The field around a wire and a solenoid, the right-hand grip rule, what makes an electromagnet stronger, and where electromagnets are used.
What you will learn
- Describe the field around a straight wire and a solenoid
- Use the right-hand grip rule for the direction of a field
- Explain how to make an electromagnet stronger and how a relay works
A current makes a field
A wire carrying a current has a magnetic field round it.
For a long straight wire the field lines are circles centred on the wire.
- A bigger current gives a stronger field.
- The field gets weaker further from the wire.
- Reverse the current and the field reverses.
Right-hand grip rule: grip the wire with your right hand, thumb pointing along the current. Your fingers curl the way the field lines go. If the current comes towards you (out of the page), the circles go anticlockwise; if it goes away from you, clockwise.
The rest of this lesson and its 9 practice questions are locked.
In this lesson
- A current makes a field
- Coil it up: the solenoid
- Electromagnets
- Try it: The field of a current
9 practice questions, marked as you go; about 20 minutes in all.
Key terms
Solenoid, Iron core
In this unit: Magnetism and electromagnetism
Magnets and field lines, electromagnets, the motor effect and F = BIl, then loudspeakers, generators, microphones and transformers.