Can't solve it - I think some data is missing for this to be solvable

1. Jan 18, 2007

allok

hi

I recently started learning about magnetic fields and magnetic induction.

1)
Current of 15 A is running through the wire loop and magnetic flux throught the wire loop is 3 Wb. What is inductivity L of a wire-loop? Here we obviously can't use formula for inductivity of a coil, so ... I don't know how to go at it.

I = 15 A
FL[ux] ... 3 Wb

2)

Current of 20 A creates inside a coil a magnetic flux of 10 Wb. What is the induced voltage U of a coil, if current decreases by 1.2 A each second? I tried to solve it but clearly there are some variables missing - like length of a coil or area of a wire-loop.

I = 20 A
FL[ux] = 10 Wb
dI = 1.2 A
dt = 1 s

U = ?

Like I said, length of a wire is missing for this to be solvable.

cheers
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 18, 2007

Hootenanny

Staff Emeritus
Why can't you use the formula for the inductance of a coil?

Note that $Li = N\phi_{B}$

3. Jan 18, 2007

allok

Uh, I got it now.

I got it now. I didn't notice that problem already stated how many turns coil has.

thank you

Last edited: Jan 18, 2007