Potential Differences and capacitance

Question 1

Potential differences

Answer 1

Potential difference between 2 points is the amount of work done to bring a charge of +1C from one point to the other
Unit: joule per coulomb / volt
W=QV

Question 2

Potential at a point

Answer 2

Potential differences of a point and the Earth (which has 0V)

Question 3

Capacitance

Answer 3

Ratio of the charge on the conductor to its voltage
Unit: Farad
Charge is directly proportional to voltage
Q=CV where C is a constant

Question 4

Charging a capacitor

Answer 4

Electrons from the negative side of the battery flows from the battery to the plate
Electrons that can move are attracted to the positive side of the batter and leave the plate
Charge build up between the plates so does the voltage
Movement of electrons stops when the voltage between plates and battery are equal
If battery is removed the capacitor remains charged
If 2 side of the plates are then connected by a conductor, the capacitor discharges with the electrons flowing back from the negative plates to positive plates

Question 5

E.g. of charging a capacitor

Answer 5

Smooth out variations in direct current
Camera flashlight
Variable capacitor is used to tune in stations on a radio