Everything Waves: Sound


Power in physics

Centripetal acceleration

Series circuits


Left hand rules

Properties of magnets and motors


Newton's Law of Gravitation

Strong Nuclear Force

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In our exploration of magnetic fields and the left hand rules, keep in mind that the right-hand rules in the textbook only apply to conventional (positive) current. In many cases, electricity often has non-conventional (non-positive) current. Non-conventional current follows the left-hand rules. In this explanation, we will only use the three left-hand rules. Additionally the following definitions will be helpful in understanding how and why the left hand rules work


A permanent magnet has two poles, a north-seeking pole and a south-seeking pole. A north pole is attracted to a south pole of any magnet and repels the north pole of any magnet. The same applies for the South Pole. The north pole of any magnet will always align itself to the ch like a compass) if suspended by a thread and left alone.


A solenoid is a fancy word for a long string of wire wrapped around another cylinder object. When conventional current flows through the wire as shown, the magnetic field is unifom through the center cylinder. The following is an image of the solenoid (the blue lines are the magnetic field lines) The diagram shows that the interior of the solenoid will exhibit a North magnetic pole on the left hand side of the diagram



Applies only to third left hand rule:

$ F = IL|\vec{B}| $


  • $ F $ = Force (N)
  • $ I $ = Current (A)
  • $ B $ = Tesla (N / (A x m))
  • $ L $ = Length of wire (m)

The New VectorsEdit

One of the most confusing parts about magnetic fields is that, unlike electric fields, magnetic fields require three-dimensional analysis because the field circles around a current in a wire. Up, down, left and right no longer suffice in describing the direction of the field. Now the magnetic fields can travel into the page and it could travel out of the page.

Left Hand Rule #1Edit

The graphic & rule as describe below are incorect - This should actually be Ampere's Right hand grip rule (also known as the corkscrew rule), same principle, but right hand not left...

Pretend you are wrapping your fingers around a thin rod (in other words, make a fist) and point your thumb in the direction of the current (I). The magnetic field will circle around your fist like in the following diagram. Additionally, the magnetic field will always point in the direction your fingers are curled. Use the following diagram for reference to both the new vectors and the first left hand rule.


Left Hand Rule #2Edit

Wrap your fingers around the solenoid so that your fingers are traveling the same direction as the current (I). Extend your thumb along the cylinder object. As long as the current continues to flow in the direction your fingers are curled, your thumb will always point toward the north pole. Look at the above diagram to get a sense of it, except the rod would be a solenoid and the direction the thumb is pointing is to the north pole.

Left Hand Rule #3Edit

This rule is used to describe a force when current or electrons are run through a magnetic field. To find the magnitude of the force, just use F = BIL. To find the direction, you open your palm and make your thumb perpendicular to your fingers. Your thumb represents the direction of the current or the velocity of the electric charge (I). Your other four fingers represent the direction of the magnetic field (B). Finally, The direction of your palm is facing is the direction of the force vector. Remember, when you apply these rules, you have six basic vectors to work with (up, down, left, right, into, out of).