Why Is It Sin Theta Instead of Cos Theta in Magnetic Flux Calculation?

In summary, the homework statement is trying to find the angle between the plane of a coil and the magnetic field. However, the angle shown in the diagram does not subtend the area normal and the magnetic field direction.
  • #1
watthappening
5
0

Homework Statement


I had know that for finding magnetic flux is NBA cos theta. The answer is C though, so why is it sin theta instead of cos theta? I wonder
18579155_1673876892626038_1946895226_n.jpg

Homework Equations


BA cos theta
NBA cos theta[/B]

The Attempt at a Solution

 
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  • #2
This is the problem with memorizing formulas without making sure you know what the variables represent. Try to find in your notes or textbook where that formula was defined and see how the angle θ is defined there.
 
  • #3
gneill said:
This is the problem with memorizing formulas without making sure you know what the variables represent. Try to find in your notes or textbook where that formula was defined and see how the angle θ is defined there.
I did know what the variables represent, the angle is between the normal of the area of the surface and magnetic field lines. But i still didnt get the reason.
 
  • #4
watthappening said:
I did know what the variables represent, the angle is between the normal of the area of the surface and magnetic field lines. But i still didnt get the reason.
Okay, the angle in the given diagram does not subtend the area normal and the magnetic field direction. How does this given angle relate to the angle used in the definition? (It may help to use a little triangle geometry)
 
  • #5
gneill said:
Okay, the angle in the given diagram does not subtend the area normal and the magnetic field direction. How does this given angle relate to the angle used in the definition? (It may help to use a little triangle geometry)
It's doesnt? oh well, I didnt know that
 
  • #6
watthappening said:
It's doesnt? oh well, I didnt know that
The required area normal is perpendicular to the area of the coil "face", that is, it's perpendicular to the plane of the coil. The angle shown in the diagram subtends the magnetic field and the plane of the coil itself.
 
  • #7
gneill said:
The required area normal is perpendicular to the area of the coil "face", that is, it's perpendicular to the plane of the coil. The angle shown in the diagram subtends the magnetic field and the plane of the coil itself.
is this correct?
18579420_1674036752610052_1806037394_n.jpg
 
  • #8
Sure. That'll work. You should be able to see the relationship between the θ given in the problem figure to the one you've just drawn in.
 
  • #9
gneill said:
Sure. That'll work. You should be able to see the relationship between the θ given in the problem figure to the one you've just drawn in.
alright thanks for the help, mate
 

FAQ: Why Is It Sin Theta Instead of Cos Theta in Magnetic Flux Calculation?

What is the angle for magnetic flux?

The angle for magnetic flux is the angle between the magnetic field lines and a surface or object. It is measured in degrees or radians.

How is the angle for magnetic flux calculated?

The angle for magnetic flux is typically calculated using trigonometry, specifically the cosine function. The formula is cos(θ) = B⃗ · A⃗ / (|B⃗| |A⃗|), where B⃗ is the magnetic field vector and A⃗ is the surface or object vector.

Why is the angle for magnetic flux important?

The angle for magnetic flux is important because it determines the strength of the magnetic field acting on a surface or object. A larger angle means a weaker magnetic field, while a smaller angle means a stronger magnetic field.

How does the angle for magnetic flux affect the amount of induced current?

The angle for magnetic flux is directly proportional to the amount of induced current. This means that the larger the angle, the less current will be induced, and vice versa. This is known as Faraday's law of induction.

Can the angle for magnetic flux be changed?

Yes, the angle for magnetic flux can be changed by rotating the surface or object with respect to the magnetic field. This can also be achieved by changing the direction or strength of the magnetic field itself.

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