In the figure below, a long straight wire carries a current of 8.5 Amps.(adsbygoogle = window.adsbygoogle || []).push({});

(Attached)

Find the magnitude of the net force (in N) on a rigid square loop of wire of side, L, equal to 5.35 cm. The center of the loop is d = 10.40 cm from the wire and the loop carries a current of 10.0 Amperes.

I don't really know where to start on this one. I realize that the segments perpendicular to the length of wire with current I1 can be discarded as not contributing any force right? I don't know where to proceed from there. Your help is greatly appreciated.

Well I sort of figured out how to do it but I think I'm screwing the sign up somewhere:

[tex]F = iL \cross B[/tex]

[tex]B = \frac{\mu I_1}{2 \pi r}[/tex]

And sum up the force on the top and bottom of the square from the long wire? Do I add the force being exerted on the top of the loop from the bottom of the loop and vice versa?

Edit: Here is my work (let subscript t be top and b be bottom)

[tex]F = \frac {u_0I_1I_t L_t}{2 \pi r_t} + \frac {u_0I_1I_bL_b}{2 \pi r_b}[/tex]

[tex]F = \frac {2 \times 10^{-7} \times 8.5 \times -10 \times 0.0535}{0.07725} + \frac {2 \times 10^{-7} \times 8.5 \times 10 \times 0.0535}{0.13075}

= about 9 \times 10^-6N[/tex]

which is wrong

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Magnetc force from current-carrying wires - help

**Physics Forums | Science Articles, Homework Help, Discussion**