# Solve Physics Question: 3.0g Copper Penny & 38uC Positive Charge

• Jodi
In summary, the conversation discusses a question about a copper penny with a positive charge of 38 microcoulombs and the fraction of electrons it has lost. The person asking for help shares their method and asks for assistance with the correct answer. Two other individuals provide hints and suggestions for solving the problem.
Jodi
Hi; Could somebody please help me with this question: A 3.0g copper penny has a postive charge of 38uC. What fraction of its electrons has it lost?
The method I tried was: (3g/63.55g) x 6.02E23 x A(what I'm solving for) = 38xE-6. Than I took my answer and divided it by 29. However this will not give me the correct answer, and the correct answer is 1/(3.5E9). Can somebody please help me. Thank you so much.

Look at your units. You have a dimensionless number on the left side and coulombs on the right side. You need to factor in the charge on an electron.

Try a more systematic approach:

- How many electrons does it take to make up $$-38\mbox{\mu C}$$ charge? (hint: use the electron charge)

- How many electrons are in 3.0g copper (when neutral)? (29 per copper atom)

Thanks...

Thanks guys, I figured this one out.

## 1. How does the mass of a 3.0g copper penny affect its charge when it is given a positive charge of 38uC?

The mass of an object does not affect its charge. The charge on an object is determined by the number of electrons it has gained or lost, not its mass. Therefore, the charge on the penny would still be 38uC regardless of its mass.

## 2. How can the charge on a copper penny be measured?

The charge on a copper penny can be measured using an electroscope. This device detects the presence and magnitude of electric charge by using thin metal leaves that repel each other when a charge is applied. The more the leaves repel, the higher the charge on the object.

## 3. What is the unit for electric charge?

The unit for electric charge is Coulomb (C). It is named after the French physicist Charles-Augustin de Coulomb and is defined as the amount of charge that passes through a cross-section of a conductor in one second when a current of one ampere is flowing.

## 4. How does a positive charge affect a copper penny?

A positive charge on a copper penny will cause the penny to become positively charged as well. This is because the penny will gain some of the positive charge from the source, resulting in a net positive charge on the penny.

## 5. Can a copper penny hold a charge for a long period of time?

No, a copper penny cannot hold a charge for a long period of time because it is not a good conductor of electricity. This means that the charge on the penny will dissipate quickly, resulting in the penny returning to its neutral state.

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