Magnets

Noah and Priya are building an electromagnet for their science project. Choose the 3 ways they can make a more powerful electromagnet.

• Use more iron.

• Use fewer coils.

• Use more coils of wire.

• Use more batteries.

• Use a plastic core.

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A student did an experiment with magnets to see which poles repel each other. Look at the results and choose the images that show the magnets with repelling poles.

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Emma is working on a science project where she needs to convert mechanical energy into electrical energy. What device should she use?

• Electric generator

• Electric current

• Electric motor

• Electromagnet

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Electromagnetic lifting cranes use electromagnetism to magnetize the coil for lifting and demagnetize the coil for dropping materials in the correct place. This technology is possible because of a phenomenon that

• The coil in the electromagnet is a good insulator

• Magnetic fields and electricity are not related

• Electricity can be used to create a magnetic force

• A balance of charge creates static electricity

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Abigail makes four models to test how the strength of an electromagnet can be increased, as shown in the image. Which variable is being changed in the given model?

• Thickness of the iron nail

• Voltage of the battery

• Number of coils of wire on the nail

• Length of the connecting wire

Answer explanation

The variable being changed in the model is the number of coils of wire on the nail. Increasing the coils enhances the electromagnet's strength, making it the key factor in this experiment.

Ava and Liam are experimenting with a coil and a magnet. They notice that moving the magnet through the coil produces an electrical current. This phenomenon is called _______.

• electromagnetic circuit

• electromagnetic induction

• electromagnetic convection

• electromagnetic conduction

Answer explanation

The process of changing a magnetic field to generate an electrical current in conductors is known as electromagnetic induction. This phenomenon is fundamental in the operation of generators and transformers.

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Nora is working on a science project and needs to choose between using an electromagnet and a permanent magnet. What is an advantage of electromagnets over permanent magnets?

• Electromagnets can be turned on and off.

• Electromagnets do not have poles.

• Permanent magnets last longer.

• Electromagnets are smaller.

Answer explanation

An advantage of electromagnets is that they can be turned on and off, allowing for greater control in applications. In contrast, permanent magnets always maintain their magnetic field.

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Rohan is using a kitchen mixer to bake a cake. The motor in the kitchen mixer converts:

• electrical energy (electricity) into mechanical energy (moving position)

• chemical energy into mechanical energy (moving position)

• electrical energy (electricity) into chemical energy

• mechanical energy (moving position) into electrical energy (electricity)

Answer explanation

The motor in a kitchen mixer takes electrical energy (electricity) and converts it into mechanical energy (moving position) to mix ingredients, making the first option the correct choice.

Emma and Isla are playing with magnets. What is true about the properties of the magnets they are using?

• • - Can be permanent or temporary.

  • - Have North, South East and West Poles.

  • - Opposite poles attract.

  • - Have a magnetic field.

• • - Can be permanent or temporary.

  • - Have North and South poles.

  • - Opposite poles attract.

  • - Have a magnetic field.

• - Can be permanent or temporary.

  - Have North and South Poles.

  • - Opposite poles attract.

  • - Do not have a magnetic field.

• - Can be permanent or temporary.

  - Have North and South poles.

  • - Like poles attract.

  • - Have a magnetic field.

Answer explanation

Magnets can be permanent or temporary, have North and South poles, opposite poles attract, and possess a magnetic field. The correct properties are all included in the correct answer choice.

Maya was learning about how Earth acts like a magnet because of the metals in the core of the planet. She discovered that the magnetic field around the Earth is strongest at the poles. The Earth's magnetic field is similar to a bar magnet. The Earth's magnetic field interacts with the magnetic needle of a compass and allows people to determine direction. The magnetic needle turns and aligns to the Earth's magnetic north and south poles.

The Earth's magnetic field also shields the Earth's surface from harmful solar radiation. Electric particles from the sun travel through space and instead of hitting the Earth's surface, they follow the Earth's magnetic field lines toward the poles and then back into space. Auroras are found around the Earth's poles when some of the electric sun particles energize gas atoms in the atmosphere.

After reading, choose the 3 correct statements.

• A compass needle turns toward the Earth's north and south poles.

• The Earth magnetic field protect us from solar radiation

• Auroras are found in the atmosphere.

• The Earth magnetic field is weakest at the poles.

Answer explanation

A compass needle aligns with the Earth's magnetic field, pointing to the north and south poles. The magnetic field also protects us from solar radiation, and auroras occur when solar particles interact with atmospheric gases.