Electricity and Magnetism

Electricity and Magnetism

Middle School

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Learning Objectives

• Define electric charge and describe the forces between protons and electrons.

• Explain the differences between conductors, insulators, and semiconductors.

• Explain the difference between Direct Current (DC) and Alternating Current (AC).

• Describe how an electric current can produce a magnetic field.

• Explain the basic principles of devices like motors, generators, and transformers.

Key Vocabulary

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Electric Charge

A property of matter that causes a force when it is near other electrically charged matter.

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Conductor

A material, like copper, that allows electrons to move freely from one atom to another.

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Insulator

A material, such as rubber, that does not permit electrons to move freely among atoms.

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Electric Current

The movement or flow of charged particles, which are typically electrons in a specific direction.

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Direct Current (DC)

An electric current that consistently flows in only one direction, commonly used in battery-powered devices.

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Alternating Current (AC)

An electric current that rapidly flows back and forth, which is used in household wiring.

Key Vocabulary

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Electromagnet

A magnet created when charged particles move through a wire coil connected to a power source.

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Transformer

A device that changes an electric current's voltage using fluctuating magnetic fields and coiled wires.

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Electric Charges and Fields

• At the atomic level, electrons have a negative charge and protons are positive.

• Particles with like charges will repel, or push away from, each other.

• Particles with unlike charges attract, which can create static electricity.

• All charges produce an electric field, showing the direction of the force.

Multiple Choice

What is the fundamental principle that describes how particles with opposite electric charges, like a proton and an electron, interact?

• They attract, or pull toward, each other.

• They have no effect on one another.

• They cancel each other's mass out.

• They repel, or push away from, each other.

Multiple Choice

Based on their charges, what would happen if two protons were brought close to each other?

• Nothing would happen because protons do not have a charge.

• They would repel each other because they have like charges.

• They would attract each other because they are both part of an atom.

• They would create static electricity because they have unlike charges.

Multiple Choice

What does an electric field produced by a charge show?

• The number of electrons in the charge

• The path a charged particle must follow

• The direction of the force that another charge would experience

• The speed of moving charges

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Types of Electric Current

Direct Current (DC)

• An electric current is the movement of charged particles, which are usually electrons.

• Direct current is a type of current that flows in only one direction.

• This is the type of current supplied by batteries for devices like flashlights.

Alternating Current (AC)

• Alternating current is a type of current that rapidly flows back and forth.

• This is the standard type of electricity used for household wiring.

• It is used to power home appliances such as toasters and washing machines.

Multiple Choice

What is an electric current?

• The power used by household appliances.

• The flow of electricity in two directions.

• The energy stored inside a battery.

• The movement of charged particles, like electrons.

Multiple Choice

What is the primary difference between direct current (DC) and alternating current (AC)?

• DC is made of protons, while AC is made of electrons.

• DC flows in one direction, while AC flows back and forth.

• DC is used for appliances, while AC is used for flashlights.

• DC is a much stronger type of current than AC.

Multiple Choice

A person needs to power a portable camping lantern that uses batteries. Which type of current does the lantern use and why?

• Alternating current (AC), because it is used in most appliances.

• Alternating current (AC), because it flows back and forth rapidly.

• Direct current (DC), because it is used in household wiring.

• Direct current (DC), because it is supplied by batteries.

Conductors, Insulators, and Semiconductors

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Conductors

• ​Materials that allow electrons to move freely from atom to atom.

• ​​They permit the flow of electric charge and are used for wiring.

• ​Aluminum and copper are two common examples of good conductors.

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Insulators

• ​Materials that do not allow electrons to move freely through them.

• ​​Because they block electric charge, they are used for safety.

• ​Rubber and plastic are very common examples of good insulators.

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Semiconductors

• ​Materials with properties between conductors and insulators.

• ​​They are not as conductive as copper but not as insulating.

• ​Silicon is a well-known example used in many electronic devices.

Multiple Choice

What characteristic determines if a material is a conductor?

• It has properties between a conductor and an insulator.

