Flow of electricity
Flow of electricity
- Unit 1: Particles & Pressure
- Unit 2: Forces & Motion
- Unit 3: Energy & Heat
- Unit 4: Electricity
- Unit 5: Magnetism & Electromagnetism
- Unit 6: Waves: Sound & Light
- Unit 7: Scientific Investigations
In this topic you will:
- understand how electricity flows around a circuit
- learn about the electrons that flow to make electric current.
Key Words
attract, battery, cell, components, current, electrons, free to move, negative charge, repel, terminals
Current
Look at the circuit in the picture.
When you close the switch, the lamp lights.
A cell stores chemical energy that can be changed to electrical energy in a circuit. A battery contains two or more cells joined together.
The cell in the circuit has two connections, called terminals.
All cells, batteries, power supplies and many other components have two terminals.
The terminals are labelled with + and − symbols, meaning positive (+) and negative (−).
You can see these symbols in the photograph of these three cells.
The photograph below shows one of the batteries from an electric car. You can see that the battery is made from many cells.
When connected into a circuit, the negative terminal of a cell, battery or power supply pushes electrons around in the wires.
All materials contain atoms. Atoms contain smaller particles. An electron is one type of smaller particle in an atom.
The flow of electrons in the circuit is called current.
Important Concept
The movement of electrons through a circuit is what causes electric current to flow. This process begins at the negative terminal and flows toward the positive terminal through conducting materials like wires.
More about electrons
Some of the electrons in a metal are free to move. That means they can move through the metal.
In a metal, these electrons move randomly, as shown in the diagram. Electrons are very small and this diagram is not to scale.
When the metal is placed into a circuit, the electrons move in the same direction.
Right: Electrons are negatively charged so they move toward the positive terminal in a circuit.
Electrons have a negative charge.
Opposite charges attract, and like charges repel. To attract means to pull together and repel means to push apart. That means:
- positive and negative attract
- positive and positive repel
- negative and negative repel
Therefore, electrons will be attracted towards the positive terminal of the power supply and be repelled from the negative terminal.
If there is a break in the circuit, all the electrons stop flowing. Electrons can only flow in a complete circuit.
Quick Fact
Electrons carry a negative charge and are responsible for the flow of current in metallic circuits. They are much smaller than atoms and exist in all conductive materials.
Questions
Show Answer
Electrons
Each word may be used once, more than once or not at all.
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electrons
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negative
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attracted, repelled
Think Like a Scientist
In this task, you will make and test predictions about how electric current flows in a circuit.
• Power supply or battery
• Long wires (over 2 metres) or multiple short wires joined together
• 4 identical lamps that work in series with the power supply
Step 2. Place two more lamps several metres apart further along the circuit.
Step 3. Place the fourth lamp close to the positive terminal.
Do not switch on the power yet.
Show Answer
All lamps should light up at the same time because current flows through the entire circuit instantly once closed.
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Yes, you can test it by switching on the circuit and observing the lamp behaviour.
Show Answer
It is called a hypothesis.
Show Answer
All lamps turned on at the same time regardless of distance from the power supply.
Show Answer
Electrons throughout the circuit start moving together as soon as the circuit is complete, causing all lamps to light at once.
Reflect on:
- What did I learn about how current behaves in a complete circuit?
- Did I use evidence from observation to explain my answers?
- Is there anything I’m still unsure about in circuits?