Right and Left Hand Rules
You’ll find two of the most useful tools for understanding electromagnetism right at the end of your arms.
These convenient appendages help us understand the interaction between electricity and magnetism via the Right Hand Rule and the Left Hand Rule.
The Right Hand Rule, illustrated below, simply shows how a current-carrying wire generates a magnetic field. If you point your thumb in the direction of the current, as shown, and let your fingers assume a curved position, the magnetic field circling around those wires flows in the direction in which your four fingers point.
The Left Hand Rule shows what happens when charged particles (such as electrons in a current) enter a magnetic field. You need to contort your hand in an unnatural position for this rule, illustrated below. As you can see, if your index finger points in the direction of a magnetic field, and your middle finger, at a 90 degree angle to your index, points in the direction of the charged particle (as in an electrical current), then your extended thumb (forming an L with your index) points in the direction of the force exerted upon that particle. This rule is also called Fleming's Left Hand Rule, after English electronics pioneer John Ambrose Fleming, who came up with it.
Just to confuse things a little, you can also use another right hand rule to illustrate the same principles that Fleming described with his left-hand rule. Point the thumb of the right hand in the direction of the current and the rest of the fingers in the direction of the magnetic field, which extends from the north pole of a magnet to its south pole. The direction that the palm is facing when the hand is in this position is the direction of the force exerted on current (charged particles), called the Lorentz force.
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