrons flow from the cell for a very short time
• The electrons cannot travel between the plates of the capacitor because of the insulation
• The very brief current means that electrons are removed from plate A of the capacitor, and at the same time electrons are deposited onto plate B of the capacitor
• Plate A becomes deficient in electrons and so it aquires a net positive charge
• Plate B gains electrons and hence becomes negatively charged
• As current in the circuit must be the same at all points, and charge must be conserved, the two plates have an equal but opposite charge of magnitude Q.

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Question 4

Define Capacitance

Answer 4

The capacitance of a capacitor is defined at the charge stored per unit potential difference across it

Question 5

The greater the capacitance…

Answer 5

The greater the capacitance, the greater the charge stored in the capacitor