Basics in Magnetism Electromagnetism Force on a Current-Carrying Wire EM Induction Transformer Generators Electric Motors ELECTROMAGNETISM

The Electromagnets  What did Hans Oersted discover in 1820?  What are some uses of electromagnets?  What factors affect the strength of an electromagnet?

What did Hans Oersted discover in 1820? Electricity could cause magnetic effects! Electromagnet

Fields caused by currents

The Electromagnet’s Poles The Solenoid Rule

What factors affect the strength of an electromagnet? The size of the iron core The number of turns of wire The number of turns of wire The voltage of battery Bigger size, greater strength More turns, greater strength Higher voltage, greater strength

What other factors affect the characteristics of the electromagnet? The polarity of source Type of Source (AC or DC) Changes direction of magnetic field AC has changing magnetic field DC has same magnetic field

Use of e-magnet: The magnetic relay Symbol for relay How a relay works Simple circuit with a relay

What are some uses of an electromagnet? doorbell telephone motor

What are some uses of an electromagnet? Crane’s magnet Crane’s magnet MRI bullet train

“Magnetic” train

What happens when you put a current- carrying wire in a magnetic field? The wire experiences a force from the magnet! Beam of electrons in a magnetic field. Fleming’s Left-hand Rule Magnetic force will only exist when the current is perpendicular to the magnetic field.

Exercises

Force on a loop of wire NS Current Force The loop will turn anticlockwise Top view Side view A B A B

Force on a loop of wire NS Current Force The loop will turn in reverse (clockwise) Top view Side view A B A B How do we keep the loop turning in the same direction?

The dc electric motor Brush Commutator Coil (Armature)

What factors affect the force on the coil? The strength of magnet The number of turns of wire The number of turns of wire The voltage of battery Greater strength, greater force More turns, greater force Higher voltage, greater force

Uses of the electric motor Washing Machine Clock Fan HDD Toothbrush Meter