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

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

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

4. Fields caused by currents

6. The Electromagnet’s Poles The Solenoid Rule

7. 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

8. 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

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

10. What are some uses of an electromagnet? doorbell telephone motor

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

12. “Magnetic” train

13. 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.

14. Exercises

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

16. 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?

17. The dc electric motor Brush Commutator Coil (Armature)

18. 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

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