# Compass Between two wires

• Samurai44
In summary, two parallel wires with the same magnitude of current flow and a distance of 10cm between them will create circular magnetic fields around each wire, with wire A's field being counterclockwise and wire B's field being clockwise. The direction of the needle in a compass placed at 4cm from wire A will depend on the superposition of the magnetic fields from both wires. If the compass is at a midpoint between the two wires, the fields will cancel out and the needle will not point in a specific direction. Otherwise, the needle will point in the direction determined by the sum of the magnetic fields at that location.

## Homework Statement

two wires are parallel to each other,carries current of same magnitude, and the distance between them is 10cm ,, wire A carries current out of the page ,, Wire B carries current into the page ... A compass is placed at 4 cm from wire A .. Where does the needle point ?

I also would like to know where does the needle will point if the two wires carries same current direction

## Homework Equations

-
same current direction - Attraction
opposite current direction - Repulsion

## The Attempt at a Solution

I drew the magnetic field around each wire(Wire A-Anticlockwise ... Wire B-Clock wise) , but since the field is circular around a straight wire , so I couldn't know where it will point exactly .

Samurai44 said:
I drew the magnetic field around each wire(Wire A-Anticlockwise ... Wire B-Clock wise) , but since the field is circular around a straight wire , so I couldn't know where it will point exactly .
It will be tangent to the circle at any location around the circle.

gneill said:
It will be tangent to the circle at any location around the circle.
so the other wire won't affect the direction of the needle unless the compass was at mid point ?

Samurai44 said:
so the other wire won't affect the direction of the needle unless the compass was at mid point ?
No, the fields from both wires will sum at any given location (superposition principle). Pick a location and sketch the circles centered on each wire that pass though that point. Sketch in the field vector at that point for each wire. Sum the vectors.

gneill said:
No, the fields from both wires will sum at any given location (superposition principle). Pick a location and sketch the circles centered on each wire that pass though that point. Sketch in the field vector at that point for each wire. Sum the vectors.
alright thanks