# How can you calculate change in magnetic flux?

1. Apr 3, 2005

### michaelw

Here is the problem

A long and narrow rectangular loop of wire is moving toward the bottom of the page with a speed of 0.020m/s (see the drawing). The loop is leaving a region in which a 2.4-T magnetic field exists; the magnetic field outside this region is zero. During a time of 2.0s, what is the magnitude of the change in the magnetic flux?

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2. Apr 3, 2005

### asrodan

hrm...

Since the magnetic flux is completely perpendicular to the loop, the magnetic flux at anytime is B*A, where A is only the area that is within the magnetic field.

Magnetic flux = B*A you can differentiate this equation with respect to time to find the rate of change of flux, and relate dA/dt to the information given in the question.

Because you are looking for the change only, you do not need to the know the total area, or the length, of the loop.

3. Apr 4, 2005

### michaelw

is there a way to do it without involving calculus :)?

4. Apr 4, 2005

### dextercioby

You can do it,if the velocity is constant...(I think it is).

So yes.

$$\Delta \Phi =B \Delta A$$

What is the variation of the area...?

Daniel.

5. Apr 5, 2005

### michaelw

thanks :)
are the units for magnetic flux Tm^2 (the SI unit)

6. Apr 5, 2005

### dextercioby

1 Tm^2 is equal to one 1 Weber.

Daniel.