Electricity and Magnetism

Electric Current (I)

Flow of charge (electrons) in a fixed direction.

• Measured in Amperes (A)

• Only measured in a series circuit

Static Electric Current

A current that does not move/flow.

Electric Charge (C)

Imbalance in the number of protons and electrons.

* Measured in coulombs (C)

Voltage (V)

When one joule of energy is given to one coulomb.

* V= E/Q(C)

Electron Pumps

‘Pump’ electrons by pulling them from one end of a wire and pushing them into the other.

• Convert chemical energy to electricity.

• (E.g: Cells/batteries)

Cell

Transfers energy to electrons.

Battery

Two or more cells.

Conductor

Materials that allow electrons to pass through them well.

* (E.g: Metals have free electrons between atoms, making them great conductors)

Insulator

Materials that do not allow electrons to pass through them well.

* (E.g: Rubber has tightly bound electrons)

Semi-Conductor

Materials that are neither conductors nor insulators.

* (E.g silicon and germanium are good conductors when warm, poor when cold)

Electric Circuit

A continuous path of wires and electrical components where electrons can flow. Controlled by a switch between two terminals of a cell or battery.

Series Circuit

A circuit with only one electric current flows throughout.

* I₁ = I₂ = I₃ = I₄

Parallel Circuit

A circuit in which the current is split to power two or more electrical components.

• The voltage of each branch is the same, but the currents may vary

• IT = I₁ + I₂ + I₃ + I₄

When more bulbs are added in a series circuit, the brightness_____.

Dims

* The current is split across each bulb and grows weaker.

When more bulbs are added in a parallel circuit, the brightness ______.

Stays the same

* The current is split evenly across each bulb.

Electric Resistance (R)

When a current experiences opposition as it passes through a material cue to collisions of the electrons.

* Measured in ohms (Ω)

Resistors

Materials that oppose/resist the flow of electric currents.

Insulators have _______ resistance.

Infinite

Conductors have _______ resistance.

Near-zero

Semi-conductors have _______ resistance.

Some

Resistors have _______ resistance.

Finite