00:01
Okay, so we're doing chapter 27, publum 15.
00:03
It says alpha particles of charge q equals plus 2e and a mass of 6 .6 times 10 to negative 27 kilograms and they're emitted from a radioactive source at a speed 1 .6 times 10 to the 7 meters per second.
00:25
Excuse me.
00:27
What magnetic field strength would be required to bend them in a circuit? circular path of radius 0 .18 meters.
00:36
So we know that the magnetic field force is perpendicular here, so we don't actually worry about the sine theta term.
00:43
So the force is given by qvb, and if we wanted to move circularly, we can set this equal to what the centripetal acceleration is, which is mv squared over r.
00:57
So now, if we're wanting to figure out what the magnetic force is, we just rearrange this and solve for what b is.
01:07
So let's rearrange this equation and you see that b equals v or mv over qr.
01:19
Well, we already have all these things so we can just plug these in...