In one of the previous Physics exam papers that I've got, there's a question which has a diagram of a negatively charged cloud, above a positively charged ground. There's a line from the cloud down to the ground, which signifies a lighting strike.
There is a point P slightly to the right of the lightning strike. I'm asked to state the direction that the magnetic field due only to the lightning strike is..
I'm guessing that I'd simply use flemings left-hand rule...
I know the direction of the current (cloud to ground); but I also need to know the direction of the force.
But, it doesn't seem to give this information...
The correct answer for the direction of the magnetic field at point P is 'in to the page'. But where have they deduced the direction of the force/motion ?