# Current Electricity

In this unit, students continue to explore science phenomena related to energy, focusing on how energy is transferred in circuits and can do work, such as spinning a motor. Students begin with this lesson on exploring the basic phenomena of direct current energy flowing through parts of a simple and series circuit. This page demonstrates components of this lesson on current electricity.

## Science Background for Teachers:

Science background provides teachers with more in-depth information about the phenomena students explore in this unit about electrical energy.

A circuit must be complete and unbroken to function properly. If there is a break in the circuit, it is open and the electricity cannot move. The air between the open part of the circuit will not conduct or transport the electrons. The wire must be closed to restart the electron flow. There are four main parts of a circuit.

1. A battery is a source of energy that pushes electrons through a circuit. Batteries hold stored chemical energy that can be turned into electrical energy when they are put into circuit. The battery provides the force that pushes the electrons 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. The negatively charged electrons are attracted to the positive side of the battery, and this attraction pulls the electrons toward the positive side of the battery. As the electrons move, they carry electrical energy.

2. Wires create a path of conducting material for electrons to travel. Energy moves from the battery through the conductive wires.

3. The wires in a circuit are attached to an object that can convert the electric energy to do work (any change in position, speed, or state of matter due to force). For example, a motor is a machine that converts an input of energy into an output of kinetic energy. When a motor is part of a circuit, the electrical energy is converted into kinetic energy, making the motor spin. All circuits must include something that can do work. Without this part, the electricity will cause danger by overheating the circuit, causing a short circuit.

4. A switch opens and closes a circuit to control electron flow. Electrons flow when a circuit is closed (on). Electrons cannot flow when a circuit is open (off).

There are different ways that circuits can be designed. For example, a simple circuit has one path and one object that can do work.

A series circuit uses one path but has more than one piece of work in the path of the same electrons. This means in a series circuit with two light bulbs, the electricity moves from one light bulb to the next before it returns to the energy source. If one bulb stops working, it breaks the circuit so the electricity cannot continue on its path.

Both simple and series circuits powered by batteries use a kind of electric current called direct current. Direct current (DC) is electric current that is constantly flowing in one direction from a negative to a positive charge.

Batteries always create a direct current because the electrons always flow from the negative side to the positive side. DC is useful for carrying electricity over short distances. In this unit, students will observe direct current in all of their circuits.

Alternating current (AC) is electric current that changes its direction many times every second. Alternating current is easier and cheaper to send over long distances, so power plants use it to send electricity to homes.

## Science Lesson: Exploring Current Electricity

In this lesson, students build simple and series circuits to observe how energy can be transferred from one place to another via electric currents. They then analyze how the flow of current electricity through a circuit can change direction depending on the configuration of the circuit with the battery.

## Science Big Ideas

• Energy can be transferred from one place to another through electric currents in a circuit which has four basic parts.
• Electricity is all around us. It powers lights, computers and other electronic devices, appliances such as refrigerators, and televisions.
• Electricity is the movement of electrons through a conductor. Electricity can be controlled when it moves through a circuit, which is the circular path that electrons travel in a negative to positive direction.
• There are two types of current electricity: direct current and alternating current. Direct current is electric current that is constantly flowing in one direction from a negative charge to a positive charge. Alternating current is electric current that changes its direction many times every second.
• A circuit needs wires to conduct electricity. The wires must be conductive. Wires are often made of some kind of metal, which is a good conductor.

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## Science Essential Questions

• How is the structure of matter connected to electricity?
• Why do all circuits need an energy source such as a battery?
• What makes the electrons move in the same direction as one another?
• What part does a circuit have to have so that electrons can travel?
• Do a circuit’s wires need to be conductors or insulators?
• Why are circuits helpful to people?
• How do circuits convert energy from one form to another?
• Why is it important that a circuit always includes something that can do work?
• Why do batteries generate direct current?
• How is an alternating current different from a direct current?
• Why is it beneficial to have alternating current?

## Common Science Misconceptions

Misconception: The wires in a circuit are like empty pipes that electricity flows through.
Fact: Like all matter, the wires are themselves made up of atoms. These atoms have electrons that begin to move when the battery or other energy source pushes them through the circuit.
Misconception: Energy flows in a circular motion in a circuit, returning to the energy source.
Fact: Electrons travel in a circular path, returning to the energy source. Energy is transferred from the energy source to the object doing work. The electrical energy is then converted to another form of energy to do work.

## Science Vocabulary

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

Direct Current:  electric current that is constantly flowing in one direction from a negative to positive charge

Electricity:  the flow of electrons through a conductor

Electric Conductor – a material that allow electrons to pass through

Electric Insulator – a material that electrons cannot pass through easily

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

Adriana’s sister is already asleep in their bedroom. The room is dark. But Adriana isn’t tired. She’s in the middle of an exciting chapter in her book.

Adriana covers herself with her bed covers. She turns on her flashlight. She keeps reading. Time passes. The flashlight bulb gets dimmer. After a while, the light shuts off completely. Adriana has to stop reading.

The flashlight won’t turn on again until Adriana puts new batteries into it. Flashlights need batteries to function.

Electricity and Matter

The flashlight needed new batteries because batteries are a source of energy. Batteries hold stored chemical energy. This energy turns into electrical energy when the batteries are put into a device such as a flashlight.

Flashlights use the energy in the batteries to produce electricity. Electricity is the flow of electrons through a conductor.

Electricity happens because of the atoms that make up all matter. Remember that atoms are tiny particles too small to be seen. They are made up of even smaller particles. Electrons are one kind of these smaller particles. Electrons have a negative charge (-).

Conducting Electricity

In some kinds of matter, electrons can move from one atom to another if they are given a push of energy from an outside source. Materials that allow electrons to pass through are electrical conductors. Electrons always move in the same direction as one another in an electric current.

Metals are common conductors. Silver, copper, bronze, and aluminum are all metals. They are good electrical conductors.

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

Electricity in a Flashlight

The energy stored in the batteries powers the flashlight because there is a circuit inside the flashlight. 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 batteries. The battery 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. A “dead” battery is one that can no longer pull electrons.

Circuits also have wires. Wires are the paths that electrons travel in the circuit. As they travel, the electrons carry electrical energy from the battery. Energy moves from the battery through the conductive 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. A motor is another example of an object that does work. A motor is a machine that converts an input of energy into an output of kinetic energy. When a motor is part of a circuit, it changes the electrical energy into kinetic energy.

## Hands-on Science Activity

In this lesson, students explore the phenomena created by electrical energy traveling through circuits with motors by analyzing how the flow of current electricity through a circuit can change direction and how this affects the work done by the electrons. Students create diagrams of their circuits to visualize how the different parts work together to transfer energy through electric currents to do work (spinning the motor). Students collect and analyze observational data to explain why reversing the direction that electrons flow through a circuit affects the work being done.

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• Vocabulary Check
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