# Question on Magnetic Fields

1. May 17, 2005

### lightuplightup

I dont understand this question at all- could someone please help- at least giving me a starting point- thanks

A wire, of length 70cm is placed into a magnetic field of strength 0.001T. If the wire carries a current of 5 amps
1/ Calculate the magnitude of the forces on the wire if it is successively oriented at 900, 550, 350 and parallel to the magnetic field
2/ Draw a graph showing the variation of the force as the angle changes
3/ What will be the shape of the graph if the force is plotted against sin0
4/ Draw a graph of force against sin0

I know for the first one you have to use F=BILsin0 but i dont understand the co-ordinates- what angle am i supposed to use- What does 900, 550 and 350 mean???? I think if i get this first bit understood then i will be able to complete the other parts.

Thanks

2. May 17, 2005

### roger

Look, you know that the magnitude of force is maximum and minimum when the angle between the field and current carrying wire is perpendicular and parallel respectively.(when BIL is constant).
So simply put in the values you are given into your formula and there we are.
I'm sure they are meant to be in degrees, and the angle theta is between the magnetic field and wire.

3. May 17, 2005

### James R

In the formula:

$$F=BIL\sin \theta$$

the angle is the smallest angle between the magnetic field vectors (or field lines) and the wire carrying the current.