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

Hans Christian Oersted 1820: Denmark Hans Christian Oersted ?

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

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

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

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

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

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

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 ___________________.

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”

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

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

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

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

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

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

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

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!