Magnet Flux + Fields Problem - Please help

In summary, the conversation focused on a coil with a radius of 4cm placed in a uniform magnetic field of 2mT. The field was switched off in 1ms, resulting in a momentary current of 4mA. The questions asked were about the change in magnetic flux and the rate of change of flux during this time. The answer for the change in flux was calculated to be 0.01 Wb, while the rate of change of flux is determined by dividing the change in flux by the change in time.
  • #1
TheKovac
24
0

Homework Statement


A coil of radious 4cm has its plane perpendictular to a uniform magnetic field of strenght 2 mT directed into the page as in the following diagram

http://i83.photobucket.com/albums/j283/cowsgomoo47/physics_prob_magnetism.jpg [Broken]

The magnetic field is then switched off is such a way that it takes 1ms to drop to zero. When switched on again it also takes 1 ms. Switching off the field results in a momentary current of 4ma flowing through the milliameter from X to Y.

a) What is the change in magnetic flux through the coil when the field is turned off?

b) What is the rate of change of flux through the coil during this time?

Homework Equations





The Attempt at a Solution


a) [tex]\Phi[/tex]=BA
=> ((3.14)x(4*10^-3))^2 x (2x10^-3)


b) I = [tex]\frac{change in magnetic flux}{change in time}[/tex]
=> (4x10^-3) = (change in magnetic flux)/ (1x10^-3)
=4x10^-6
X WRONG
Right = 0.01 Wb <-- How??
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
The rate of change of magnetic flux doesn't give you the current. It gives you the induced emf.

You have found [tex]\triangle \Phi_B[/tex]. You know what is [tex]\triangle t[/tex]. See how to find the rate of change of flux?
 
  • #3





Firstly, it is important to note that the given diagram is not visible, so it is difficult to fully understand the problem. However, based on the given information, here is a response to the questions asked:

a) The change in magnetic flux through the coil can be calculated using the equation \Delta\Phi = \int \vec{B} \cdot d\vec{A} where \vec{B} is the magnetic field and d\vec{A} is the differential area. In this case, since the magnetic field is uniform and perpendicular to the coil, the angle between \vec{B} and d\vec{A} is 0 and the integral simplifies to \Delta\Phi = B\Delta A. The change in area can be calculated as \Delta A = \pi r^2 = \pi (0.04)^2 = 0.005 m^2. Therefore, the change in magnetic flux is \Delta\Phi = (2 \times 10^{-3} T)(0.005 m^2) = 1 \times 10^{-5} Wb.

b) The rate of change of flux can be calculated using the equation \frac{d\Phi}{dt} = \frac{\Delta\Phi}{\Delta t}. Since the time taken for the magnetic field to drop to zero is 1 ms, or 0.001 s, the rate of change of flux is \frac{1 \times 10^{-5} Wb}{0.001 s} = 10 Wb/s. This is the same as saying the magnetic flux is changing by 10 Wb every second.

It is important to note that the given problem does not specify the direction of the magnetic field or the coil, so the signs of the values calculated may be different depending on the direction of the field and coil. Additionally, the given problem does not specify the units of the values calculated, so it is important to double check that the units are consistent throughout the calculations.
 

What is magnet flux?

Magnet flux is a measure of the amount of magnetic field passing through a given area. It is represented by the symbol Φ and is measured in units of weber (Wb).

What are magnetic fields?

Magnetic fields are regions of space where magnetic forces can be detected. They are created by moving electric charges and can be represented by lines of force that show the direction and strength of the magnetic field.

What is the relationship between magnet flux and magnetic fields?

Magnet flux is directly proportional to the strength of the magnetic field and the area through which it passes. This means that an increase in either the strength of the magnetic field or the area will result in an increase in magnet flux.

How can I calculate magnet flux?

Magnet flux can be calculated using the equation Φ = B x A, where B is the magnetic field strength and A is the area through which the magnetic field passes.

What are some real-world applications of magnet flux and magnetic fields?

Magnet flux and magnetic fields have many practical applications, such as in electric motors, generators, MRI machines, and compasses. They are also used in industries such as electronics, transportation, and energy production.

Similar threads

  • Introductory Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
768
  • Introductory Physics Homework Help
Replies
2
Views
961
  • Introductory Physics Homework Help
Replies
31
Views
4K
  • Introductory Physics Homework Help
Replies
14
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
8K
  • Introductory Physics Homework Help
Replies
29
Views
2K
Replies
10
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
Back
Top