What Is the Magnetic Field at the Midpoint Between Wires M and N?

[Queue]

Homework Statement

Three long parallel wires are 4.0 cm from one another. (Looking along them, they are at three corners of an equilateral triangle.) The current in each wire is 8.00 A, but its direction in wire M is opposite to that in wires N and P. By convention we can say that M is at the top of our equilateral triangle and N on the lower left hand corner.

Determine the magnitude and direction of the magnetic field at the midpoint of the side of the triangle between wire M and wire N.

Homework Equations

B = [tex] \frac{\mu_0 I}{2 \pi r}[/tex]

The Attempt at a Solution

I was put these answers into mastering physics and I got the angle wrong. I have tried tan(P/2M) and tan(2M/P) where M and P are the magnetic fields from M and P respectively.

Am I doing something wrong? Its given units are 'degrees below horizontal' and I have no idea what, exactly, is meant by the horizontal. Many thanks for any input!

 

[lanedance]

Hi Queue

I think you are determining the angle of a triangle formed by the perpindicular components (ie from M&N vs P components). These are perpindicular & parrallel to the triangle side MN respectively.

This is the first step, however the question asks the angle form a horizontal line. What is the angle between MN side & the horizontal? (what are the angles of an equilateral triangle?)

drawing a picture is usually always a good idea if you haven't already - cheers

 

[nlightner]

I would first check my calculations and make sure I am using the correct equations and units. I would also double check the given information and make sure I understand the setup of the problem correctly.

In this case, the magnetic field at the midpoint of the side between wire M and N can be calculated by using the equation B = \frac{\mu_0 I}{2 \pi r}, where I is the current in each wire and r is the distance from the midpoint to the wires. Since the wires are parallel, the magnetic field from each wire will be in the same direction and can be added using vector addition.

To determine the direction of the magnetic field, I would use the right hand rule, where I point my thumb in the direction of the current and my fingers curl in the direction of the magnetic field. I would also make sure to use the convention that the current in wire M is opposite to the direction in wires N and P.

If you are still having trouble getting the correct angle, I would suggest checking with your instructor or a classmate for help. It is also important to understand the concept and reasoning behind the solution, rather than just getting the right answer.