Magnetic Fields

Science · Forces & Motion · ages 11-12

Name ______________________ Date ____________

Ana wants to draw the field pattern around a bar magnet. Which tool does she move around the magnet, marking which way it points at each spot?
- A small compass
- A wooden ruler
- A steel spring
A compass needle points north because sunlight warms it.
Circle one: True False
Mia opens a compass and finds a small needle balanced so it can turn easily. When she holds a magnet nearby, the needle swings toward it. Why does the needle react to the magnet?
- The needle is warmed by her hand
- The needle is a tiny magnet itself, so it feels the field
- The needle is pulled down by gravity
What shape are the magnetic field lines around a straight wire carrying current?
- Circular lines around the wire
- Straight lines along the wire
- No field at all
- Lines going into the wire
Ravi takes 3 compass readings near the north pole of a magnet, 3 near the south pole, and 4 along the sides. How many readings does he take in all?
Answer: ______________
Ravi holds a field sensor 2 cm from a magnet's pole and reads 10 units. He moves it to 6 cm away and reads 4 units. How many units did the reading drop?
Answer: ______________
On a boat far out at sea, with no land or magnets anywhere near, a compass still settles pointing north. What is the needle lining up with?
- The Earth's magnetic field, which reaches the boat too
- The pull of the nearest land
- The boat's engine
At 4 cm from a magnet, Mia's field sensor reads 8 units. She moves the sensor to 2 cm, twice as close, and the reading doubles. What does the sensor read now?
Answer: ______________
Omar says a compass would still point in a fixed direction even if the Earth had no magnetic field. Is he right?
- No, the needle would have nothing to line up with, so it could settle pointing any way
- Yes, gravity would still make it point north
- Yes, it would point toward the sun instead
A compass sits far from any magnet and points north. Zara brings a strong bar magnet right up next to it. What does the needle do?
- It keeps pointing north, because compasses can only point north
- It swings to line up with the bar magnet's field right beside it
- It stops moving and sticks in place

Answer key

For grown-ups. Fold this page away before handing over the rest.

Magnetic Fields W1-mt_56aspHjU19-s1

A small compass · A small compass lines up with the field at each spot, so moving it around the magnet reveals the field pattern.
False · A compass needle points north because it lines up with the Earth's magnetic field, not because of sunlight.
The needle is a tiny magnet itself, so it feels the field · Only a magnet feels a magnetic field. The needle reacts because it is a tiny magnet that can swing freely.
Circular lines around the wire · Electric current in a wire creates a magnetic field with circular field lines around the wire. The direction follows the right-hand rule.
10 · Three groups of readings, 3 and 3 and 4, add up to 10 readings in all.
6 · The reading fell from 10 units to 4 units, and 10 take away 4 is 6, so it dropped by 6 units.
The Earth's magnetic field, which reaches the boat too · The Earth acts like a giant magnet, so its field reaches even a boat far out at sea, and the needle lines up with it.
16 · Moving closer means a stronger field, and doubling 8 units gives 16 units.
No, the needle would have nothing to line up with, so it could settle pointing any way · A compass needle only points north because it lines up with Earth's magnetic field. Without that field, it would have nothing to align with.
It swings to line up with the bar magnet's field right beside it · A compass needle lines up with the field around it. A strong magnet right beside it is what the needle feels most, so it swings to line up with the bar magnet's field.