# B How Electromotive Force is Produced by Electric Generator?

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1. Oct 5, 2016

### mo0nfang

at 5:42 - What is Electromotive Force? Why does it make electrons move (make electric current) in one direction?

Last edited: Oct 5, 2016
2. Oct 5, 2016

### BvU

That force is called the Lorentz force, which google.

3. Oct 8, 2016

### mo0nfang

Electromagnetic Induction @1:40 <--- Why protons group themselves at the top and electrons at the bottom?

4. Oct 8, 2016

### .Scott

In that video, the electrons (-) are moving to the top. It's because of the direction of the magnetic field. It could have been either way.

5. Oct 8, 2016

### Staff: Mentor

Again, it is the Lorentz force, of which you are well aware.

6. Oct 9, 2016

### David Lewis

How concentrated energy is in an electric field. Lorentz force moves charged particles to positions of higher potential energy.
Divide the energy by the amount of charge and you get electromotive force.

7. Oct 10, 2016

### vanhees71

To argue with a "potential" is misleading in this case since the Lorentz force is not a potential force but reads
$$\vec{F}=q \left (\vec{E}+\frac{\vec{v}}{c} \times \vec{B} \right),$$
and thus the correct electromotive force in Faraday's Law of induction in integral form is
$$\mathcal{E}(t)=\int_{C} \mathrm{d} \vec{r} \cdot \left [\vec{E}(t,\vec{x})+\frac{\vec{v}(t,\vec{x})}{c} \times \vec{B}(t,\vec{x}) \right ]=-\frac{1}{c} \dot{\Phi}_B,$$
where $$\vec{v}(t,\vec{x})$$ is the velocity field of the path $C$.

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