A step back…

1. A step back… Recall : All magnets have two poles (North and South) and magnetic field lines that run from North to South. ferromagnetic substances: can be induced to be magnetized. The atoms of may be thought as tiny magnets (dipoles) with a N-pole and S-pole. The more electrons that orbit the nucleus in the same direction, the more magnetic the substance. A group of atoms with the same electron spin are called domains. Un-magnetized Magnetized

2. Law of Magnetic Poles • Opposite magnetic poles attract. • Similar magnetic poles repel. Electromagnetism • Oersted discovered that moving electrons produce a magnetic field around the conducting wire • Right Hand Rule For Conductors Hold conductor in the right hand, thumb pointing in the direction of current, curled fingers point in direction of magnetic field lines.

3. Draw the field lines

4. 12.4 Solenoids

5. Ampere’s Experiment • Two wires side by side with current flowing in opposite directions. • Force pushes wires apart • Overall magnetic field

6. Solenoid • A coiled conductor Right Hand Rule for a Solenoid Fingers= current Thumb = magnetic field (N)

7. Properties of Solenoids • Solenoids can act as very powerful magnets that can be switched on and off. (Electromagnet) • To increase the magnetic field • a) increase number of loops • b) increase current • c) use a soft iron core inside the solenoid • Subwoofer, school bell, industrial crane magnets etc…

8. Homework: • Pg 562 #’s 1-7