Electricity & Magnetism

Magnets are Cool Watch this video until 0:35. What happens to the sliding magnet when the system is turned upside down? It is launched at high speed It falls at 9.81 m/s2 It does not move It falls toward the other magnets

Magnetic Fields We say that magnets are surrounded by a magnetic field of force exiting the magnet at one end, and re-entering at the other end. We can sense these fields with ferromagnetic materials (e.g. iron filings) or other magnets (compasses). Watch This Video

Magnetic Fields The shape and direction of the field around a magnet is determined using a compass.

Magnetic Fields

Magnetic Field Lines

Magnetic Field Lines Properties of magnetic field lines: Outside the magnet, point from north to south. Inside the magnet, point from south to north. Never cross. Are denser when the magnetic field is stronger (i.e. the more closely spaced the lines, the greater the force.)

Magnetic Field Around the Earth

Magnetic Field Lines

Magnetic Force Law of Magnetic Forces: 1. Opposite poles attract

Magnetic Force Law of Magnetic Forces: 2. Similar poles repel

Magnetic Force Law of Magnetic Forces: 3. Force varies inversely as the square of the distance between the poles. Distance Force 1.0 m 100 N 2.0 m 5.0 m × 2 × ?

Magnetic Field Lines Magnetic field around a bar magnet Magnetic field between a pair of opposite poles

Magnetic Domains What happens if you break a magnet in half? Each piece will always have a north-seeking pole and a south-seeking pole. For this reason, magnets are called dipoles. In contrast, electric charges are known as monopoles.

Magnetism What happens to permanent magnets when they are heated? Check This Out Nothing They stop being magnetic They explode

Magnetic Field Lines

Electricity vs. Magnetism To each statement about electric charges, write a corresponding statement about magnets. There are positive and negative electric charges. Electric charge is due to the excess or deficit of electrons. Electrically charged objects can attract or repel other charged objects and neutral objects. Electric charges don’t require contact in order to exert a force.

Homework! Pg. 552 #5ab, 6abd Read and take notes on “Magnetic Fields at Work” Pg. 550-551