Make and Use an Electromagnet, Grade 8
It works or it does not, and the whole class can see which.
The Grade 8 electromagnet project is the one assessed task of the year that a learner has to bring to school and demonstrate. Ten of its thirty marks are awarded while you stand there holding it, picking up nails in front of the teacher. A coil wound carelessly, or a cell flattened the night before, lifts nothing at all.
So this page is written to make it work on the day, and to give you something to measure: how many nails it lifts at 20, 40 and 60 turns.
Where this fits in the curriculum
| Subject | Natural Sciences |
|---|---|
| Grade | 8 |
| Term | 3 |
| Strand | Energy and change |
| Topic | Energy transfer in electrical systems |
| Status | CAPS project, formally assessed |
| Marks | 30: ten for the demonstration, twenty for the questions. Our worksheet adds thirty of our own |
What you need
| For the electromagnet | For the circuit |
|---|---|
| One long iron nail, 75 mm or longer | One or two cells |
| At least 2 m of insulated copper wire | Conducting wire |
| Wire strippers, or sandpaper | A small bulb |
| Insulation tape | A switch you made yourself |
And the thing every equipment list leaves out: about twenty small iron nails to pick up. The demonstration is marked on them. Panel pins or 25 mm wire nails are ideal, and steel paper clips work too.
How to make an electromagnet
- Bare about 3 cm at both ends of the wire. How you do that depends on the wire, and this is where most projects fail. See below
- Wind the wire onto the nail, neatly, all in the same direction. Leave both ends free
- Tape the coil so it cannot unwind
- Build the circuit: cells, your switch, the bulb and the coil, all in one loop
- Close the switch. The bulb should light
- Hold the head of the nail over the small nails and lift. Move them, then open the switch and they drop
The mistake that kills most projects: the wrong way to bare the wire
Two completely different wires are sold as "insulated copper wire".
| Wire | How to bare the ends |
|---|---|
| PVC covered, with a thick coloured plastic sleeve | Wire strippers. About 3 cm at each end |
| Enamelled, thin and orange-brown, looks like bare copper already | Sandpaper. Rub all the way round until the copper shines |
Wire strippers do nothing to enamelled wire. The coating is a varnish, not a sleeve. A learner strips it, sees shiny copper, connects it, gets no current at all, and concludes the project cannot be done. If your bulb will not light, this is the first thing to check.
Why all the turns must go the same way
Every turn of wire makes its own small magnetic field. Wound the same way, they add together. Wound back the other way, they cancel.
Ten turns one way and ten the other gives you an electromagnet that lifts nothing, and the coil looks perfect. Neat, touching turns, one direction, one or two even layers.
Why the bulb is really there
The project asks you why the bulb is necessary, and most answers say "to show the current is flowing". That is half of it.
Two metres of copper wire has almost no resistance. Connected straight across a cell, the coil is close to a short circuit. The cell gets hot, goes flat in minutes and can leak.
The bulb limits the current to something the cell can survive. It is a safety device and an indicator at the same time, and that is worth writing in your answer.
Making the switch
It has to be home made. The version that always works: push two drawing pins into a piece of card or a matchbox, hook a steel paper clip under one so it swings, and swing it onto the other to close the circuit.
Our addition: measure it
The project says more wire makes it stronger and never asks for a number. So take one.
- Wind 20 turns. Lift the small nails three times and record the best
- Add 20 more turns and repeat
- Add 20 more and repeat again
| Turns | Typical lift on 3 V |
|---|---|
| 20 | 1 to 3 nails |
| 40 | 4 to 8 nails |
| 60 | 8 to 15 nails |
Three lifts at each stage, and take the best, because how the nails happen to be lying matters as much as the magnet does.
Your graph should rise and then flatten. More turns means more field, but the longer wire also has more resistance, so the current drops. Noticing that flattening is worth more than a tidy straight line.
If it does not work
| Problem | Cause | Fix |
|---|---|---|
| The bulb is dark and nothing happens | The enamel is still on the wire ends | Sandpaper until the copper shines all the way round |
| Bulb dark, but the wire is definitely bare | The switch is not making contact, or the cell is flat | Press the clip down firmly. Try a fresh cell |
| The bulb lights but it lifts nothing | The turns are wound in both directions | Unwind and rewind, one direction only |
| It lifts one nail and no more | Too few turns, or a tired cell | Forty turns or more, and two fresh cells |
| The nails stay stuck after the switch opens | The nail has kept a little magnetism | Normal with hard steel. Tap it on the bench, and write it down: it is a real observation |
| The coil gets hot | The bulb has been left out of the circuit | Put it back. The coil on its own is nearly a short circuit |
| It worked at home but not at school | The cells went flat in the bag, still connected | Carry the cells separately and connect them when you arrive |
Safety
- Never connect the coil straight across a cell. The bulb stays in the circuit
- Two AA cells, not a 9 V block, and never mains electricity or a car battery
- Open the switch between tries. Leaving it closed flattens the cells and heats the coil
- The nail can get warm. If it gets hot, open the switch and let it cool
- Tape the cut ends of the wire. They are sharp
- Count the small nails out and count them back. They end up on the floor, and they are a choking risk around small children
How the marks work
| Part | Marks |
|---|---|
| Demonstration, marked while you show it | 10 |
| Questions handed in with the circuit | 20 |
| Prescribed total | 30 |
| Our extra testing section | 30 |
| Our worksheet | 50 |
The biggest single item in the prescribed twenty is the labelled circuit diagram, worth five. It must be a diagram with proper symbols, with the electromagnet drawn as a resistor, not a picture of a nail and a battery.
Free worksheet and marking memo
Both free, no sign up, straight to the PDF.
- Learner worksheet, 50 marks. Part A is the prescribed 20 handed in with the circuit; Part B is our own testing section
- Marking memorandum, with a suggested split for the demonstration 10, what to accept for each answer, and the five answers that look right and score nothing
Related practicals
- Magnetism and magnetic fields. What the field looks like, with iron filings and compasses
- Series and parallel circuits, Grade 9. Where this circuit goes next
- Atoms, elements, compounds and mixtures, Grade 8. Another Grade 8 practical that runs on two cells and some wire
What you need to run it
For one learner, the whole project is a nail and two metres of wire. Our electromagnet school project kit is exactly that, at R56: copper wire and the nail in one packet, which is the part parents struggle to find in project week.
For a class set, a 250 g reel of enamelled copper wire winds a great many nails, and you will want AA battery holders and a pack of crocodile leads so the circuits can be built and rebuilt.
The rest of the range for this topic is in magnetism equipment for schools.