Electric and magnetic forces

Which of the two below result in an attractive force?

• A positive charge and a negative charge

• Two negative charges

• Two south poles

• A north pole and a south pole

• Two postive charges

Answer explanation

An attractive force is generated between a positive charge and a negative charge, as well as between a north pole and a south pole.

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Static electricity is the buildup of charges between two objects. What best explains why a balloon is attracted to hair when the two have been rubbed together?

• The balloon and hair both have positive charges

• The balloon and the hair both have negative charges

• The balloon and the hair both have neutral charges

• The balloon and the hair both have opposite charges

Answer explanation

The balloon and the hair both have opposite charges, leading to attraction due to static electricity.

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Which of the following most closely resembles an electromagnetic?

• 
• 
• 
• 

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Two bar magnets are held close together. They are released and allowed to move freely. The bar magnets quickly come together. Which best explains why this happens?

• The poles facing one another are both south poles

• The poles facing one another are both north poles

• The poles facing one another are opposite poles

• One magnet was bigger than the other

Answer explanation

The poles facing one another are opposite poles, which causes the bar magnets to quickly come together due to the attraction between opposite poles.

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Frederick sets paper clips out on a table. He then takes a magnet, places it directly beneath the paper clips under the table, and moves the magnet. He finds that the paper clips move with the magnet. Why does this happen?

• Magnetic force is a repellant force

• Magnetic forces act on wood, like in the table

• The paper clips are feeling the gravitational force of the magnet

• Magnetic forces act at a distance, even between objects

Answer explanation

Magnetic forces act at a distance, even between objects

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Surrounding each magnetic is an invisible force field called

• Gravity

• A magnetic field

• An electric field

• The Force

Answer explanation

The correct answer is 'A magnetic field' because the invisible force field surrounding each magnet is called a magnetic field.

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In an electromagnet, coils of wire are wrapped around a magnetic object to generate a magnetic field. What the is relationship between number of coils and the strength of the magnetic field?

• The more coils an electromagnetic has, the stronger the magnetic field

• The more coils an electromagntic has, the weaker the magnetic field

• The larger the metal object, the stronger the magnetic field is

• There is no relationship between number of coils and the strength of a magnetic field

Answer explanation

The more coils an electromagnetic has, the stronger the magnetic field

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To decrease the strength of a magnetic field around an electromagnet, we must

• increase the number of coils

• increase the size of the iron core

• decrease the size of the iron core

• decrease the number of coils

Answer explanation

To decrease the strength of a magnetic field around an electromagnet, we must decrease the number of coils.

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What is the cause of electricity?

• Magnetism

• Gravity

• Moving electrons

• Lightning

Answer explanation

Electricity is caused by the movement of electrons, which creates an electric current that can be harnessed for various purposes.

When electrons in magnetic domains all spin in the same direction, they create an invisible force known as_______

• Electricity

• Magnetism

• Static Electricity

• Electromagnet

Answer explanation

When electrons in magnetic domains all spin in the same direction, they create an invisible force known as Magnetism.

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