00:01
In this question, we're told we have a strip of silver.
00:03
It is 0 .05 millimeters thick and 20 millimeters wide.
00:11
It is in a magnetic field of 0 .8 teslers, and there are 5 .85 times 10 to the 28, 3 electrons per cubic meter.
00:20
There is a current of 10 amps through the strip.
00:23
So what we want to find first is the drift velocity of the electrons.
00:28
In order to do this, we need to use the expression.
00:31
That i, the current, is equal to a -n -e -v -d, which is the drift velocity.
00:42
E is the charge of the electron, n is the number of them present, and a is the area of the strip.
00:49
So we know all of these values, but we want to find the drift velocity.
00:54
So what we need to do is rearrange this expression to say the drift velocity is equal to the current over a -n -e.
01:04
We've been given all of these in the question.
01:07
We know that a is equal to the thickness times the width.
01:12
So we can just substitute this into here.
01:16
And what we can say is that as a result, a is equal to 1 times 10 to the minus 6 metre squared...