Electromagnetism

describe the construction of electromagnets

• wrapping insulated copper wire into a coil

• around a magnetically soft core

• and passing an electric current through wire

what is the Motor Effect?

• current carrying wire generates magnetic field

• that field interacts with the external (other) magnetic field

• this results in a force on wire, at right angles to the current + external field

how does a DC motor work? [3 bullet points]

• split-ring commutator ensures current always flows same way around loop

• means forces on each side of loop = always opposite each other

• means loop keeps rotating in same direction (clockwise)

how does a loudspeaker work? [3 bullet points]

• interaction between external magnetic field + current-carrying coil causes a force to be exerted on cone

• bc sound wave represented by AC, force keeps changing direction

• therefore cone vibrates

what affects the magnitude of the force?

• magnetic field strength (B)

• current (I)

• angle between field + current - force biggest at 90

• field + current are parallel = no force