# Understanding Magnetic Field Hand Rules

• Mceestix
In summary, the conversation discusses using Hand rules to determine magnetic fields in relation to electric circuits. The direction of the magnetic field can be determined by curling the fingers of the right hand around the wire in the direction of the current. Placing a compass near the wire will also indicate the direction of the magnetic field. The compass needle will adjust itself to always point in the direction of the field, even if the compass is moved from above to below the wire where the field direction changes.
Mceestix
Hey everyone. Just a quick high school physics question about determining magnetic fields using Hand rules.

The only thing I have trouble trying to understand is how to determine the way a compass arrow will point if you place it on top, or under an electric circuit. I know that they are opposites of each other:yuck: :yuck: :yuck: , but i get confused trying to determine them. Any help would be appreciated.. thanks.

You mean a (more or less) straight wire, right? Curl the fingers of your right hand around the wire so that your thumb points in the direction of the current. The magnetic field runs in circles around the wire, in the direction that your fingers are curling. This is also the direction that a compass needle will point if you place it near the wire.

jtbell said:
You mean a (more or less) straight wire, right? Curl the fingers of your right hand around the wire so that your thumb points in the direction of the current. The magnetic field runs in circles around the wire, in the direction that your fingers are curling. This is also the direction that a compass needle will point if you place it near the wire.

Oh okay, that does make sense now... but what about the changes that happen to the compass if you place it on top of the wire, versus below the wire?

The compass needle will align itself with the field--as you move the compass up, down, and around the wire, the needle will adjust itself to always point in the direction of the field. So if you move the compass from above the wire to below the wire, the needle will swing 180 degrees to point in the other direction, since the magnetic field reverses direction.

## 1. What is the right-hand rule for magnetic fields?

The right-hand rule is a method used to determine the direction of a magnetic field around a current-carrying conductor. It states that if you point your thumb in the direction of the current, the direction of your curled fingers will indicate the direction of the magnetic field.

## 2. How is the left-hand rule used in relation to magnetic fields?

The left-hand rule is used to determine the direction of the force exerted on a current-carrying conductor in a magnetic field. It states that if you point your index finger in the direction of the magnetic field, your middle finger in the direction of the current, then your thumb will point in the direction of the force.

## 3. What is the difference between the right-hand rule and the left-hand rule for magnetic fields?

The right-hand rule is used to determine the direction of a magnetic field, while the left-hand rule is used to determine the direction of the force exerted on a current-carrying conductor in a magnetic field.

## 4. Can the right-hand and left-hand rules be used for all types of magnetic fields?

Yes, the right-hand and left-hand rules can be used for all types of magnetic fields, including those created by permanent magnets, electromagnets, and current-carrying conductors.

## 5. Are there any exceptions to the right-hand and left-hand rules for magnetic fields?

There are a few exceptions to the right-hand and left-hand rules, such as when dealing with magnetic fields inside a solenoid or when the current is perpendicular to the magnetic field. In these cases, different rules or equations may need to be used to determine the direction of the field or force.

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