# Magnetic field produced by a current

1. Apr 8, 2015

### carl binney

1. The problem statement, all variables and given/known data
this is the equation for flux density we have been given, the radius 30mm, z= goes in stages of 10mm, from zero to 50mm, then from zero to -50mm. that symbol at the begin of equation is 4 pie ! and the current is 5 amps. its is for a single-loop coil

2. Relevant equations

3. The attempt at a solution
I have tried the equation and the answer is nothing like my experimental results. which is 6.2 mV, at 10mm.

#### Attached Files:

• ###### IMG_1082.JPG
File size:
64.1 KB
Views:
82
Last edited: Apr 8, 2015
2. Apr 8, 2015

### Noctisdark

One of the basic formulas I've learnt is that that magnet flux density can be expressed as:
β = μ0*I*n/2πr
Where μ0 is the permeability vacu vacuum, n as the numbers of the turn of the coil and r is the distance to the coil :)

3. Apr 8, 2015

### carl binney

thanks, but i missed something out the question, the equation is for single-loop coil

4. Apr 8, 2015

### Noctisdark

Yep, that's the equation for singlz loops,
Eitherway you've got 0.003 voltage difference and unfortunately these things happens due to many errors, one of them is that we're not living in the vacuum, :)

5. Apr 8, 2015

### BvU

Hello Carl, welcome to PF !

Please read the guidelines . You get better help if you present a clear and concise problem.
What are the relevant equations ?

Apparently you are measuring something in terms of mV.
What does that have to do with the magnetic field B ?

Also your calculations should be typed (or better: typeset). But your picture does come through clearly. Pity you don't have $r^2$ in the numerator, and it's totally unclear to me why you have $30^2$ and not $(10^{-3})^2$ in the denominator. Also, the $10^2$ should be $(10\times 10^{-3})^2$

6. Apr 8, 2015

### carl binney

thanks again, I might seem stupid, I have only done physics since Christmas , I cant see how there is only a 0.003 voltage difference ???

7. Apr 8, 2015

### BvU

Oh, and $\mu_0 = 4\pi \times 10^{-7}$ N/A2, not just $4\pi$.

8. Apr 8, 2015

### carl binney

hi thanks for the advice every one, 0.01 is in the equation because the first measurement of the magnetic field was measured 10 mm away from the centre of the single loop coil, is this equation correct ?

9. Apr 8, 2015

### BvU

I get that too. Now check that you get the right units.