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Lesson

Introduction to Electricity

A tiny shock from a doorknob and a giant bolt of lightning are the same thing at very different sizes. Both come from charges that build up and then move.

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Driving Question
Why do you get a shock after dragging your feet across a carpet, and what does that have to do with lightning?
🔬 Learning Science Focus 🔍 Phenomenon First 🧠 Chunked Content 🖼️ Dual Coding ✅ Retrieval Practice 📊 Cause & Effect

What You'll Be Able to Do

By the end of this lesson, you will be able to:

I can describe electricity as a form of energy carried by electric charges, and compare static and current electricity.
7.MS-PS2-3
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I can explain how gaining or losing electrons makes an object positively or negatively charged.
7.MS-PS2-3
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I can predict whether two charged objects will attract or repel, and describe how charge size and distance affect the force.
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I can use evidence to argue that charged objects exert forces on each other even when they are not touching.
7.MS-PS2-5
📚 Instructional Design
Why this section exists
  • State what students will be able to do.
  • Set a clear target before content begins.
Cognitive science
  • Goal setting
  • Advance organizers
Bloom's / DOK
  • Understand to Analyze
  • DOK 1 to 3
Accessibility considerations
  • Plain "I can" statements
  • Standard code shown for reference
  • Short, scannable cards

Words You'll Meet

Choose a card to see what each word means.

📚 Instructional Design
Why this section exists
  • Front-load the terms students will meet.
  • Lower the language barrier before reading.
Cognitive science
  • Pre-teaching vocabulary
  • Reduced extraneous load
Bloom's / DOK
  • Remember to Understand
  • DOK 1
Accessibility considerations
  • One card open at a time
  • Click to reveal, no hover
  • Plain, short definitions

Zap! Where Did That Come From?

You shuffle across a carpet in socks, reach for a metal doorknob, and snap, a tiny spark jumps to your hand before you even touch it. The same kind of event, scaled up, lights the whole sky during a thunderstorm.

Real World Phenomenon

A Spark Across the Gap

Nothing about your finger or the doorknob looks electric. Yet a spark crosses the air between them, and you feel a pinch. No batteries, no wires, no outlet. Lightning does the exact same thing between a cloud and the ground, only millions of times larger. So where does this hidden energy come from, and how can it leap across a gap with nothing touching?

Static shock Finger Doorknob Lightning - - - + + +
A doorknob spark and a lightning bolt are the same event at two very different sizes.
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Make a prediction: What causes the shock when you touch a doorknob after walking across a carpet?
Here's the big idea

The best answer is B. Rubbing your feet on the carpet moves tiny particles called electrons onto your body. That extra charge builds up until it has somewhere to go. When your hand gets close to the metal doorknob, the charge jumps the gap as a spark. To understand the shock and the lightning, we have to look at what charges are and how they move. That is exactly where this lesson goes next.

Where we're headed: First we'll sort out the two kinds of electricity. Then we'll zoom inside the atom to find the charges, learn the rules they follow, and finally connect it all back to that spark across the gap.
📚 Instructional Design
Why this section exists
  • Anchor the lesson in a familiar phenomenon: a static shock.
  • Raise a question students will want answered.
Cognitive science
  • Curiosity gap
  • Phenomenon-based learning
Bloom's / DOK
  • Understand
  • DOK 2
Accessibility considerations
  • Concrete, familiar examples
  • Short framing text
  • Visual anchor

One Idea to Keep in Mind

Here is the one idea electricity depends on. All matter is made of atoms, and atoms are made of protons, neutrons, and electrons. Electricity is all about those charged particles, especially electrons, moving from place to place. That is everything you need to start.

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Extension
The Hidden World of Matter
Optional · Physical Science

Want to go deeper on atoms and their parts before diving in? This optional extension explores the protons, neutrons, and electrons inside every atom. You do not need it to understand this lesson, but it is a great way to see where charge comes from.

Explore →
📚 Instructional Design
Why this section exists
  • State the one supporting idea, atomic structure, that electricity builds on.
  • Keep the lesson self-contained while offering an optional path to go deeper.
Cognitive science
  • Prior knowledge activation
  • Spaced retrieval
Bloom's / DOK
  • Remember to Understand
  • DOK 1
Accessibility considerations
  • Optional and clearly labeled
  • Single, focused review link
  • Plain explanation of why it helps

Two Kinds of Electricity

Electricity is a form of energy made up of electric charges. Those charges can do two different things: they can build up and stay in place, or they can flow. That difference gives us two kinds of electricity.

