00:01
Hello, in the question we have given that suppose a straight wire, straight 1 .85 mm diameter copper wire.
00:10
So, we have given the diameter of copper wire.
00:23
So, let us call it as d.
00:25
So, that is 1 .85 mm given.
00:29
So, the radius will be equal to half of this.
00:32
So, that is 0 .925 mm.
00:38
So, if we convert this into meters, so this radius will be 0 .925 into 10 raised to minus 3 meters.
00:48
So, this is the radius.
00:50
Now, further what they are saying this copper wire could just float horizontally in air because of the force due to the earth's magnetic field b, which is horizontal perpendicular to wire and the magnitude.
01:05
So, the magnitude of this magnetic field is given that is equal to 3 .2 into 10 raised to minus 5 tesla.
01:15
So, what current would wire carry? so, what is the current in the wire? so, now we will use over here the equation f is equals to i times b times l.
01:27
So, actually this force is equal to this i l cross b.
01:33
So, l cross b means lb sin theta.
01:36
So, the angle between they have mentioned that it is perpendicular.
01:40
So, this magnetic field is perpendicular to this wire.
01:44
So, that is why the angle is 90 degree.
01:47
So, we get this equation.
01:49
Now, one more thing that they are saying that this copper wire just float.
01:54
So, now when this copper wire will just float.
01:58
So, there should be a downward force that is the force due to gravity mg and then there should be an upward force that is the magnetic field force.
02:08
So, by using this so this should balance then only this will float this wire will float.
02:16
So, accordingly this force i can write it as mg.
02:19
So, that will be equal to ibl...