• It does not allow electrons to move through it.

• It allows electrons to move freely between atoms.

• It is primarily used for safety to block electric charge.

Multiple Choice

Why are materials like rubber and plastic often used for electrical safety?

• Because they are semiconductors used in electronic devices.

• Because they are common materials like aluminum and copper.

• Because they are insulators that block the flow of electric charge.

• Because they are conductors that allow electricity to flow easily.

Multiple Choice

An engineer needs a material for a new electronic device that can carefully control the amount of electric charge flowing through it. Which material would be the best choice for this specific task?

• Rubber, because it is a good insulator and prevents all charge flow.

• Copper, because it is a good conductor and allows maximum charge flow.

• Silicon, because it is a semiconductor with properties between a conductor and an insulator.

• Aluminum, because it is a common and inexpensive wiring material.

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Magnetism and Magnetic Fields

• An electric current creates a magnetic field, which is used in electromagnets.

• In permanent magnets, the magnetic field is generated by the spinning of electrons.

• Every magnet has two ends, called the north pole and the south pole.

• Opposite poles attract each other, but like poles will push each other away.

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Multiple Choice

What are the two sources described as creating magnetic fields?

• Attraction and repulsion forces

• An electric current and the spinning of electrons

• The north pole and the south pole

• Electromagnets and permanent magnets

Multiple Choice

Which statement best explains the relationship between a magnet's poles?

• Both north and south poles will attract any other pole.

• Like poles will push each other away, while opposite poles will pull together.

• Like poles will attract each other, and opposite poles will repel.

• A magnet's poles do not interact with the poles of other magnets.

Multiple Choice

If you bring the north pole of one magnet close to the north pole of a second magnet, what outcome can you predict?

• The two magnets will pull toward each other.

• The magnets will both lose their magnetic field.

• The two magnets will push away from each other.

• One magnet will flip its pole from north to south.

Applications of Electromagnetism

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Electric Motor

• An electric current creates a magnetic field that causes rotation.

• The magnetic fields push against one another, causing movement.

• This spinning motion is what powers the device.

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Generator

• A moving magnetic field is used to create an electric current.

• This process is the opposite of how an electric motor works.

• Power plants use generators to produce electricity for our homes.

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Transformer

• A current in one coil creates a changing magnetic field.

• The field induces a new current in a second wire coil.

• Different coil sizes allow it to change the electricity’s voltage.

Multiple Choice

Which statement describes the fundamental principle that allows devices like electric motors and generators to function?

• Friction between two objects can be used to create heat.

• Electricity can create a magnetic field, and a moving magnetic field can create electricity.

• Static electricity builds up when certain materials are rubbed together.

• Energy can be created or destroyed in a closed system.

Multiple Choice

What is the main difference in the function of an electric motor compared to a generator?

• A motor changes voltage using two coils, while a generator creates rotation.

• A motor uses a current to create motion, while a generator uses motion to create a current.

• A motor uses motion to create a current, while a generator uses a current to create motion.

• A motor creates a static magnetic field, while a generator creates a changing electric field.

Multiple Choice

How does an electric transformer work?

• It stores electrical energy in one coil without transferring it to another coil.

• A changing current in one coil creates a magnetic field, which induces a current in a second coil; different coil sizes change the voltage.

• It converts a direct current into alternating current without using coils.

• It generates a magnetic field that permanently magnetizes nearby metal objects.

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Common Misconceptions

Misconception	Correction
Magnets only attract things.	Magnets can also repel other magnets when like poles face each other.
All metals are magnetic.	Not all metals are magnetic. Iron is magnetic, but aluminum is not.
Static electricity is different from current electricity.	Both are related to electric charges, but one is stationary while one flows.

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Summary

• Electric charge causes attraction and repulsion; its flow is called electric current.

• Currents, either DC or AC, flow through conductors but are blocked by insulators.

• Electric currents create magnetic fields, while electron spin creates permanent magnetism.

• This relationship powers devices like motors, generators, and transformers.

Poll

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

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