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igcse physics notesprinted 106 · PDF 106
124 pagesrevision 46936
printed 106 · PDF 106
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106
Increasing the speed of rotation
An electric current passing through a conductor produces a magnetic field
around it. An electromagnet is a coil of wire wrapped around a solenoid
with a soft iron core that acts as a magnet when current flows through it
and can be turned on and off.
AC generator
In direct current, current flows in one direction only while in alternating
current, the current continuously changes direction.
It consists of a coil of wire between two permanent magnets. They
generate AC current because a slip ring commutator is used.
Slip ring commutator is used to reverse the direction of current after every
half rotation.
As the coil rotates magnetic flux changes and emf is induced.
The magnitude of emf is maximum when coil is horizontal as the field lines
are cut fastest, and zero when coil is vertical because no field lines are cut.