Hi Dr Dusk,
I just meant a coil that has the shape of a circle instead of a rectangle (like the one in the video).
At around 7:10 min, he mentioned that the equation τ = nBIAsin(θ) applies to any area, 'A', (not just rectangular coils), so I was just wondering why that was the case.
Thanks!
We technically approximate that as a rectangle. The one in the video is considered a 'rectangle' and for all intents and purposes for the HSC it's a rectangle.
Think about it like this. Torque is just multiplying force by distance right. So if you take a rectangle for example you look at the two sides of the rectangle which have torque and multiply their force by the distance from the axis of rotation. Now the force acting on one of the sides is given by
Now if we look at the equation '2d' and 'L' multiplied together actually equals the
AREA which gives us the formula in the video. Now if we consider a circle instead of a rectangle, what do we determine as a side? As in what do you define by one 'side' of a circle? It's fully curved everywhere. So we cannot say that the force is given by BILsin(theta) which means the torque on a circular coil is
NOT the same as the formula given in the video NBIAsin(theta). So the answer is
no we cannot use that formula for a circular coil.
Mod Edit: Merged consecutive posts