C. Matter and Energy · Electrical Phenomena, Energy, and Devices

Current Electricity: Charges on the Move

C2.2 A1.4 A1.5About 40 minutes

Learning goals

I can describe current electricity as a steady flow of electric charge through a closed path.
I can explain why current electricity needs an energy source, such as a battery.
I can compare and contrast current electricity with static electricity.
I can explain why batteries are safe to explore with but wall outlets are not.

Words to know

current electricity
A steady flow of electric charge (electrons) through a closed path.

electric current
The flow of electric charge through a conductor, such as a wire.

circuit
A complete, closed path that electric current can flow around.

battery
A device that stores chemical energy and changes it into electrical energy to push current around a circuit.

terminal
One of the two ends of a battery where wires connect: positive (+) and negative (−).

volt (V)
The unit that tells how strongly a battery or other source pushes the current. An AA battery is 1.5 V.

Two kinds of electricity

The zap from a doorknob lasts a split second. But the lamp in your bedroom can glow all evening, and a flashlight keeps shining on a winter camping trip until its batteries run out.

Both are electricity, but they behave very differently. The zap is static electricity. The lamp and flashlight use current electricity. In this lesson you will find out what makes them different, and what they have in common.

A dome tent glowing in a snowy pine forest at dusk, with a lit flashlight on the snow. — A flashlight keeps shining as long as current flows from its batteries, which is very different from a quick static zap. AI-generated image

What is current electricity?

Current electricity is a steady flow of electric charge. In wires, the charges that flow are electrons.

The electrons flow through conductors, like the metal inside a wire.
They need a complete, closed path to flow around. This path is called a circuit. If there's a gap anywhere in the path, the flow stops.
They need an energy source to push them, like a battery or a power station's generator. A battery changes chemical energy into electrical energy.

A bike-chain model. Think of the electrons in a wire like the links of a bike chain. When you push the pedals (the battery), the whole chain starts moving at once, all the way around. That's why a light turns on the instant you flip the switch, even though each electron only creeps along slowly. If the chain breaks (a gap in the circuit), nothing moves.

The bike-chain model. The battery is like the pedals: it pushes all the electrons around the loop at once, so the bulb lights the instant the circuit is closed.

Batteries and volts

Every battery has two ends called terminals: positive (+) and negative (−). Electrons flow out of the negative terminal, around the circuit, and back into the positive terminal.

The volt (V) tells how strongly the battery pushes the current.

An AA or AAA battery: 1.5 V
A rectangular 9 V battery: 9 V
A wall outlet in a Canadian home: 120 V. That is 80 times the push of an AA battery, and it can seriously hurt or kill a person.

That is why all the experiments in this unit use only small AA, AAA or 9 V batteries, never wall outlets.

Comparing the push (voltage) of each source. A wall outlet's 120 V is 80 times an AA battery's 1.5 V, which is why experiments use small batteries only.

	Static electricity	Current electricity
What is it?	Charge that builds up on the surface of an object	Charge that flows steadily through a path
Does the charge move?	It stays put, then moves suddenly all at once (a discharge)	It moves continuously, as long as the circuit is complete
How is it made?	Rubbing two different materials together	An energy source, like a battery or a generator
Path needed?	No path needed to build up	Needs a closed circuit of conductors
Builds up on / flows through	Usually insulators like rubber, plastic, wool	Conductors like copper wire
Can we control it?	Hard to control	Easy to control with a switch
Useful for	Some jobs, like photocopiers and air cleaners, and fun experiments	Powering lights, fridges, computers, furnace fans and much more
Examples	Doorknob zap, clingy clothes, lightning	Flashlight, phone, toaster, streetlights

Comparing and contrasting static and current electricity.

What they have in common

Static and current electricity are both made of electric charges (electrons). Both can give off light, heat and sound (a spark crackles and glows; lightning flashes and causes thunder; a bulb glows). And both can be dangerous in large amounts: lightning and wall-outlet electricity can both kill.

Worked example

Let's compare a doorknob zap and a flashlight

Use the words build up, flow, circuit and energy source to compare a doorknob zap with a flashlight.

