A push you cannot touch
The space around a magnet where its pull can be felt.
Needle that turns
A compass needle is a tiny magnet. It turns when a magnet is brought near it, even through things that are not magnetic.
What do you think can make a compass needle turn?
What this lesson covers
The idea
The region around a magnet or a current-carrying wire where its magnetic effect can be felt, such as by the deflection of a compass needle, is said to have a magnetic field.
Needle that turns
A compass needle is a tiny magnet. It turns when a magnet is brought near it, even through things that are not magnetic.
What do you think can make a compass needle turn?
- A magnet brought near it
- Only a push from a finger
- Only the wind
Switch it ON and OFF
Switch the current ON, then OFF. Watch the needle and the glowing region around the wire.
The needle felt something
The needle turned only when the current flowed. So the wire had a magnetic effect on it. The region where this effect can be felt is the magnetic field.
The region around a magnet or a current carrying wire where its magnetic effect can be felt, such as by the deflection of a compass needle, is said to have a magnetic field.
Notes
The region around a magnet or a current carrying wire where its magnetic effect can be felt is said to have a magnetic field.
Check yourself
The region around a magnet where its magnetic effect can be felt is its …
Which of these shows that a compass needle is inside a magnetic field?
A compass needle near a wire carrying current deflects. This shows that the wire has …
Which of these has a magnetic field around it?
- electric circuit. A circuit is a path for current. It is not the region of a magnetic effect.
- magnetic field — correct. Yes!
- compass. A compass only shows the field. It is not the field.
- The needle gets longer. A change in length tells us nothing about a magnetic effect.
- The needle gets warm. Warmth is not how we detect a magnetic field. A deflection is.
- The needle deflects — correct. Yes!
- a magnetic effect — correct. Yes!
- no effect. The needle moved, so the wire has an effect on it.
- a heating effect. A deflected needle shows a magnetic effect. It does not show heat.
- A wire with no current in it. When the current stops, the magnetic effect disappears.
- A wire carrying current — correct. Yes!
- A lamp that is switched off. Nothing is flowing through it, so there is no magnetic effect.