Magnetic and Electromagnetic Forces

The attractive force between two magnets increases. Which statement explains why this would happen?

• The like poles of the magnets are pointed at each other and move farther apart.

• The like poles of the magnets are pointed at each other and move closer together.

• The unlike poles of the magnets are pointed at each other and move farther apart.

• The unlike poles of the magnets are pointed at each other and move closer together.

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Which of these determines whether or not a material is magnetic?

• the density of the material

• the weight of the material on Earth

• the alignment of atoms in the material

• the number of elements that make up the material

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Christopher claims that all magnets have two magnetic poles. Which of these observations would best support this claim?

• Iron is attracted to a magnet but not to other pieces of iron.

• When a bar magnet is cut in half, each half has a north pole and a south pole.

• The north pole of a compass needle is attracted to the south pole of a bar magnet.

• The strength of the magnetic force from a bar magnet decreases as the magnet is pulled away from another object.

Which of these is the best definition of electromagnetism?

• the use of electrical energy to produce magnets

• the use of magnets to generate electric current

• the interaction of electricity and magnetism

• the appearance in nature of objects that have both electric and magnetic fields

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An electromagnet is made by wrapping many turns of wire around an iron bar and causing a current to flow through the wire. How would increasing the electrical current affect the electromagnet?

• It would make the magnetic field of the magnet weaker.

• It would make the magnetic field of the magnet stronger.

• It would decrease the flow of electricity in the iron bar.

• It would increase the flow of electricity in the iron bar.

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NGSS.MS-PS2-3

Which statement describes how electromagnetism is used in an electric generator?

• Moving a magnet in a coil of wire produces visible light.

• Magnets convert electric energy into mechanical energy.

• Magnets detect the presence of electric currents in nature.

• Moving a magnet in a coil of wire generates an electric current.

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NGSS.MS-PS2-3

Olga wants to test if the battery shown in the diagram still produces an electric current. She wraps a wire around a compass and connects each end to the battery as shown in the diagram.

She claims that this device has properties similar to an electromagnet. Which of these statements about what happens when electric charges flow through the wire best defends this claim?

• The voltage of the battery increases.

• The compass becomes demagnetized.

• The compass becomes electrically charged.

• A magnetic field is concentrated inside the coil of wire.

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