What Is Electromagnetism? CHAPTER 3 SECTION 1

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OBJECTIVES N Explain how electric current is related to magnetic fields. N Identify some characteristics of a magnetic field produced by an electric current. N Describe the characteristics of an electromagnet.

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ELECTRIC CURRENT AND MAGNETISM An electric current produces a magnetic field. Objective N Whenever electricity flows through a wire, the moving electrons (electric charges) produce a magnetic field around the wire.

SOLENOIDS The magnetic field produced by an electric current has three distinctive features: Objective N ) It can be turned on and off. 2) Its direction can be reversed. 3) Its strength can be adjusted.

A coil of wire with a current in it is called a solenoid and the ends of the solenoid act like poles in a bar magnet. The magnetic field around a solenoid is the same as a magnetic field around a bar magnet with the two poles: North Pole South Pole SOLENOIDS

SolenoidBar Magnet

When you put a ferromagnetic material inside a solenoid and pass electric current through the wire, you make an electromagnet. What is the biggest advantage to an electromagnet vs. a regular one? They can be turned on and off. Objective N ELECTROMAGNETS

Electromagnets are often used in junkyards to separate iron from other materials. ELECTROMAGNETS

Can anyone think of how they might be used in the food industry? They are often used to remove metals from the food stream or to check foods for metals to protect your health. ELECTROMAGNETS

ASSESSMENT

1a. Who discovered that electricity and magnetism are related? Hans Christian Oersted 1b. What is the relationship between electric current and magnetism? An electric current in a wire creates a magnetic field around it. 1c. How can a magnetic field be produced around a wire? By putting current through the wire.

ASSESSMENT 2a. What is a solenoid? A solenoid is a coil of wire that mimics a bar magnet when a current is passed through it. 2b. What are three characteristics of a magnetic field produced by a current? They can be turned on and off. The magnetic field can be reversed. The strength of the magnet can be adjusted.

ASSESSMENT 2c. How could you increase the strength of a solenoid? Add more turns of wire. Add an iron core to it. Increase the current in the wire. 3a. What makes an electromagnet stronger than a solenoid? An electromagnet has an iron core inside the solenoid.

ASSESSMENT 3b. What are the four ways to make an electromagnet stronger? Increase the current in the coil. Add more turns of wire to the solenoid. Make the loops in the solenoid smaller or tighter. Add a stronger ferromagnetic material to the core.

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