Electrical Quantities

Electric Current (I) definition

a base quantity usually described as the rate of flow of charged particles through a conductor and is measured in amperes

Charge

the property of matter that causes it to experience a force in an electric field, it can be positive or negative and is carried by particles, measured in coulombs

Coulomb

1 coulomb is the amount of charge which flows past a certain point in a conductor when a current of 1A flows past that point in a time of 1s

Elementary Charge

equal to the charge of an electron that is 1.6 × 10^-19 C

Potential Difference definition

the p.d. between two points in an electrical circuit is the amount of electrical energy transformed into other forms when a unit positive charge passes from one point to another

Volt

the p.d. between two points in an electrical circuit when 1J of electrical energy is transformed to other forms as 1C of charge passes from one point to another

Resistance (R)

that property of the conducting material that obstructs/hinders the flow of charged particles through through it

Ohm

the amount of resistance / a measure of resistance of a conductor when a p.d. of 1V is applied across the conductor when a current of 1A flows through it

Ohm’s Law

states that the current through an ohmic conductor is directly proportional to the p.d. across its ends provided that there is no change in the physical conditions (example temperature), i.e. V = IR (V is proportional to I)

Resistivity

a constant which relates its resistance to its length and cross-sectional area

Drift Velocity (learn to derive formula)

the speed at which the free electron moves towards the high potential (positive end) in a metal/metallic conductor when a p.d. is applied across the conductor

Electromotive Force (e.m.f.)

total energy per coulomb supplied by the power supply when there is no current in the circuit OR the terminal p.d. when the circuit is open OR total electrical energy converted to other forms per coulomb (when 1C of charge passes through the circuit)

Terminal p.d.

the p.d. across the external circuit and is usually less than the e.m.f. OR p.d. across external load (i.e. when there is a current in the circuit)

Electric Power

the rate at which electrical energy is converted to other forms