Chap 19: Physics-Static electricity

Coulomb’s law

States that the forces between two point charges is proportional to the product of the charges and inversely proportional the square of the distance between them.

Electric field strength

Force per unit charge

Potential difference

Is the work done in moving a charge of one Coulomb from one point to another.

Capacitance of a conductor

Is the ratio of the charge on the conductor to it’s potential

Potential difference between two points

Is one Volt if one Joule of work is done when bringing a charge of one coulomb from one point to another

Point discharge

1.) Charge accumulates at a point

2.) Air around point is ionised

3.)Opposite charges attract/ like charges repel

electric current

a flow of charge

Voltage

when applied to a circuit is an emf

Resistance of a conductor

the ratio of the potential difference across the conductor to the current flowing through it.

Ohm’s law

states that the current flowing through the conductor is directly proportional to the potential difference across it, assuming constant temperature.

Resistivity

the resistance of a cube of material of side one metre.

the kilo-watt

is the amount of energy used by a 1000 Watt appliance in one hour.

Joules Law

states that the rate at which heat is produced in a conductor is proportional to the square of the current, provided its resistance is constant.

The ampere

is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible cross section and placed 1 metre apart in a vacuum, would produce a force on each conductor of 2×10^-7 newtons per metre of length.

The coulomb

the amount of charge that passes any point in a circuit when a current of 1 ampere flows for 1 second.

The Volt

The potential difference between two points is 1 volt if 1 joule of work is done when 1 coulomb is brought from one point to the other. 1V = 1J C^-1