Energy You Can See, Feel, and Use

Electricity can produce light in a bulb, heat in a toaster, and motion in a fan. All of these come from electric charges. The question is whether the charges are sitting still or moving.

Static Electricity
  • Charge that collects or builds up on the surface of an object
  • The charge stays in place until it has somewhere to go
  • Examples: a shock from a doorknob, lightning
Current Electricity
  • The flow of electric charges through a material
  • Charges move through a conductor such as wire
  • Examples: power lines, computers, appliances
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The key difference: Static electricity is charge that sits and builds up. Current electricity is charge that moves. The doorknob shock is static. The lamp on your desk runs on current. This lesson focuses on static electricity, the kind behind sparks and lightning.
📚 Instructional Design
Why this section exists
  • Sort electricity into two clear categories first.
  • Name where the lesson will focus.
Cognitive science
  • Compare and contrast
  • Category formation
  • Concrete everyday examples
Bloom's / DOK
  • Understand
  • DOK 1 to 2
Accessibility considerations
  • Side-by-side comparison cards
  • Short, parallel bullet lists
  • Familiar examples

Where Charge Comes From

To understand electricity, you have to go very small. All matter is made of atoms, and inside every atom are the charged particles that electricity depends on.

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Parts of an Atom

In the middle of each atom is a nucleus. The nucleus holds two kinds of tiny particles: protons and neutrons. Orbiting around the nucleus are even smaller particles called electrons.

Each particle carries a different charge. Charge is what makes electricity possible.

+ + 0 - - - Nucleus: protons (+) and neutrons (0) Electron (-)
Protons and neutrons sit in the nucleus. Electrons orbit around the outside.
ParticleCharge
Proton+1 (positive)
Neutron0 (neutral)
Electron-1 (negative)
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Electrons are the movers. Protons and neutrons are heavy and stay locked in the nucleus. Electrons are tiny and light, sitting on the outside, so they are the particles that can actually move from one object to another. That movement is the start of static electricity.
📚 Instructional Design
Why this section exists
  • Locate charge inside the atom.
  • Set up electrons as the particles that move.
Cognitive science
  • Builds on the supporting idea of atomic structure
  • Dual coding with the atom diagram
  • Organized comparison table
Bloom's / DOK
  • Remember to Understand
  • DOK 1 to 2
Accessibility considerations
  • Labeled diagram paired with text
  • Simple charge table
  • Key terms defined in place

Neutral, Positive, or Negative?

An object's overall charge depends on one simple count: how many protons it has compared to how many electrons. Move electrons, and you change the charge.

Key idea: Neutral

When the number of protons in an atom equals the number of electrons, the positive and negative charges cancel out. The atom has no overall charge, so it is neutral. For example, 2 protons (+) and 2 electrons (-) add up to no charge.

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Static Electricity Is an Imbalance

Friction can cause electrons to be transferred from one object to another. When you rub two materials together, electrons move. This creates an imbalance of positive and negative charges, and that imbalance is static electricity.

Key idea: Positively Charged

An atom that loses electrons now has more positive protons than negative electrons. With more '+' than '-', the object is positively charged.

Key idea: Negatively Charged

An atom that gains electrons now has more negative electrons than positive protons. With more '-' than '+', the object is negatively charged.

+ + - - Neutral 2 (+) = 2 (-) + + - Positive lost an electron + - - - Negative gained an electron
Lose electrons and an object turns positive. Gain electrons and it turns negative.
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Remember: Protons do not move. Only electrons move. So when an object becomes positive, it did not gain protons, it lost electrons. The charge always comes down to where the electrons went.
📚 Instructional Design
Why this section exists
  • Explain how objects become charged.
  • Correct the common idea that protons move.
Cognitive science
  • Misconception checking
  • Cause-and-effect modeling
  • Dual coding with charged-object diagram
Bloom's / DOK
  • Understand to Apply
  • DOK 2
Accessibility considerations
  • Key terms defined in place
  • Counting model (plus vs minus)
  • Short paragraphs paired with a diagram

Attract or Repel?

Once objects are charged, they push and pull on each other with an electric force. Three simple rules predict what will happen. Click a pairing to see the result.

