Grade 7 Magnets & Motors worksheet
from Gradelings · Name: ______________________
How to explain it
- Like poles push apart; opposite poles pull together. A compass lines up with Earth’s magnetic field.
- An electromagnet gets stronger with more coils of wire, more current or an iron core.
- A motor changes electrical energy into motion. A generator changes motion into electrical energy.
Example: A wind turbine spins and makes electricity. Is it a motor or a generator? It starts with motion from the wind. It ends with electrical energy. Motion into electricity is a generator. Answer: generator
Question 1
You cut a bar magnet in half. What do you get?
🧲- One north-only magnet and one south-only magnet
- One magnet and one piece of plain iron
- Two smaller magnets, each with its own north and south pole
- Two pieces that are no longer magnetic
Two smaller magnets, each with its own north and south pole
Hint: Every magnet, however small, has both a north and a south pole.
Question 2
Motor or generator? Sort each device.
Sort into: ⚙️ motor (electricity → motion) · ⚡ generator (motion → electricity)
- 🚗electric car wheels
- 🔄ceiling fan
- 🧺washing machine drum
- 🔦hand-crank flashlight
- 🌊hydroelectric dam
- 🪥electric toothbrush
- 🏭steam turbine in a power station
- 🌬️wind turbine
⚙️ motor (electricity → motion): electric car wheels, ceiling fan, washing machine drum, electric toothbrush · ⚡ generator (motion → electricity): hand-crank flashlight, hydroelectric dam, steam turbine in a power station, wind turbine
Hint: A motor turns electrical energy into motion. A generator turns motion into electrical energy.
Question 3
An electric motor changes…
⚙️- chemical energy into heat
- electrical energy into motion
- sound into light
- motion into electrical energy
electrical energy into motion
Hint: Current in a coil makes a magnetic field that pushes against magnets, making the motor spin.
Question 4
A compass needle is a small magnet. What does it line up with?
🧭- Earth's magnetic field
- the nearest mountain
- the position of the Sun
- the direction of the wind
Earth's magnetic field
Hint: Earth acts like a giant magnet. A compass needle turns to line up with its field.
Question 5
Students tested an electromagnet with different numbers of coils. If the pattern continues, how many paper clips would 40 coils pick up?
Electromagnet test: wire coiled around an iron nail Coils of wire Paper clips picked up 10 5 20 10 30 15 answer box
20
Hint: Every 10 coils picks up 5 clips. 40 coils is 4 groups of 10, so multiply 4 × 5.
Question 6
What do electricity and magnetism have in common?
- Both need sunlight to work
- Both only happen in outer space
- Both are caused by gravity
- Both are produced by the electromagnetic force
Both are produced by the electromagnetic force
Hint: Moving charges create magnetic fields, and moving magnets create currents: one force, two effects.
Question 7
Which change would make an electromagnet stronger?
- Wrapping more coils of wire around the core
- Using a wooden core instead of iron
- Switching the current off
- Using fewer coils of wire
Wrapping more coils of wire around the core
Hint: More coils, more current, or an iron core all make an electromagnet stronger.
Question 8
What is an electromagnet?
🧲- A magnet that only works underwater
- A magnet made of natural rock
- A battery that stores magnetism
- A coil of wire that acts as a magnet when current flows through it
A coil of wire that acts as a magnet when current flows through it
Hint: Electric current flowing in a wire makes a magnetic field. Coiling the wire makes the field stronger.
Question 9
What happens to an electromagnet when the current is switched off?
- Its poles get stuck forever
- It becomes twice as strong
- It turns into a battery
- It loses most of its magnetism
It loses most of its magnetism
Hint: The magnetism comes from the current. No current means (almost) no magnetic field.
Question 10
Where is the magnetic field of a bar magnet strongest?
- exactly in the middle
- evenly everywhere along it
- at its poles (the ends)
- far away from the magnet
at its poles (the ends)
Hint: Sprinkle iron filings around a bar magnet: they bunch up most at the two ends.
Answer key
- 1. Two smaller magnets, each with its own north and south pole
- 2. ⚙️ motor (electricity → motion): electric car wheels, ceiling fan, washing machine drum, electric toothbrush · ⚡ generator (motion → electricity): hand-crank flashlight, hydroelectric dam, steam turbine in a power station, wind turbine
- 3. electrical energy into motion
- 4. Earth's magnetic field
- 5. 20
- 6. Both are produced by the electromagnetic force
- 7. Wrapping more coils of wire around the core
- 8. A coil of wire that acts as a magnet when current flows through it
- 9. It loses most of its magnetism
- 10. at its poles (the ends)
Want more than 10 questions?
In Gradelings the questions change every time and adjust to your child, with hints and kind feedback.