yr2-capacitance

Capacitance?

• Definition?

• Formula?

• Measured in?

• Charge stored per unit of pd (across two parallel plates)

• C = Q/V

• Measured in pico farads (pf) = 10^-12

Voltage?

• Definition?

• Formula?

Voltage is the work done per unit charge (the work done to take one coulomb from infinity to a point)

• V=wd/q

Energy stored in a capacitor?

• Formula?

Energy = ½ QV

What is a capacitor made up of?

Two parallel plates with a dielectric (insulating material) in between

When connected to a power supply, opposite charges are formed to create a uniform electric field.

What properties do dielectrics have?

Permittivity, the measure of ability of a material to store electric charge in an electric field.

Relative permittivity?

Dielectric constant which is used to measure the capacitance of a capacitor

Capacitance between two plates?

What is a dielectric?

Formed of polar molecules (it has positive and negative ends)

Energy of an isolated capacitor?

E =Q²/2C

Energy of a capacitor in a circuit ?

E =1/2 CV²

What is constant for capacitors in a circuit?

Voltage

What is constant for isolated capacitors?

Charge

What percentage does voltage, charge or current fall by when the capacitor discharges once?

37%