Young Inventors, lesson 2 of 24
Basic Safety for Young Engineers: how to work with electricity safely
Introduction
Why can you touch both ends of a torch battery and feel nothing, but you must never poke anything into a wall socket? Both have electricity inside. The difference is how hard that electricity pushes.
In this lesson you'll learn which electricity is safe for your experiments, why some of it is dangerous, and the golden rules that keep every engineer safe, from beginners to experts.
Working principle
Your body can carry electricity, a bit like a wire can. When electricity flows through your body, that's called an electric shock.
How much flows depends on the push, called voltage and measured in volts (V):
- A torch battery pushes with 1.5 V. A square battery pushes with 9 V. That's too gentle to push electricity through dry skin, so you won't feel it.
- The wall socket in an Indian home pushes with about 230 V. That's more than 25 times stronger than a 9 V battery. It can push enough electricity through your body to stop your heart.
Dry skin is like a thick wall that slows electricity down. Wet skin is like an open door, so electricity flows through much more easily. That's why we never work with wet hands.
Even small batteries can be dangerous in other ways:
- If you connect a battery's + and − directly with a wire, that's called a short circuit. Lots of current rushes through, the wire and battery get very hot, and some batteries can leak or even catch fire.
- Button batteries (the small round coin ones) are very dangerous if swallowed. Keep them away from little brothers and sisters, and pets too.
What you'll need
Your safety kit for every project:
- A grown-up nearby when you build, especially the first few times
- Batteries (AA, AAA or 9 V) and a battery holder, never a wall socket
- A clear, dry table, away from water and drinks
- Safety glasses for cutting wires or using tools
- Tools with plastic handles, like wire strippers and small screwdrivers
Working in real life
These are the golden rules. Read them out loud before your first build.
Before you start
- Ask a grown-up to be with you, so they can help and see what you make.
- Check your wires. If the plastic cover is cracked and you can see metal inside, don't use it. Ask for a new one.
- Dry your hands and clear the table.
While you build
- Keep the battery unplugged while you connect or change wires. Connect the battery last, like turning on a tap only after the pipes are connected.
- Before you connect the battery, check every connection twice. A wrong connection can burn out a part, like an LED.
- Never join the battery's + and − directly with just a wire.
- If anything gets hot, smells of burning, or starts to smoke, disconnect the battery straight away and tell a grown-up.
Things only grown-ups do
- Plugging anything into the wall socket, and opening anything that plugs into the wall: TVs, chargers, computers, microwaves. These can hold dangerous electricity even after they're unplugged.
- Using a soldering iron. It gets hotter than a cooking pan.
When you finish
- Disconnect the battery and put everything back in its box. Store button batteries where small children can't reach them.
Try it
Be a safety inspector. Look at the place where you'll do your experiments and check:
- Is the table dry, with no drinks on it?
- Do you have batteries ready, so you won't need a wall socket?
- Are all your wires in good condition?
- Who is the grown-up who will help you?
When you can answer yes to all four, your workbench is ready.
Check what you learnt
Which of these is safe to use for your experiments?
When should you connect the battery to your circuit?
Your circuit starts to feel hot and smell funny. What do you do?
Conclusion
- Small batteries push gently, like a garden hose. The wall socket pushes hard, like a fire hose, so it's for grown-ups only.
- Build first, check twice, and connect the battery last.
- If something gets hot or smells of burning, disconnect the battery and tell a grown-up.
What next?
Now meet the safe power source you'll use in every project: What is a Battery?