# Homework Help: Which of these possibilities will produce emf

1. Oct 12, 2009

### songoku

1. The problem statement, all variables and given/known data
Which one will produce e.m.f?
(i) A circular coil placed in a non-homogenous magnetic field
(ii) A circular coil moved with constant velocity in a homogenous magnetic field
(iii) A circular coil moved with constant velocity in a non-homogenous magnetic field
(iv) None of the above

2. Relevant equations
$$E=-N\frac{d\phi}{dt}$$

$$\phi=BA~\cos \theta$$

3. The attempt at a solution
I think the answer can be (i) and (iii) because there is change in B and it will cause the change in magnetic flux. Am I right?

2. Oct 12, 2009

### rl.bhat

Re: e.m.f

Non-homogeneous field may not change with time. It changes with distance. So by keeping the coil in such field will not produce EMF.

3. Oct 12, 2009

### songoku

Re: e.m.f

Hi Mr rl.bhat

I don't really understand about the field "changing with distance". Maybe it means, for example, the first 2 m the field is 2 T, then for the next 5 m the field is 10 T???

4. Oct 12, 2009

### rl.bhat

Re: e.m.f

According to me, the diverging or converging magnetic field can be treated as non-homogeneous field.

5. Oct 12, 2009

### songoku

Re: e.m.f

Hi Mr. rl.bhat

Now I don't understand the term "converging and diverging magnetic field"....

6. Oct 14, 2009

### songoku

Re: e.m.f

hi Mr. rl.bhat
I have another opinion. Since the field changes with distance (although I don't know what this means) and the distance changes with time, it implies that the field changes with time. Therefore, e.m.f will be produced ???

7. Oct 14, 2009

### rl.bhat

Re: e.m.f

If you consider field due to current carrying solenoid, depending on the direction of the current, the magnetic field from one end is diverging and on the other end it is converging.
If you keep a coil at rest any where near the solenoid, emf will not be induced.
I don't know what is interpretation of homogeneous and non homogeneous field.