6 Capacitors

What is the structure of a capacitor

It consists of two metal plates seperated by a thin layer of insulating material called a dielectric.

What is the formula for capacitance

C = Q/V

What affects the capacitance

The area of the metal plates, the distance separating the metal plates, material used for the dielectric

What types if non-polarised capacitors are there

mica, ceramic, polyester film

What type of polarised capacitors are there

aluminium electrolytic, tantalum electrolytic

What are the differences between a polarised and non-polarised capacitors

Non-polarised capacitors can be connected in any direction but have smaller capacitances and are typically smaller

Why is it important to use a capacitor with care?

Without a discharge path, a capacitor can hold onto electric charges for a long time and may endger the person working on the circuit, especially if it is charged to a high voltage.

What affects the charging and discharging of a capacitor?

The resistance and the capacitance of the capacitor

Formula for time constant

t = RC

What is the significance of the time constant?

It is the amount of time to get to 2/3 of the applied voltage and 5t is when it is charged to 99.3%

What happens when you short circuit a capacitor

It creates a large current spike that may damage the capacitor

How do you discharge a capacitor corre

Connect a resistor between the two metal plates

Describe what happens when the switch in an RC circuit is closed.

The capacitor starts to be charged and the voltage across it increases. This continues until Vc equals to the emf.

Describe a charging graph

The graph is non-linear. Vc increases rapidly at first but slows down as it reaches the applied voltage

If a mica resistor has 473 on its, what is its capacitance?

47 000 pF