# Electrical Currents and Circuits

In this unit, students continue to explore forces and energy, focusing on the science phenomenon of how electrical energy can be transferred from one place to another to do work. In this lesson, students build series and parallel circuits, measuring the amount of current that moves through each circuit with one and two light bulbs. This page highlights some components of that lesson.

## Science Background for Teachers:

Science background gives teachers more in-depth information about the phenomena students explore in this unit on matter and electricity. Here is an excerpt of the science background information for this lesson.

Understanding the phenomena of electricity begins with the basic particles of matter: atoms. Remember that all matter is made of atoms, which are the smallest pieces of matter that have the properties of an element. Atoms are so tiny that we cannot see them.

Atoms themselves are made up of smaller particles, called protons, neutrons, and electrons. Electrons have a negative charge (-) and are attracted to positively charged protons (+).

The force that holds protons and electrons together in an atom is called electromagnetic force. It occurs whenever particles are charged, causing them to either attract or repel one another. Particles with an opposite charge attract one another, while particles with the same charge repel one another. Electrons are kept in orbit in their shells because the positive charge of the protons in the nucleus attracts the negatively charged electrons.

Protons repel each other in the nucleus because they all have a positive charge, but they stay together because of another force, called the strong force. The strong force counters electromagnetic force because it is the strongest attractive force, 137 times more powerful than electromagnetic force. However, it only exerts a force over very short distances, and so it does not exert a force over electrons.

Electrons that are in shells closest to the nucleus are tightly bound to the positive protons because of electromagnetic force. Just like the strong force, electromagnetic force weakens with distance, so electrons in the outermost shell are much more loosely bound. When a force is applied to certain kinds of matter, those farther electrons can be pushed from one atom to another.

Electrons can move more easily through some kinds of materials than others. Materials that allow electrons to pass through are called electrical conductors. Metals are common conductors. Silver, copper, bronze, and aluminum are all metals and good conductors.

Some materials don’t allow electrons to pass through as easily. These materials are called electrical insulators. Glass, rubber, plastic, and ceramic are all good insulators.

When electrons move through a conductor, it produces electricity. There are two kinds of electricity: static and current. Static electricity is a type of electricity that results from the buildup of electric charge on the surface of an object.

Current electricity is a type of electricity in which electrons move through a circuit. A circuit is the circular path electrons travel from a negative charge to a positive charge. Electronic devices use electric current by directing it through the wires of a circuit. The electrons are first pushed through a wire by a power source, such as a battery or electrical generator. From there, the electric current travels through the wire until it reaches an object that can do work.

For example, a passing electric current can light a light bulb, warm a toaster, or turn on a computer. This is because moving electrons carry with them electrical energy that is converted to another form of energy, such as light energy or heat. Energy is conserved, which means the same amount of energy that is carried by the electrons is converted to do work. The electrical current then travels down a second wire back to the power source. The entire circuit forms a circular loop.

A circuit must be complete and unbroken to function properly. If the wire is broken, the circuit is open and the electricity stops moving. The air between the broken wires will not conduct or transport the electrons. The wire must be repaired to close the circuit and restart the electron flow. There are four main parts of a circuit.

• All circuits have an energy source. Many circuits use a battery, which has stored chemical energy that converts to electrical energy. This energy provides the push that makes the electrons in the conductive material move through the circuit from the negative end of the battery through the circuit to the positive end. They move because the negatively charged electrons are attracted to the positive side of the battery.
• Wires create a path of conducting material for electrons to travel. As the electrons move, energy is carried from the battery through the conductors inside the wires.
• The wires in a circuit are attached to an object that can convert electrical energy to do work (any change in position, speed, or state of matter due to force). For example, a light bulb is an object that does work. When electrons reach the light bulb in a circuit, electrical energy is changed into light energy. The electrons then continue on their path, returning to the opposite side of the battery. All circuits must include something that can do work. Without this part, the electricity will cause danger by overheating the circuit. This is called a “short circuit.
• The switch opens and closes the circuit. Electrons flow when a circuit is closed. This is “on.” A closed circuit can be used to charge a cell phone or turn on a light. Electrons cannot flow when a circuit is open. This is “off.” No work can be done in an open circuit.

## Science Lesson: Discovering Electrical Currents and Circuits

In this lesson, students explore how energy can be transferred from one place to another in a circuit. Students investigate one property of matter—electric conductivity—to test their circuits, observing whether the material allows electricity to flow through it.

## Science Big Ideas

• Electricity is the flow of electrons through a conductor.
• Moving electrons transfer electrical energy through a circuit.
• Circuits are the circular paths that electrons travel in a negative to positive direction. Circuits are used to transfer electrical energy from one place to another.
• Materials that allow electrons to pass through are called electrical conductors. Materials that don’t allow electrons to pass through easily are called electrical insulators.
• There are different ways that a circuit can be designed, and the design will affect the amount of current that can be used to do work.

