# Magnetic Forces All magnets have two magnetic poles, regions where the magnet’s force is strongest. One end of a magnet is its north pole. The other end.

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Magnetic Forces All magnets have two magnetic poles, regions where the magnet’s force is strongest. One end of a magnet is its north pole. The other end is its south pole. The direction of the magnetic force between two magnets depends on how the poles face.

Magnetic Fields A magnetic field surrounds every magnet. Iron filings reveal the field lines, which start near the north pole and extend toward the south pole. Where lines are close together, the field is strong. Where lines are more spread out, the field is weak.

Magnetic Fields When like poles of two magnets come together, the magnets repel each other. When opposite poles of magnets come together, the magnets attract each other.

Magnetic Materials If you cut a magnet in half, each half will have its own north pole and south pole because the domains will still be aligned. A magnet can never have just a north pole or just a south pole.

Magnetic Materials A magnetic field can magnetize ferromagnetic materials. Before magnetization, domains are random. Domains aligned with the field grow during magnetization. Unaligned domains can shrink.

Electricity and Magnetism
Electricity and magnetism are different aspects of a single force known as the electromagnetic force. The electric force results from charged particles. The magnetic force usually results from the movement of electrons in an atom.

Electricity and Magnetism
Magnetic Fields Around Moving Charges Moving charges create a magnetic field. Moving charges may be the vibrating charges that produce an electromagnetic wave or the moving charges in a wire. Magnetic field lines form circles around a straight wire carrying a current.

Electricity and Magnetism
If you point the thumb of your right hand in the direction of the current, your fingers curve in the direction of the magnetic field. Direction of current Current-carrying wire Direction of electron flow Direction of magnetic field

Solenoids and Electromagnets
A coil of current-carrying wire that produces a magnetic field is called a solenoid. The magnetic field lines around a solenoid are like those of a bar magnet.

Solenoids and Electromagnets
he strength of an electromagnet can be increased using the following methods. Increase the current flowing through the solenoid. Increase the number of turns. Adding a metal core.

Electromagnetic Devices
Electric Motors An electric motor is a device that uses an electromagnet to turn an axle.

Assessment Questions Where does the magnetic field of a magnet have the strongest effect on another magnet? the north pole the south pole both poles equally midway between the two poles

Assessment Questions Where does the magnetic field of a magnet have the strongest effect on another magnet? the north pole the south pole both poles equally midway between the two poles ANS: C

Assessment Questions 2. What happens to a permanent magnet if its magnetic domains lose their alignment? The magnetic field reverses direction. It loses its magnetic field. It has several north poles and several south poles. It is no longer a ferromagnetic material.

Assessment Questions 2. What happens to a permanent magnet if its magnetic domains lose their alignment? The magnetic field reverses direction. It loses its magnetic field. It has several north poles and several south poles. It is no longer a ferromagnetic material. ANS: B

Assessment Questions 3. Which change will increase the strength of an electromagnet made by wrapping a conductive wire around an iron nail? reversing the direction of current flow replacing the nail with a wooden dowel increasing the number of coils of wire around the nail using a longer nail

Assessment Questions 3.Which change will increase the strength of an electromagnet made by wrapping a conductive wire around an iron nail? reversing the direction of current flow replacing the nail with a wooden dowel increasing the number of coils of wire around the nail using a longer nail ANS: C

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