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### Course: Physics library>Unit 18

Lesson 5: Discovery of electromagnetism

# Right-hand rule

Learn the convention for describing the direction of magnetic fields

### Findings

As the current passes through a straight wire the magnetic field wraps around the wire in concentric circles.
If we point our thumb along the direction of current (I) flow, our fingers curl around in the direction of the magnetic field lines (B).
This means a loop of wire must create a magnetic field which flows through the loop and around the outside!

and...

## Want to join the conversation?

• How could we increase the strength of the field through a loop as shown above?
Since it is the electrical current running through the wire that creates the field, the strength of the field could be increased by having more current flow through the wire per time. Alternatively, you could increase the number of wires to increase the effect, but making sure the current goes in the same direction through all of the wires so they all "pull in the same direction" / don't cancel each other out.
• Are we supposed to answer the challenge questions in this discussion?
• How do you think the magnets react to us because we have iron in our blood?
(1 vote)
• How could we measure the force through the loop?
Use a compass. In practise, wrap the wire around the compass and observe how strongly the needle aligns with the direction of the field.
• That is how you make electromagnetisism.
• How could we increase the strength of the field through a loop as shown above?

By increasing the number of coils of wire that are wrapped around the compass.
• This flow of energy through the loop, it is considered a force? Hence the term force field? I was thinking measurement could be done w/ a voltage meter but, this energy is dispersed and not controlled through a wire. Measurement requires numbers, yes? So what instrument besides strong needle alignment would we use? Thanks for these lessons.
• Very good question. First let's stop and ask: what is a voltage meter?

(hint: you can build a volt meter using a compass & wire :-)
(1 vote)
• a coil of wire consisting of many loops called what.
(1 vote)
• what is the rest of the compass made out of?
(1 vote)
• I don't get the right hand rule
(1 vote)
• For the right-hand rule, you point your thumb in the direction of the current and curl your fingers toward your palm(👍or👎the current can be in two directions and so can the magnetic field). The direction in which you curled your fingers in, is the direction of the magnetic field(↩ or ↪).
Hope this helps!
(1 vote)
• which left hand rule and right hand rule are easy to understand
(1 vote)

Both are valid.

You need to understand the underlying assumptions. In fact, if you look closely you will see that they are the same thing.

In my opinion - stick with the right hand rule. It appears to be the most common in textbooks.

Regards,

APD
(1 vote)
• How come if you rap a wire around a compass and have a battery and connect the wire to the battery the compass spines?
(1 vote)
• It spins because of the magnetic field the wire(or current inside the wire) creates.
Since a compasses needle turns when there is something magnetic around it, the magnetic field will make it turn.
Hope this helps!
(1 vote)