# How Do Electric Charge and Fields Influence Forces and Charges?

• Dx
I'll try to stick with hints from now on.Originally posted by Dx I see! But that's sure a lot of typing I must do.:wink:I'll comply from this day forward.Don't worry about that. We don't expect you to type your solutions. What we do expect is that you have attempted the problem and have shown your work. It doesn't have to be pretty. It doesn't have to be complete. Just show what you've done so far. That's all we ask.Originally posted by Dx You did it exactly as i did, I got 24F and it was marked wrong on my test. Please understand I am serious about cheating also and
Dx
Hello,

I have some missed test questions that I still don't understand. Can anyone please explain these.

1)
Two chrged objects atrract each other with a force F. What happens to the F between them if one is doubled, the other is tripled and the separation distance between their centers is reduced to 1/4 its original value? the force is now equal to

16F
3/8F
96F

2)What is the charge on 1kg of protons?

1C
9.6 x 10^7 C
6x10^26C

3)A copper penny has mass 3g. A total of 4x10^12 electrons are transfored from one nuetral penny to another. if the electrostatic force of attraction between the pennies is equal to the weight of a penny, what is the separation between them?

31cm
35cm
37cm

4) How can a negatively charged rod charge an electroscope negatively? Is it by conduction because its not induction.

can anyone gimme their answer and how they derived it since I missed it I provided the remaining test answers to help you choose from. Please any help is appreciated as always.

Thanks!
Dx

As you know, I don't like posting complete solutions here, especially when the poster hasn't shown any work. It doesn't teach you anything when someone shows you how to solve a problem. So, I am going to give you hints so that you can figure them out for yourself.

Originally posted by Dx
1)
Two chrged objects atrract each other with a force F. What happens to the F between them if one is doubled, the other is tripled and the separation distance between their centers is reduced to 1/4 its original value? the force is now equal to

16F
3/8F
96F

First, note that all 3 changes serve to increase the force, so you can eliminate choice #2 immediately.

Second, take the expression for Coulomb's law:

F=kq1q2/r2

Now let q1-->2q1
and q2-->3q2
and r-->(1/4)r

Make the substitutions in Coulomb's law and answer the question.

2)What is the charge on 1kg of protons?

1C
9.6 x 10^7 C
6x10^26C

Easy as pie.

You need the mass and charge of a proton, and from there it's a simple unit conversion.

3)A copper penny has mass 3g. A total of 4x10^12 electrons are transfored from one nuetral penny to another. if the electrostatic force of attraction between the pennies is equal to the weight of a penny, what is the separation between them?

31cm
35cm
37cm

They give you the magnitude of the electric force. It equals mpennyg. They also give you the charge on each penny. Use Coulomb's law:

F=kq1q2/r2

The only unknown is r, and that is what they are asking for.

4) How can a negatively charged rod charge an electroscope negatively? Is it by conduction because its not induction.

There's no hint I can think of that doesn't give it away. You'll have to do the research on it.

I don't understand the first question.

Is it asking: What is the force between the two chrages if the charge of one particle is double and the other trippled and their distance of separation cut by a quarter.

Set it up:

F = k * q^2/r^2
Ff = k * 6q^2/(1/4r)^2

Mentor Edit: Rest of solution removed.

I apprciate anyone who helps out in this forum, but let's stick to giving hints. A few complete solutions to problems have been posted lately, and I'm cracking down!

Last edited by a moderator:
Originally posted by frankR
I don't understand the first question.

Is it asking: What is the force between the two chrages if the charge of one particle is double and the other trippled and their distance of separation cut by a quarter.

Set it up:

F = k * q^2/r^2
Ff = k * 6q^2/(1/4r)^2

Mentor Edit: Rest of solution removed.

I apprciate anyone who helps out in this forum, but let's stick to giving hints. A few complete solutions to problems have been posted lately, and I'm cracking down!

You did it exactly as i did, I got 24F and it was marked wrong on my test.

Please understand I am serious about cheating also and don't believe in it fellas, please understand your help is appreciated and ALL I AM ASKING is how you solved it. Thats it! Besides I can't learn if I don't know what's going on and I hate typing all my work just to get a few sentences of "HINTS". So ty to understand I am not about cheating I just want to understand why I missed those questions and I appreciate everyones help. Tom, you always do a great job of explaining, i thank you, sir.
TY!
Dx

Last edited by a moderator:
Originally posted by Dx
Please understand I am serious about cheating also and don't believe in it fellas, please understand your help is appreciated and ALL I AM ASKING is how you solved it.

Cheating is not the issue. The issue is that, if we simply hand the solution and an explanation to you, you aren't learning anything. You have to figure these things out for yourself, and if you post your work we can help you with that (This is the Homework Help forum, after all).

Post your work, and we will tell you where you went wrong.

I see! But that's sure a lot of typing I must do.
I'll comply from this day forward.

Originally posted by Dx
You did it exactly as i did, I got 24F and it was marked wrong on my test.

Dx

Ummm:

What's 6/(1/4)2?

Opps! Edit

Last edited:
Originally posted by frankR
Mentor Edit: Rest of solution removed.

I apprciate anyone who helps out in this forum, but let's stick to giving hints. A few complete solutions to problems have been posted lately, and I'm cracking down!

Ummmm: Sorry, I wasn't really thinking about that. I usually don't post whole solutions.

## 1. What is electric charge?

Electric charge is a fundamental property of matter that describes the amount of electrical energy that a particle possesses. It can be either positive or negative and is measured in units of coulombs (C).

## 2. How is electric charge created?

Electric charge can be created by adding or removing electrons from an atom, which changes its overall charge. It can also be transferred from one object to another through processes such as friction, induction, or conduction.

## 3. What is an electric field?

An electric field is a region in space around a charged object where the force of the electric charge can be felt. It is represented by lines of force that point away from positive charges and towards negative charges.

## 4. How is the strength of an electric field measured?

The strength of an electric field is measured in units of newtons per coulomb (N/C). It can be calculated by dividing the force on a test charge by the magnitude of the test charge.

## 5. How do electric charges interact with each other?

Electric charges can interact with each other through the electric force, which can either attract or repel depending on the charge of the particles. Like charges repel each other, while opposite charges attract.

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