Level 2 NCEA Physics Electricity

Unlike charges

negative potential energy (attractive force). Unlike charges attract.

Like charges

positive potential energy (repulsive force). Like charges repel.

Attraction of Electric Charges

Opposite charges pull toward each other.

Repulsion of Electric Charges

Like charges push away from each other.

Charging by Conduction

Contact with an already charged object.

Charging by Friction

Rubbing transfers charge (one +, one –).

Charging by Induction

Charging without contact (proximity effect).

Electrostatic charge

Accumulated electric charge due to electron surplus/deficiency.

Conductors

Materials that allow charges to flow easily.

Insulators

Materials that obstruct charge flow.

Resistors

Objects that reduce charge flow (convert to heat/light).

Electrical Conductors

Metals (free-moving electrons).

Electrical Insulators

Block flow of electricity.

Electrolyte

Ionic solution conducting current.

Superconductors

Resistance nearly zero under certain conditions.

Current (Electricity)

Flow of electrons through a conductor.

Direct Current (DC)

Current always flows in one direction.

Electron Current

Flow from negative to positive terminal.

Electric Circuit

Voltage source + continuous conducting path.

Simple Circuit

Only one pathway for electricity.

Series Circuit

Current flows through each component in turn.

Solenoid

Cylindrical coil of wire; becomes electromagnet with current.

Electromagnet

Magnet formed by solenoid; on/off with current.

Electric Generator

Wire loops in magnetic field generate electricity.

Electric Field

Region around a charge exerting force.

Electric Field Lines

Show force direction on a positive charge.

Electric Flux

Surface area × perpendicular electric field component.

Electric Potential

Difference in charge (voltage).

Electric Potential Energy

Energy due to charge position relative to others.

Electrical Force

Fundamental force from charge interaction.

Electromagnetic Force

One of the four fundamental forces.

Electromagnetic Induction

Inducing current by moving a wire in a magnetic field.

Magnetic Dipole

Magnet with north & south poles (cutting makes 2 dipoles).

Magnetic Poles

Ends of a magnet where force is strongest.

Magnetic Field Lines

Map magnetic field direction.

Magnetic Flux

Number of magnetic field lines through a surface.

Magnetic Forces

Attraction/repulsion without contact.

Magnetism

Force of attraction/repulsion between poles.

Magnetic Reversal

Flipping of Earth’s magnetic polarity.

Ferromagnetic Materials

Iron, cobalt, nickel.

Coulomb (C)

Unit of electric charge.

Ohm (Ω)

Unit of resistance (V/A).

Ohm’s Law

$$R = \frac{V}{I}$$

Resistance

Opposition to current flow (measured in ohms).

Power

Rate of doing work. $P=IV=I^2R=\frac{V^2}{R}$

Voltage Drop

Potential difference across a resistor or component.