What is the magnitude of the magnetic field?

1. Jun 28, 2009

mba444

What is the magnitude of the magnetic field??

1. The problem statement, all variables and given/known data

A small rectangular coil composed of 37 turns
of wire has an area of 36 cm2 and carries a
current of 0.8 A. When the plane of the coil
makes an angle of 18◦ with a uniform magnetic
field, the torque on the coil is 0.07 Nm.
What is the magnitude of the magnetic
field? Answer in units of T.

2. Relevant equations

Torque = n*i*A*B*sin(theta)
B= torque/(n*i*A*sin(theta))
n is the number of turns

3. The attempt at a solution

what i did is that i plugged all the given values .. but i keep get the wrong answer .. i dont know where is my mistake

2. Jun 28, 2009

rock.freak667

Re: What is the magnitude of the magnetic field??

Did you convert the area to m2?

3. Jun 28, 2009

jix

Re: What is the magnitude of the magnetic field??

theta is the angle made between the normal to the coil to the magnetic field. Think about it, if the coil is parallel to the magnetic field (theta = 0), the torque is maximum (the forces on the wires are directly opposite), as opposed to if you used sin 0 = 0, that is torque = 0. So you have to use sin 72 or cos 18 in the equation.

I don't even know if that's the problem, but I hope it helps.