+ - Attract
+ and -opposite charges
+ and +same charge
- and -same charge
neutral and chargedno charge meets charge
Click a pairing
Will they attract or repel?
Pick two charges above to see how the electric force acts between them. Watch the arrows and the result in the diagram.
The three rules

Law 1: Opposite charges (a + and a -) attract, pulling toward each other. Law 2: Like charges (two + or two -) repel, pushing apart. Law 3: A neutral object is attracted to both positive and negative objects.

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How strong is the force? The electric force is not always the same size. The larger the charge on the objects, the stronger the push or pull. And the closer the objects are, the stronger the force. Move them far apart and the force gets weaker fast.
📚 Instructional Design
Why this section exists
  • Give students rules to predict attraction and repulsion.
  • Introduce how charge size and distance change force strength.
Cognitive science
  • Rule-based prediction
  • Interactive dual coding
  • Cause-and-effect (charge and distance to force)
Bloom's / DOK
  • Understand to Analyze
  • DOK 2 to 3
Accessibility considerations
  • Click to reveal each pairing, no hover
  • Large click targets
  • Plain statement of each rule

Which Way Do Electrons Move?

When you rub two materials together, electrons move from one to the other. But which way? Scientists made a list, called the electrostatic series, that predicts it.

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Some Materials Hold Electrons Tighter

The electrostatic series ranks materials by how tightly they hold their electrons. As you go down the list, materials hold their electrons more strongly. Materials higher on the list give up their electrons to materials lower on the list when the two are rubbed together.

MaterialHold on Electrons
GlassWeak (gives up electrons)
Human Hair
Wool
Rubber
Foam
Plastic Bags
Ebonite (hard rubber)Strong (takes electrons)
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Example: Rub a rubber balloon on your hair. Hair is higher on the list than rubber, so hair gives up electrons to the balloon. The balloon gains electrons and becomes negative. Your hair loses electrons and becomes positive. Now they attract, and your hair stands up.
📚 Instructional Design
Why this section exists
  • Show that electron transfer is predictable.
  • Connect the series back to charging by friction.
Cognitive science
  • Worked example (balloon and hair)
  • Organized reference table
  • Elaboration on prior section
Bloom's / DOK
  • Apply to Analyze
  • DOK 2 to 3
Accessibility considerations
  • Ranked table with clear ends labeled
  • One concrete, familiar example
  • Short reading load

When Charge Jumps the Gap

Built-up charge does not stay forever. When enough charge collects, it can leap across the air to balance out. That sudden jump is a discharge, and it is the answer to our opening question.

Electrons Leap Across the Air

If there are enough positive charges on one object and enough negative charges on the surface of another, the electrons can jump the air gap between them. That jump is a spark.

This is what happens when you touch metal and feel a shock. The charge that built up on you discharges to the doorknob, even before you fully touch it.

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Lightning is the giant version. Inside a storm cloud, the bottom becomes very negative while the ground below becomes very positive. When the charge is large enough, it discharges as a huge spark we call lightning, jumping the gap between cloud and ground.
- - - - - - - - + + + + + + + + air gap
A storm cloud turns negative, the ground turns positive, and the charge jumps the gap as lightning.
📚 Instructional Design
Why this section exists
  • Resolve the opening phenomenon.
  • Show forces acting across a gap, with no contact.
Cognitive science
  • Closing the curiosity loop
  • Scaling from small (spark) to large (lightning)
  • Dual coding with the lightning diagram
Bloom's / DOK
  • Understand to Analyze
  • DOK 2 to 3
Accessibility considerations
  • Familiar event explained plainly
  • Labeled diagram paired with text
  • Connects new term to a known image

Brain Check

Three quick questions before we put it all together. These are not graded. Pulling answers from memory now will help them stick.

Quick Recall · 1 of 3
Just a quick brain check. Not graded.
You rub two materials together and electrons move from one to the other. What builds up?
Quick Recall · 2 of 3
Just a quick brain check. Not graded.
An atom loses some of its electrons. What is its charge now?
Quick Recall · 3 of 3
Just a quick brain check. Not graded.
Two objects both have a negative charge. What will the electric force between them do?
📚 Instructional Design
Why this section exists
  • Strengthen memory through retrieval before the wrap-up.
  • Surface misconceptions early.
Cognitive science
  • Retrieval practice
  • Generation effect
  • Productive struggle
Bloom's / DOK
  • Understand to Apply
  • DOK 1 to 2
Accessibility considerations
  • Ungraded and low stakes
  • Immediate feedback
  • Short tasks reduce load

From Carpet to Lightning

You started with a question: why do you get a shock after walking across a carpet, and what does that have to do with lightning? Now you can trace the whole chain, step by step.

