First Five Silently enter the room and sit down in your assigned seat. Begin working on your Activator. When you’ve completed your Activator, read your DEAR book.

Today’s Objectives SWBAT explain identify ways to increase the strength of an electromagnet in order to describe the structure and function of an electromagnet.

When electric current (moving electrons) is passed through wire, a magnetic field is formed around the wire The production of a magnetic field by electric current is called electromagnetism.

Right Hand Grip Rule Thumb – direction of current Fingers – direction of magnetic field produced

This is how some researchers expected the magnetic field to look like around a current carrying wire.

Note that the magnetic field does not start or stop on any poles Note that the magnetic field does not start or stop on any poles. The greater the current the stronger the field. If the current were reversed in the wire the field would circle the wire in the other direction (here the current is defined to be the flow of positive charge. Right!

A solenoid is a coil of wire that produces a magnetic field when carrying an electric current. The electricity is what produces the magnetic field

An electromagnet uses the combined magnetic fields of many loops of current carrying wire to magnetize a core of iron, thereby intensifying the net magnetic field. The more loops and the greater the current, the stronger the magnetic field.

A magnet that is made by passing an electric current through a wire (in the form of a solenoid) wrapped around an iron core is called an electromagnet.

While current flows, the core behaves like a magnet But, as soon as the current stops, the magnetic properties are lost.

The Magnetic Field of an Electromagnet The magnetic field produced around the wire is similar to that surrounding a bar magnet. The magnetic south pole is where the current (abbreviated by I) goes in and the magnetic north pole is where it exits in the wire coil Just like in all magnets, the direction of the field still moves from north to south

Ways to Increase the Strength of an Electromagnet Increasing the current running through the solenoid (which can be done by increasing the voltage of the electrical source or by) One way to increase the voltage is to add another battery Placing an iron core at the center of the coil Increasing the number of coils of the wire or solenoid Increasing the thickness of the wire coil

Advantages of electromagnets Turning Electromagnets On and Off Electromagnets are very useful because they can be turned on and off as needed. The solenoid has a field only when there is electric current in it. Changing Polarity Electromagnets are also very useful to change polarity (north pole becomes south pole)

Electromagnetism Anything that uses electricity or a motor most likely uses electromagnetism.

Everybody Writes A magnet can be made by wrapping a _______into a coil and attaching the ends of the wire to the terminals of a battery cell. This magnet is called a(n)______________________. The strength of an electromagnet is affected by the number of ______ in the wire. The strength of an electromagnet is affected by the amount of electrical ___________ in the wire. The strength of an electromagnet is affected by the material (core) the wire is wrapped around. This core is most likely made of _________.