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## Science Essential Questions

• Why is electricity important for people?
• Why are some materials called electrical conductors and other materials called electrical insulators?
• Why are light cords made up of both conductors and insulators?
• Why do many circuits have a battery?
• Why do batteries have a positive and a negative end?
• Why do circuits need some object that can do work? What would happen to a circuit if it didn’t have any object that could do work?
• Where does the energy in a circuit originate from?
• How does the amount of energy change as it moves through the circuit?
• What makes a light bulb shine more brightly?
• How is the simple circuit different from either the parallel circuit or the series circuit?

## Common Science Misconceptions

Misconception: Batteries create electricity.
Fact: Batteries provide the force that pushes electrons through a conductor. When electrons move through a conductor, it produces direct current (DC) electricity.
Misconception: Conductive wires are hollow so that electricity can flow through them.
Fact: Like all matter, conductive wires are made up of atoms that have electrons. These electrons just need a force applied, such as a push from a battery, to begin to move from one atom to another.

## Science Vocabulary

Circuit : the circular path electrons travel in a negative to positive direction

Current :  a measure of the rate that electric charge passes through a point in an electric circuit over time; measured in amps

Electricity :  the flow of electrons through a conductor 4. electric conductor – a material that electrons can easily pass through

Electric Insulator :  a material that electrons cannot pass through easily

Electromagnet :  a tightly wound coil of wire that produces a magnetic field when electricity passes through the wire

Motor :  a machine that converts an input of energy into an output of kinetic energy

Permanent Magnet :  an object that stays magnetized without electricity

## Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

Holiday Lights

Adam Atkinson has a bright hobby. Every December, he puts on a holiday display. It lights up his entire neighborhood. Adam’s display is a favorite of many neighbors. His display even has its own Facebook page. It takes Adam all year to plan for it.

All of the lights are powered by electricity. Electricity is the flow of electrons through a conductor. Holiday lights are powered by electricity. Remember that all matter is made of atoms. Atoms are tiny particles too small to be seen.

Atoms are made up of even smaller particles. Electrons are one kind of these smaller particles. Electrons have a negative charge (-). They are in constant motion around the nucleus.

Conducting Electricity

In some kinds of matter, electrons can move from one atom to another. Materials that allow electrons to pass through are electrical conductors. In conductors, the electrons all move in the same direction as one another.

Metals are common conductors. Silver, copper, bronze, and aluminum are all metals. They are good electrical conductors. Scientists can control electricity by passing electrons through these materials.

Some materials don’t allow electrons to pass through. These materials are electrical insulators. Glass, rubber, plastic, and ceramic are all good insulators.

Think about the cord that you plug in to turn on holiday lights. The wire inside the cord is metal. The outer part of the cord is plastic or rubber. This keeps the electricity moving through the wires. It also protects you from an electric shock.

When electricity reaches a light, the light turns on. This is because the moving electrons transfer electrical energy through a circuit. A circuit is the circular path that electrons travel in a negative to positive direction.

All circuits have the same basic parts. All circuits have an energy source such as a battery. The battery has stored chemical energy that converts to electrical energy. This energy provides the force that pushes the electrons in the conductive material through the circuit.

All batteries have a negative end and a positive end. Electrons travel from the negative end through the circuit to the positive end. They move because the negatively charged electrons are attracted to the positive side of the battery. This attraction pulls the electrons toward the positive side of the battery.

Circuits also have wires. Wires are the paths that electrons travel in the circuit. Energy moves from the battery through the conductors inside the wires.

The wires in a circuit are attached to an object that can convert electrical energy to do work. Work is any change in position, speed, or state of matter due to force. For example, a light bulb is an object that does work. When electrons reach the light bulb in a circuit, they transfer electrical energy. The light bulb changes the electrical energy into light energy and heat. The same amount of energy that was transferred through the circuit is available to light up the bulb. This is because of the conservation of energy. The electrons then continue on their path. They return to the opposite side of the battery.

All circuits must include something that can do work. Without this part, the electricity will cause danger by overheating the circuit. This is called a “short circuit.”

Finally, most circuits have switches. The switch opens and closes the circuit. Electrons flow when a circuit is closed. This is “on.” A closed circuit will cause the light bulb to light up. Electrons cannot flow when a circuit is open. This is “off.” No work can be done in an open circuit.

The way a circuit is put together affects the amount of electric current that can do work. Current is a measure of the rate that electric charge passes through a point in an electric circuit over time. In other words, it is the amount of electrons flowing through a circuit over time. The amount of work that can be done increases as current increases. For example, a fast current will cause a light bulb to be brighter than a slow current. This is because more electrons reach the bulb in the same amount of time. Current is measured in amps (A). An electric current with higher amps has more power.

## Hands-on Science Activity

For the hands-on activity of this lesson, students figure out the phenomena of electrical energy’s behavior in series and parallel circuits as they measure how electrical current is affected by the work in a series circuit compared to a parallel circuit. Student teams build series and parallel circuits to do work, collecting data by measuring the amount of current that moves through each circuit at different points, configurations, and workloads. They use their experiment’s data to support an argument about how the phenomena of electrical circuits transfer energy through different types of electric circuits.

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• Vocabulary Check
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• Concept Check Assessment
• Concept Map Assessment
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