# Charged particle hitting electric field at angle?

1. Dec 30, 2015

### Intle

If I have an electric field between a cathode and an anode, are there electric field lines between the plates?
If yes, what happens if a charged particle enters the field at an angle? Is the force acting on the particle reduced?

2. Dec 30, 2015

### Staff: Mentor

Electric field lines are just a graphic means to visualize the electric field. So if there is an electric field, field lines can be used to illustrate it.
What do you think? What does the direction of a field line represent?

3. Dec 30, 2015

### lychette

get clear in your mind what is meant by an electric field. You have an ANODE and a CATHODE....which direction is the electric field (assuming the anode and cathode are connected to the appropriate power supply)
what does this tell you about FORCES on charged particles?

4. Dec 30, 2015

### Staff: Mentor

Reduced relative to what?
There is a general formula for the force on charged particles in an electric field. Does the motion of the particle go into that formula?

5. Dec 30, 2015

### Intle

I apologize for not being specific enough. I am asking this question because when looking at the magnetic fields and particle motion withing that field the equation, F=q*v*B*sin() can be used to take into account the particle's initial velocity vector hitting the magnetic force vector at an angle. I am wondering if there is a similar equation for electric fields since the only equation I have found so far is F=E*q which to my understanding basically just says that it does not matter if there is an initial velocity or not and/or at what angle the charged particle hits the field.
I was referring to a negatively charged electrode when I said cathode, and a positively charged electrode when I said anode. So more specifically I was thinking of a situation where the cathode is heated and electrons escape the cathode and travel towards the anode, gaining energy as they are subject to the electric force.

6. Dec 30, 2015

### Staff: Mentor

Correct, it does not matter, the force is always the same.

7. Dec 31, 2015

### Intle

So why i
So why is that different in a magnetic field?

8. Dec 31, 2015

### Staff: Mentor

Because that's the way the magnetic field works, by definition.

In general, the electromagnetic force on a charge at a specific location has a part which depends on the velocity of the charge, and a part which does not. For historical reasons, we split the electromagnetic force into two parts: the magnetic force which depends on velocity, and the electric force which does not.

9. Dec 31, 2015

### ZapperZ

Staff Emeritus
I think that you are utterly confused about the Lorentz force law.

There are TWO parts to this force law, as can be seen from the two separate terms in it:

F = qE + q v x B

Your question, i.e. a charge moving in between two plates (assuming uniform electric field), involves NO external magnetic field. So here, only

F = qE

is relevant. This problem is no different than, say, a projectile motion in a uniform gravity (i.e. first year intro physics).

Is this clear?

Zz.

10. Dec 31, 2015