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

  • Thread starter allok
  • Start date
16
0
hi

I recently started learning about magnetic fields and magnetic induction.
I tried to solve the following two problems, but I got stuck. Could you please help?


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. Homework Statement



2. Homework Equations



3. The Attempt at a Solution
 

Answers and Replies

Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,598
6
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
Why can't you use the formula for the inductance of a coil?
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.

Note that [itex]Li = N\phi_{B}[/itex]
 
16
0
allok said:
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
Why can't you use the formula for the inductance of a coil?
Uh, I got it now.




allok said:
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.

Note that [itex]Li = N\phi_{B}[/itex]


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


thank you
 
Last edited:

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