0:00
All right, hello.
00:01
In the first part of this question, we're told that we have a piece of metal, a bar, moving through a magnetic field, which is directed into the page.
00:09
And it experiences a charge separation where all the negative charges go to the left and all the positive charges go to the right.
00:17
We're asked, which way is this moving? well, in order to answer this, we're going to have our equation for our magnetic force.
00:23
So we know that our magnetic force is going to be q times v crossed with b.
00:28
And this v is going to be the direction that the charges are moving.
00:32
So in our bar here, we know that we have a positive magnetic force acting on positively charged particles.
00:40
So what that means is for my, quote unquote, positive charge carriers, i'm going to have a force that pushes them to the right.
00:50
So i'm going to have some magnetic force.
00:52
And that is going to be a positive force going to the right.
00:56
I know what direction b is.
00:58
I know it's into the page.
00:59
So i can go ahead and figure out what v is going to be by taking my right hand.
01:03
And i extend my fingers out.
01:05
I have my thumb out at a 90 -degree angle.
01:07
I know that i want my fingers to point in the direction of b.
01:10
So they're going to be going into the page.
01:12
And then i'm going to want my palm to point in the direction of the force.
01:15
So i'm going to have my fingers into the page.
01:17
My palm is facing to the right.
01:19
And if i do that, my thumb is going to be facing down.
01:22
So that must be the direction that i have my velocity.
01:27
So it's going to be down or towards the bottom of the page.
01:30
So that's going to be d in this case.
01:33
We're told for the second part of this question that we have a bar magnet here with its north end approaching a loop, which is going to have a current induced in the clockwise direction.
01:43
So this loop must be, or this bar magnet must be moving to the right with some speed v.
01:48
And we're asked in this situation, what condition is met such that the loop has its greatest magnitude for current and that current is in the clockwise direction? so i know this bar is traveling to the right because i'm told that just as the north pole enters the loop is an option and as the south pole leaves the loop.
02:08
So i know that that's how i know it's traveling to the right.
02:11
Let's go ahead and look at a few of these different scenarios.
02:16
So first off, i can immediately discredit a and e because if my bar magnet is further away from the loop, i'm going to have less magnetic flux.
02:24
And therefore, my induced current is going to be less because i know that my induced voltage, which leads to my induced current, is the opposite of my change in flux over my change in time.
02:34
And i know that my change in flux, my flux is going to be b times a here.
02:40
The area is constant, so i really just want to talk about how b is changing.
02:44
So i'm going to go ahead and draw our bar magnet here, looking, this is kind of just a side -on view...