00:01
In this problem, you have three infinite wires, two with the currents going into the screen, the x indicating you're seeing the tail of the arrow that's indicating direction, and one with the current coming out towards you.
00:16
You're seeing the actual head of the arrow.
00:20
And we have the three currents and the separation distance between the wires as 21 centimeters.
00:28
So that will have to be converted to meters in the end.
00:33
Be 0 .21 meters.
00:37
Okay, infinite wires.
00:41
The magnetic field magnitude is given by mu -knot -i over 2 pi and see if they're infinite wires.
00:57
You know, ours is just the perpendicular distance from the wire to whatever point you're curious about or want the magnetic field at.
01:06
Now, in terms of the direct, so that's the magnitude.
01:08
In terms of the direct, in terms of the direction, let's draw some magnetic field.
01:18
So here's a current going into the screen.
01:23
Magnetic field lines are circular around it.
01:26
I didn't really do that well in terms of getting it in the center now, did i? so there's a right hand rule.
01:47
Thumb in the direction of the current.
01:50
So the thumb will be pointing into the screen.
01:52
Fingers will wrap around give you the sense of the arrows on the magnetic field line.
01:56
So the arrows would be like this.
02:01
This is a magnetic field line.
02:03
Now the magnetic field itself is you draw a tangent.
02:09
And the vector, tangent vector has the sense of the arrow.
02:17
So like here, the vector would be straight up, pointing up.
02:23
So you'd have this as your magnetic field at this point.
02:26
Likewise here, you'd have this.
02:28
Notice it's following the general sense of the arrow, matter where you draw.
02:34
It's always doing the general sense.
02:38
So that's for current going into the screen.
02:42
If you have one still circular, now thumb is out towards you, out of the screen.
03:01
Fingers are wrapping around now in a counterclockwise sense.
03:05
So you'd have these arrows on the magnetic field line.
03:10
So this is the magnetic field vector.
03:13
This is b itself at that point.
03:15
This is magnetic field line.
03:21
Don't confuse the two.
03:22
One gives you the other, but they're not the same.
03:29
So that's what we need, because depending on which current we're looking at, we're either on the right or on the left.
03:41
Okay.
03:42
So now let's look at that.
03:46
For one, you're in this picture here.
03:49
To its right, the magnetic field here would be down.
03:58
That's b1.
03:59
Two, same picture we're going to use, but now you're on the left...