# Homework Help: Question about Magnetic induction of circular loop

1. Mar 12, 2017

### BREAD

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

2. Relevant equations

3. The attempt at a solution

This is what i did about (a)
but i don't know how to approach (b), it doesn't have x,y components, only Bz component.

2. Mar 13, 2017

### haruspex

I think your answer to a is right - not expert in this area.
For b, a dependent variable being zero at some value of the independent variable does not imply that its derivative is also zero there.
I suggest working on b2, returning to b1 afterwards.

3. Mar 13, 2017

### BREAD

I think i solve (1), but the problem is (2),(3)

4. Mar 13, 2017

### haruspex

And very neatly too.
These are easy. Fundamental differential calculus: f(x+Δx)≈f(x)+f'(x)Δx.

5. Mar 13, 2017

### BREAD

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I tried it , but is (2) right? and idw how to get ∂(B_z)/∂y|_(0, 0, z). I heard somewhere that by properties of curl of B (as i wrote)
∂(B_z)/∂y|_(0, 0, z) is changed to ∂(B_y)/∂z|_(0, 0, z), but i can't solve this.

6. Mar 13, 2017

### haruspex

Isn't By identically zero on the z axis?

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