# How to change an electric field?

1. Oct 26, 2012

### nukeman

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

I am working on a research question, I can't quite understand it.

Lets say I want to create 3 different electric fields, varrying in type and strength?

Lets say I wanted to see how how my cat acted in 3 different electric fields? Don't worry, my cats participation in my research projects are limited to knocking my pens off my table and playing with them :)

How can I do this?

2. Relevant equations

3. The attempt at a solution

2. Oct 26, 2012

### Simon Bridge

You arrange for different charge distributions.

eg. you can rub a bit of amber for different lengths of time: the field about the amber each time will be different. You can connect a capacitor to a battery for different lengths of time and the field between the plates will be different each tie. And so on.

3. Oct 26, 2012

### nukeman

Simon.

So can I give you a idea, and you tell me how I would construct something?

Lets say I want to test 2 groups of flies, and I want to see what changes to the fly occur when inside a different electric field.

How would I construct such a box?

4. Oct 27, 2012

### Simon Bridge

The details depend on the sort of field you want.
Do you know how to put a charge on something?

For an easy field - look up "parallel plate capacitor".

5. Oct 27, 2012

### nukeman

This is where I am having trouble.

Here is what I am trying to do.

(Very crudely speaking)... I want to stick a bunch of lab flies in a box, or any space where they cant really get out of, with a certain electric field. And also I want to put a different group of lab flies in another box with a different electric field.

My hope is that flies activity level will be affected by electric field, as I think an electric field will interact with its brain's electric field.

6. Oct 27, 2012

### Simon Bridge

Did you look up "parallel plate capacitor"?
Put your box between the plates.

Do you know how to put a charge on something?

7. Oct 27, 2012

### nukeman

Oh sorry.

Umm, sort of. I know you can rub a wool with a rod to apply a charge.

Yes, I looked up parallel plate capacitor. I see 2 different wires connected to the plates which are connected to whatever is generating the positive charge.

So, I could make one of these, and simply put the box in the middle? Or connect it to the box? (plastic box?)

Is there a way to measure the electric field in the box?

Thanks so much for the help!

8. Oct 27, 2012

### Simon Bridge

No worries. I'm being deliberately obtuse because this is the homework section: if I just told you what to do then I'd have don't your homework for you.

Charging stuff?
Great - it is the rod that gets charged. The more you rub the more the rod is charged. There is an electric field around the rod. Put the rod in the cage with the flies and watch.

Yes.[/quote]Is there a way to measure the electric field in the box?[/quote]Yes - there are meters for that - or you can calculate it from knowing the voltage and the dimensions of the plates.

Note: there are three ways to change an electric field:
1. change it's strength
2. change it's shape
3. change it's direction

The capacitor field is very parallel while the rod field is radial. You can reverse the direction of the capacitor field by reverse-biasing the plates. You change the strength of the rod field by rubbing it different amounts and the capacitor field by changing the voltage.

But it sounds to me that you don't know what an electric field is, or what electric charge is.
You should review those parts of your course.