It Starts With Electrons
Friction moves electrons from one object to another.
Rubbing transfers tiny electrons. Lose them and an object turns positive. Gain them and it turns negative. This imbalance is static electricity.
Charges Push and Pull
Opposite charges attract, like charges repel.
Charged objects exert an electric force on each other, even across a gap. The bigger the charge and the closer the objects, the stronger the force.
The Charge Jumps
When enough charge builds up, it discharges as a spark.
Electrons leap the air gap to balance the charge. A small jump is the doorknob shock. A giant jump between cloud and ground is lightning.
The full chain:
Friction moves electrons Objects become positive or negative Charges attract or repel Charge builds up Spark or lightning
The shock from a doorknob and a bolt of lightning are the same physics. Both come from charged particles that build up and then move. Charged objects can even push and pull on each other without ever touching.
📚 Instructional Design
Why this section exists
  • Tie the pieces into one cause-and-effect chain.
  • Answer the opening question directly.
Cognitive science
  • Schema building
  • Elaboration
  • Coherent narrative
Bloom's / DOK
  • Understand to Analyze
  • DOK 3
Accessibility considerations
  • Step-by-step beats
  • Plain causal language
  • Builds on prior sections

Check Your Understanding

Ten questions covering everything you explored, from static and current electricity to the law of electric charges. Answer every question, then submit.

Your score will not be sent Your score will be sent to your teacher
0 / 10 selected
🧠 Show Your Thinking

Scientists don't just know the answer. They explain their thinking.

Write your own explanation first. Then submit your work to compare your thinking with a model answer.

In one or two sentences, explain how dragging your feet across a carpet can lead to a shock that jumps to a doorknob before you even touch it. Trace what the electrons do, from the carpet to the spark. Use the word electrons.

One strong way to say it Rubbing your feet on the carpet transfers electrons onto you, so you build up an extra charge. That static charge stays on you until it has somewhere to go. When your hand gets close to the metal doorknob, the built-up electrons jump the air gap as a spark, even before you touch it. That sudden jump is a discharge, and lightning is the same thing between a cloud and the ground on a giant scale. If your sentences follow the electrons from the carpet, onto you, and across the gap, you have it.
📚 Instructional Design
Why this section exists
  • End the lesson with the student constructing the causal chain in their own words, not selecting it.
  • Give the one place where the student generates rather than clicks.
Cognitive science
  • Generation effect and self-explanation
  • Cause-and-effect: tracing electrons from friction to discharge
  • Self-check reveal for comparison, ungraded
Bloom's / DOK
  • Analyze to Evaluate
  • DOK 3
Accessibility considerations
  • Sentence-length response, not an essay
  • Keyword scaffold ("electrons")
  • Model answer to compare against

🔍 The Question You Came In With You started this lesson asking: "Why do you get a shock after walking across a carpet, and what does that have to do with lightning?" If you can trace friction to electron transfer to charge to discharge, you have answered it.
📚 Instructional Design
Why this section exists
  • Check understanding against the lesson goals.
  • Give students and teachers a clear signal.
Cognitive science
  • Retrieval practice
  • Feedback loops
Bloom's / DOK
  • Understand to Apply
  • DOK 1 to 2
Accessibility considerations
  • Answer explanations provided
  • Practice and classroom modes
  • Plausible, evenly placed options

More Learning

The lesson is just the beginning. Dig deeper into static electricity, current electricity, and the law of electric charges that explains sparks and lightning. More investigations, simulations, and challenges are coming soon.

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More Coming Soon
The lesson is just the beginning. More investigations, simulations, and challenges are coming soon.
Coming Soon
📚 Instructional Design
Why this section exists
  • Offer pathways beyond the core lesson.
  • Signal that learning continues past the quiz.
Cognitive science
  • Interest-driven extension
  • Transfer to new contexts
Bloom's / DOK
  • Apply to Analyze
  • DOK 2 to 3
Accessibility considerations
  • Optional and self-paced
  • Clear labels for what is available
  • No penalty for skipping