# Please help me with magnetic fields - how can i find its direction?

• michaelw
In summary, the net magnetic field at point P, where two wires with a current of 85.0 A are oriented perpendicular to the plane of the paper, is found by using the Right Hand Rule #2 to determine the direction of each wire's magnetic field at that point. The direction of B1 is 30.0° below the horizontal to the right, while the direction of B2 is 30.0° below the horizontal to the left. This is because the RHR only applies to the specific point being analyzed, and the wires are not parallel to each other at that point. The angle of 30 degrees is calculated by considering the equilateral triangle formed by the slanted sides of the wires and the line from each
michaelw
Please help me with magnetic fields - how can i find its direction??

The drawing shows two wires that carry the same current of I=85.0 A and are oriented perpendicular to the plane of the paper. The current in one wire is directed out of the paper, while the current in the other is directed into the paper. Find the magnitude and direction of the net magnetic field at point P.

according to the answer,
"The direction of B1 is 30.0° below the horizontal to the right. The direction of B2 is 30.0° below the horizontal to the left."

but why? if you use the RHR#2 (thumb into page for the one on the right, fingers curl in direction of magnetic field), isn't the magnetic field circular all around it? why is it in one direction?

whoops here's the pic

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michaelw said:
The drawing shows two wires that carry the same current of I=85.0 A and are oriented perpendicular to the plane of the paper. The current in one wire is directed out of the paper, while the current in the other is directed into the paper. Find the magnitude and direction of the net magnetic field at point P.

according to the answer,
"The direction of B1 is 30.0° below the horizontal to the right. The direction of B2 is 30.0° below the horizontal to the left."

but why? if you use the RHR#2 (thumb into page for the one on the right, fingers curl in direction of magnetic field), isn't the magnetic field circular all around it? why is it in one direction?

The answer given is talking about the fields AT POINT P and nowhere else. You have the RHR OK, but remember it applies to each individual point surrounding the wire.

thanks
but that doesn't add up..
why is it just the field 30 degrees below the horizontal considered?

hoops nm i think iget it

thanks =)
one more quick question
how can u calculate that angle? (30degrees)

michaelw said:
thanks =)
one more quick question
how can u calculate that angle? (30degrees)

It is an equilateral triangle. The slanted sides make an angle of 60 degrees with the horizontal. B is perpendicular to the line from each wire to P.

Last edited:
gotcha
thanks

## 1. What is a magnetic field?

A magnetic field is an area surrounding a magnet or a moving electric charge that exerts a force on other magnets or moving charges. It is represented by lines of force that indicate the direction and strength of the magnetic field.

## 2. How can I find the direction of a magnetic field?

The direction of a magnetic field can be determined using a compass. The needle of a compass will align itself along the lines of force in the magnetic field, pointing towards the magnetic north pole. The direction of the magnetic field is always perpendicular to the direction of the compass needle.

## 3. What factors affect the direction of a magnetic field?

The direction of a magnetic field is influenced by the direction of the electric current flowing through a wire, the direction of the magnetic poles of a magnet, and the distance between the magnet and the point where the magnetic field is being measured.

## 4. How can I use the right hand rule to determine the direction of a magnetic field?

The right hand rule is a method used to determine the direction of a magnetic field around a current-carrying wire. If you point your right thumb in the direction of the current and curl your fingers, the direction in which your fingers curl is the direction of the magnetic field.

## 5. Can the direction of a magnetic field be changed?

Yes, the direction of a magnetic field can be changed by changing the direction of the electric current, reversing the poles of a magnet, or altering the distance between the magnet and the point where the magnetic field is being measured.

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