If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

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).
righthand
This means a loop of wire must create a magnetic field which flows through the loop and around the outside!
loop

Challenge: Amplify & Measure

How could we increase the strength of the field through a loop as shown above?

and...

How could we measure the force through the loop?

Want to join the conversation?

  • male robot hal style avatar for user Håvard Geithus
    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.
    (20 votes)
    Default Khan Academy avatar avatar for user
  • male robot hal style avatar for user Håvard Geithus
    Are we supposed to answer the challenge questions in this discussion?
    (7 votes)
    Default Khan Academy avatar avatar for user
  • male robot hal style avatar for user Håvard Geithus
    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.
    (8 votes)
    Default Khan Academy avatar avatar for user
  • duskpin ultimate style avatar for user Erica Eng
    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.
    (5 votes)
    Default Khan Academy avatar avatar for user
  • aqualine seed style avatar for user R Black Feather
    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.
    (3 votes)
    Default Khan Academy avatar avatar for user
  • piceratops seed style avatar for user Aneeb Iqbal
    a coil of wire consisting of many loops called what.
    (1 vote)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user Zack Amyx
    what is the rest of the compass made out of?
    (1 vote)
    Default Khan Academy avatar avatar for user
  • purple pi purple style avatar for user sanghoon choi
    I don't get the right hand rule
    (1 vote)
    Default Khan Academy avatar avatar for user
    • starky sapling style avatar for user ₦Ɇ฿ɄⱠ₳
      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)
  • piceratops sapling style avatar for user arlagadda jeevan
    which left hand rule and right hand rule are easy to understand
    (1 vote)
    Default Khan Academy avatar avatar for user
    • purple pi purple style avatar for user APDahlen
      Hello Arlagadda,

      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)
  • male robot hal style avatar for user William Kilpatrick
    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)
    Default Khan Academy avatar avatar for user