1. ELECTROMAGNETISM CHAPTER 18, Section 2, pages 626-631
Magnetism from Electric Currents
CHAPTER 18, Section 2, pages

2. Hans Christian Oersted
1820: Denmark
Hans Christian Oersted ?

3. I. The Discovery
1820
In the year _____, the Danish physicist ____________________ observed that:
Hans Christian Oersted
A compass needle (placed near a wire) moves as soon as current flows through the wire
B. When Oersted reversed the current direction in the conductor the compass needle…
moved in the opposite direction

4. From these observations, Oersted concluded that:
1. A current flowing through a conductor produces a magnetic field
2. The direction of this magnetic field depends on the direction of the current

5. CIRCLE II. ELECTROMAGNETISM
A. The magnetic field around a current-carrying wire forms a _________ around the conductor.
CIRCLE

7. B. The __________________ is used to find the direction of the ________________ produced by a current
RIGHT-HAND RULE
MAGNETIC FIELD
THUMB - points in the direction of the ___________
CURRENT
FINGERTIPS - point in the direction of the _______________
MAGNETIC FIELD

9. Solenoids
a __________ is a _____ of wire with an electric current in it.
SOLENOID
COIL
it acts as a _________ when current passes through it (has a ________________)
MAGNET
MAGNETIC FIELD

11. The _______________ of each loop ______ to the strength of the magnetic field of any neighboring loops.
MAGNETIC FIELD
ADDS
If the current changes direction, the ________________ changes direction and the _______ flip (use a __________ to test)
MAGNETIC FIELD
POLES
COMPASS

12. ELECTROMAGNET To INCREASE a solenoid’s magnetic field:
1. ___________________________________
Increase the # of coils (combines magnetic fields)
2. __________________________________
Increase the voltage (which increases current)
*3. __________________________________
Place ferromagnetic material in center of coils
ELECTROMAGNET
* This makes an ___________________.

13. D. ELECTROMAGNETS
Much ___________ than solenoids themselves because the magnetic field of the ______ causes the ferromagnetic core to become a ________. The _________ of the core line up and create a larger magnetic field.
STRONGER
COILS
MAGNET
DOMAINS
Ex: “magnet charger”

14. Electromagnets may be turned ______ depending on if ________ is flowing.
ON/OFF
CURRENT

15. III. ELECTROMAGNETIC DEVICES
Galvanometer/Ammeter –
Have an _________________ (attached to a pivoting needle) that interacts with a ____________ magnet to measure __________
ELECTROMAGNET
PERMANENT
CURRENT
CURRENT

16. The stronger the __________ through the coils, the greater the attraction/repulsion with the permanent magnet.
CURRENT

17. Electric Motor Motors in your house use AC
converts (changes) ____________ energy into _____________ energy (motion)
ELECTRICAL
MECHANICAL
Motors in your house use AC

19. 1. e- flow from the battery, through the _______ to the ___________ and then through the ____ of an electromagnet.
brushes
commutator
coils
DC MOTOR
Permanent magnet
Brushes
Electrons always flow in the same direction: from negative to positive.
Armature
Coil
Commutator

20. Magnetic field of the ____________ magnet interacts with the magnetic field of the _________________ (opposites _________, like poles ______)
PERMANENT
ELECTROMAGNET
ATTRACT
REPEL
3. The brushes lose contact with the “split-ring” ______________. Current is turned off, but the __________ still spins due to ________.
COMMUTATOR
ARMATURE
INERTIA

21. 4. The brushes touch the _____________ again and current flows through the coils in the __________ direction. The poles ________ and the coil repels and spins!
COMMUTATOR
OPPOSITE
SWITCH

22. Attract…repel….attract…repel….attract…repel….
5. This process continues. As current changes direction the _______________ changes direction.
MAGNETIC FIELD
Attract…repel….attract…repel….attract…repel….
the electric motor spins!