The question is about F=BILsin(theta). There is a wire with a current of 4A, length 0.05m, going through a magnetic field. This is on top of a balance and gives a reading of 0.8 'gram'. It then asks us to calculate the average flux density along the length of the wire.
I went about this by saying that 0.8 grams is 0.8x10^-3 Kg. and that this represents a force of (0.8x10^-3)/9.8 N (using F=mg)
I then substitue everything into F=BIL (It's at right angles) and get '4.08 x10^-4'.
(0.8x10^-3 / 9.8) / (0.05 * 4)
Looking at the markscheme, it just says that it is 0.04T. And i can't see why i am a factor of 100 out.