Doorknob zap: charge builds up on your body when you walk on carpet. It's made by rubbing (your socks on the carpet). There's no circuit.
When you touch the doorknob, the charge jumps once, in a split second. It's static electricity.
Flashlight: the batteries are an energy source. When you slide the switch on, you complete a circuit.
Electrons flow steadily through the circuit, so the bulb shines for as long as the switch is on and the batteries have energy. It's current electricity.
Same: both involve moving electric charges, and both give off light (the spark and the bulb).

The zap is static electricity: charge builds up by rubbing and discharges once. The flashlight is current electricity: a battery pushes a steady flow of charge around a closed circuit.

Just for fun

Funny but true: each electron in a wire only creeps along, often slower than a snail! The light still turns on instantly, because the whole "chain" of electrons starts moving at once.

Hands-on activity

Flashlight detective

You need: a flashlight that uses AA or AAA batteries, and a grown-up.

Turn the flashlight on and off. Predict: where does the current flow?
With a grown-up, open the battery compartment. Look at how the batteries sit. Find the + and − marks on each battery and inside the flashlight.
Look for the metal strips and springs that touch the battery ends. Trace with your finger the path from the battery, through the metal parts, to the bulb and back.
Test: take out one battery. Does the light work? Put it back the right way. Now turn one battery around (backwards). Does it work? Put it back the right way.
Draw a labelled picture of the path the current takes.
Share it (A1.5): make a Venn diagram (two overlapping circles) comparing static and current electricity. Put at least 3 ideas in each part.

What to look for: the light only works when the batteries are in the right way and there is a complete metal path. Removing a battery leaves a gap, so no current flows. In most flashlights, one battery turned backwards stops the light, because the two batteries push in opposite directions.

Safety (A1.4): never open, cut or bite a battery, and never use one that is leaking, swollen or damaged. Do not take apart anything that plugs into the wall. Wash your hands after handling batteries.

Your turn

What is current electricity?

What two things does current electricity need in order to flow?

What energy change happens inside a battery when it is used?

How many volts is an AA battery? How many volts is a Canadian wall outlet?

Give one way static and current electricity are alike.

Give two ways static and current electricity are different.

More practice: warm-up

Static or current? A toaster heating your bread.

Static or current? Your socks crackling as you pull them apart.

Static or current? Lightning.

Static or current? A phone playing music.

What are the two ends of a battery called?

More practice: on your own

Why does a light turn on the instant you flip the switch, even though electrons move slowly?

Why is current electricity more useful than static electricity for running a fridge?

Why do we only use AA, AAA or 9 V batteries for experiments?

A flashlight won't turn on. One of its batteries was put in backwards. Explain why it doesn't work.

Electrons in a circuit flow out of which battery terminal and back into which?

Challenge

Lightning is static electricity, but it gives off a huge amount of energy. Use the comparison table to explain why we can't easily use lightning to power homes.

Zoe says, "Static electricity and current electricity are completely different things." Do you agree? Give one similarity and one difference to support your answer.

A 9 V battery has the same push as how many AA batteries together? A wall outlet (120 V) has the same push as how many AA batteries?

Check your understanding

Quiz

Current electricity is...

Which of these is current electricity?

What does a battery do in a circuit?

How is static electricity different from current electricity?

A Canadian wall outlet is about...

What do static and current electricity have in common?

For parents and teachers

Big idea (C2.2): describe current electricity (a continuous flow of charge through a closed circuit, driven by an energy source) and compare and contrast it with static electricity. The flashlight investigation and Venn diagram support safe investigation (A1.4) and communication (A1.5).

How to help: use the flashlight as your model all unit. Ask: "Where does the current go? What happens if there's a gap?" Have your child explain the bike-chain model in their own words.

Common difficulties:

Thinking electricity is "used up" in the bulb. The charge flows all the way around and back to the battery; it's the battery's energy that gets used up.
Thinking electrons race through the wire at high speed. The flow starts everywhere at once, like a bike chain, which is why lights come on instantly.
Saying static and current are completely different. Both are electric charge; the difference is whether it builds up or flows.

Note on direction: many diagrams show current flowing from + to − ("conventional current", chosen before electrons were discovered). Electrons actually flow from − to +. Either is fine at this level as long as your child knows the path must be complete.

Safety: experiments in this unit use only AA, AAA or 9 V batteries. Never let children experiment with wall outlets, plugs or extension cords. Never open, cut or bite batteries; keep button/coin batteries away from young children (they are dangerous if swallowed).