00:01
So in this question we are shown a surface, hemispirical surface basically.
00:06
We are calling this surface as s1 and this curved surface that we have here.
00:15
We are calling this as s2.
00:18
Now this is the normal basically and there is a magnetic field basically whose value is b and this is exactly making an angle theta here with this axis.
00:31
This information is given to us now uh this is my normal vector and this is my b vector so what we can see from here is the angle between b vector and and n vector which is normal vector is definitely uh this angle which is 180 minus theta right so if we want to get the flux basically flux would be equal to magnetic field vector dot area vector so magnetic field vector and area vector so it would be b area a and then cause of 180 minus theta because it is the angle between the magnetic field and the area vector so flux is coming out to be magnetic field is definitely b area we are calling it as s1 and cause of 180 minus theta everybody knows cause of 180 minus theta is basically minus cost theta.
01:43
So the flux passing through surface one is coming out to be minus bs1 cost theta.
01:52
Why negative because it is entering the surface.
01:56
So that's why this sign is negative.
02:00
Now you can yourself see whatever amount of flux will pass through this upper surface as one.
02:09
The same amount of flux will come out from s2...