Electricity and Magnetism — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A magnet made by wrapping wire around iron and running current through it is an electromagnet.
An electromagnet uses the magnetic field made by flowing current through a coil to turn magnetism on and off.
2. A compass has a tiny magnet that lines up with Earth to point North.
A compass needle is a small magnet that aligns with Earth's magnetic field so its north end points toward magnetic north.
3. A junkyard crane uses a huge electromagnet to lift heavy steel cars.
A junkyard crane turns the electromagnet on to grab steel, then turns it off to drop the load exactly where workers want.
4. The two ends of a bar magnet are called the north and south poles.
Every magnet has a north pole and a south pole where the magnetic force is strongest.
5. Two north poles pushed together will repel each other.
Like poles, such as two norths, push apart because their magnetic fields point against each other.
6. A north pole and a south pole will attract each other.
Opposite magnetic poles pull toward each other because their magnetic fields line up and join smoothly.
7. Turning off the current in an electromagnet makes its magnetism stop.
An electromagnet only has a magnetic field while current flows; cut the current and the magnetism stops.
8. A refrigerator magnet sticks to the door because the door is made of steel.
Refrigerator doors are made of steel, which contains iron and is strongly attracted to magnets.
9. An electromagnet is stronger when you add more loops of wire around the iron.
Adding more turns of wire creates a stronger magnetic field because each loop adds to the total magnetism.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Compass
→ Points toward magnetic north
Lifts heavy steel in a junkyard
Electromagnet in a crane
→ Lifts heavy steel in a junkyard
Holds papers on the fridge door
Refrigerator magnet
→ Holds papers on the fridge door
Points toward magnetic north
Bar magnet poles
→ Named north and south ends
Named north and south ends
Each magnet application uses a different property: direction-finding, lifting, holding, or naming the ends.