P4: Electricity and magnetism

magnetism

a force that can attract and repel objects without touching them

magnet

object that produce a magnetic field

direction of magnetic field

the direction of the force on the N pole of a magnet at that point

electric field

a region of space in which an electric charge experiences a force

direction of an electric field

the direction of the force on a positive charge at that point

conductor

material that allows charges flow through easily

insulator

material that has no free charge, hence does not allow the flow of charge through it easily

electric current

the charge passing a point per unit time

direct current

a steady current, constantly flowing in the same direction from positive to negative

alternating current

a curent that continously changes ít direction, going back and forth around a circuit

emf

the electrical work done by a source in moving a unit charge around a complete circuit

pd

work done by a unit charge passing between two points in a circuit

transformer

a device that changes the voltage of an AC

dípersion

white light splits into its constituent colors when it passes through a glass prism

principal axis

a straight line passing thoruhg the center of the lens and perpendicular to the surface

focal point (principal focus)

point where light converge after passing through the lens

focal length

the distance from the centre of the lens to its principal focus