Electromagnetism

Electromagnetism

Middle School

​

Learning Objectives

• Define open and closed circuits and identify their essential components.

• Explain how electric and magnetic fields create forces that act at a distance.

• Describe factors affecting the strength of electric and magnetic forces.

• Identify applications of electromagnetism, such as in motors and generators.

Key Vocabulary

​

Circuit

A complete and closed path through which electrical current can flow from a source.

​

Electromagnet

A type of magnet where the magnetic field is produced by an electric current.

​

Electric Field

A region around a charged particle where a force is exerted on other charged particles.

​

Magnetic Field

A region around a magnetic material or a moving charge where a magnetic force is exerted.

​

Potential Energy

Energy held by an object because of its position relative to other objects in a system.

​

​

What is an Electric Circuit?

Closed Circuit

• A simple circuit requires an energy source like a battery, a path such as wires, and a device.

• For electricity to flow, the circuit must form a complete and unbroken path from the source and back.

• Wires need exposed metal at contact points to conduct electricity, lighting up a bulb in a closed circuit.

Open Circuit

• An open circuit is an electrical path that has a break or gap, making it incomplete.

• This break in the path completely stops the flow of electricity, acting like an off switch.

• Because electricity cannot flow, it cannot power any connected devices, so the bulb remains unlit.

Multiple Choice

What is the main requirement for an electric current to flow through a circuit?

• A complete and unbroken path

• A path made of a flexible material

• At least two lightbulbs

• A single point of contact

​

​

What Is Electromagnetism?

• An electric current flowing through a wire creates a magnetic field around it.

• This fundamental relationship was discovered by scientist Hans Christian Ørsted.

• Wrapping a wire coil around an iron core creates a powerful electromagnet.

• This magnet can be controlled by turning the electric current on or off.

​

Multiple Choice

Based on Hans Christian Ørsted's discovery, how can the magnetic field created by an electric current be made stronger?

• By coiling the wire carrying the current

• By using a much shorter wire

• By removing the iron core from the coil

• By decreasing the electric current

​

​

Electric and Magnetic Fields

Electric Fields

• An electric field is an invisible area of force that surrounds an electric charge.

• This field can attract or repel other charged objects that enter the area.

• The force works at a distance, meaning the objects do not have to touch.

Magnetic Fields

• A magnetic field is an invisible area of force around a magnet or electric current.

• It exerts a force on magnetic materials, such as iron, and other magnets.

• Like an electric field, this magnetic force can act on objects from a distance.

Multiple Choice

What is the key difference in how electric and magnetic fields exert a force?

• An electric field acts on charged objects, while a magnetic field acts on magnetic materials.

• An electric field is invisible, while a magnetic field can be seen.

• An electric field is created by a current, while a magnetic field is created by a stationary charge.

• An electric field is mapped with a compass, while a magnetic field is mapped with a test charge.

​

​

Potential Energy in Fields

• Potential energy is stored energy based on an object's position or arrangement.

• ​This stored energy is not in motion, but it can cause motion.

• Pulling apart two attracting magnets increases the system’s potential energy.

• Pushing two repelling magnets together also increases their potential energy.

​

Multiple Choice

What is potential energy?

• Energy stored in a system of objects based on their position

• Energy that an object has because of its motion

• Energy that is created when magnets get hot

• Energy that is lost when objects move

​

​

Applications and Force Factors

• Electromagnets are used in devices like speakers, headphones, and even telegraphs.

• In a speaker, an electromagnet vibrates a cone to create sound waves.

• The force is stronger with more wire coils or more electric current.

• The magnetic force gets stronger as an object gets closer to it.

​

Multiple Choice

What determines the strength of an electromagnet's force?

• By increasing the number of wire coils or the electric current.

• By decreasing the distance between the magnet and an object.

• By using it in applications like speakers and telegraphs.

• By changing the orientation of the magnet from attractive to repulsive.

​

​

What Are Superconducting Magnets?

• Superconducting magnets are electromagnets with wires that are cooled to low temperatures.

• When cooled, the wires have zero electrical resistance, becoming '''superconducting.'''

• This lets current flow without losing any energy as heat.

• This allows them to create powerful and stable magnetic fields.

​

Multiple Choice

What is a defining characteristic of a superconducting magnet?

• They are cooled to extremely low temperatures to function.

• They generate weak, temporary magnetic fields.

• They operate best at very high temperatures.

• They are a type of permanent magnet found in nature.

​

Common Misconceptions

Misconception	Correction
All magnets are permanent and found in nature.	Electromagnets are temporary and need an electric current to be magnetic.
An open circuit can still power a device weakly.	An open circuit stops the flow of electricity completely.
Electric and magnetic fields are the same thing.	Electric fields act on charges; magnetic fields on moving charges and magnets.

Multiple Choice

A string of holiday lights is designed so that if one bulb burns out, the entire string goes dark. Based on the principles of electricity, what is the best explanation for this?

• The burned-out bulb creates a break in the circuit, stopping the flow of current.

• The flow of electricity reverses direction and returns to the source.

• The burned-out bulb uses up all the electricity from the outlet.

• The other bulbs are drained of their static electricity.

Multiple Choice

An engineer is building a telegraph to send messages over a very long distance, but the signal is too weak. What should the engineer do to increase the force of the electromagnet and make the signal stronger?

• Increase the number of wire coils and the electric current.

• Use the electromagnet in a headphone instead of a telegraph.

• Change the orientation of the magnet to make it repulsive.

• Move the interacting objects farther apart.

Multiple Choice

If you detect an invisible force in an area, what is the best method to determine if it is an electric or a magnetic field?

• Use a compass to see if it moves, and then use a charged object to see if it is affected.

• Assume it is an electric field, as they are created by charged objects.

• Measure the size of the field, as electric fields are always larger than magnetic fields.

• Place a small light bulb in the area to see if it lights up.

Multiple Choice

If the cooling system of a maglev train's superconducting magnet were to fail, what would be the most likely outcome?

• The magnet's powerful magnetic field would collapse.

• The magnet would become a permanent magnet.

• The magnet would generate even more energy.

• The maglev train or MRI machine would speed up.

​

Summary

• A complete, closed circuit is required for electricity to flow and power devices.

• Electromagnetism is the relationship between electricity and magnetism.

• An electromagnet’s strength depends on the current, number of coils, and distance.

• Electromagnets are essential in modern technologies like speakers and superconducting magnets.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4