Electromagnetism, finding magnetic field strength

[physics604]

1. A 0.034 kg copper rod is hung by two wires and placed in a constant magnetic field. A current
of 14 A runs through the 0.050 m long copper rod, making it hang at an angle of 34° from the vertical as attached in the diagram.

What is the magnetic field strength holding the copper rod in this position?

A. 27×10^-1 T
B. 32×10^-1 T
C. 39×10^-1 T
D. 48×10^-1 T

Homework Equations

$\phi$=B×Acosa
F=IlB

The Attempt at a Solution

The thing is, I don't really know where to start.

I know that the rod is at 34° (not perpendicular), so I know the formula $\phi$=B×Acosa has to be involved somehow. However, I'd only be solving for $\phi$ and I don't know the area so that really isn't very helpful.

I'm also given I and l to find B, and the only equation that looks has these variables is F=IlB. But that would me I need to find force and the other equation is F=QvB and we don't have many variables in that one.

 

[Simon Bridge]

Start by drawing a free body diagram.

 

[physics604]

Okay, I think I got it. So I would solve for the force of tension in the wires and that would be the F. Then I would do B=F/Il.

Just one more question: when I finish solving for F_T, would I have to double it to find F (since there are two wires)?

 

[Simon Bridge]

It's basically a pendulum (use the side view).
If the tension in each wire is T, then the total tension is 2T.
Did you remember the magnetic force and gravity?

 

[Nickie]

I would first start by understanding the physical setup described in the problem. A copper rod hanging at an angle of 34° from the vertical suggests that it is experiencing a force due to a magnetic field, causing it to hang at an angle instead of being perpendicular.

Next, I would use the equation F=IlB to solve for the magnetic field strength (B). We are given the current (I) and the length of the rod (l), so we just need to find the force (F) acting on the rod.

To find the force, we can use the equation F=mg, where m is the mass of the rod and g is the acceleration due to gravity (9.8 m/s^2). We are given the mass of the rod (0.034 kg), so we can calculate the force (F=0.034 kg x 9.8 m/s^2 = 0.3332 N).

Now, we can plug in our values into the equation F=IlB and solve for B. B=F/Il = 0.3332 N / (14 A x 0.050 m) = 0.476 T.

Therefore, the correct answer is D. 48×10-1 T.