Unit 6: Magnetism Chapter 16: Electromagnets and Induction 16.1 Electric Current and Magnetism 16.2 Electric Motors 16.3 Electric Generators and Transformers 10 minutes

SWBAT explain how motion due to magnets is important to motors. Objective Date: 3/23 SWBAT explain how motion due to magnets is important to motors.

Electric Current and Magnetism In 1819, Hans Christian Oersted, a Danish physicist and chemist, and a professor, placed a compass needle near a wire through which he could make electric current flow. When the switch was closed, the compass needle moved just as if the wire were a magnet.

Electric current and magnetism Electric current is made of moving charges (electrons), which creates the magnetic field around a current-carrying wire. This creates the magnetism.

The magnetic fields of straight wire The magnetic field lines are circles with the wire at the center of the circles. The direction of the field depends on the direction of the current in the wire.

The magnetic fields of straight wire The strength of the magnetic field near the wire depends on two factors: The strength is directly proportional to the current, so doubling the current doubles the strength of the field. The field strength is indirectly proportional to the distance from the wire. (Decreasing the distance to the wire by half doubles the strength of the field.)

The magnetic fields of straight wire _____________Strength ____________Current ______________Distance

The magnetic fields of loops and coils The most common form of electromagnetic device is a coil with many turns called a solenoid. A coil takes advantage of these two techniques (bundling wires and making bundled wires into coils) for increasing field strength. 8

Magnetic forces and electric currents Two wires carrying electric current exert force on each other, just like two magnets. The forces can be attractive or repulsive depending on the direction of current in both wires.

16.1 Investigation: Electromagnetic Forces Key Question: How does an electric motor work? Objectives: Build a simple electric motor. Describe the components required for an electric motor to work. Test the effects of changing different variables on the function of an electric motor.