# Homework Help: Total Energy and Voltage Change for an Electron

1. Apr 25, 2009

### blahblahblahh

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

Alright so, there are two different parts that I am having trouble with for this question.

The first problem I need to calculate the total energy of a group of 12 electrons that each individually have a potential of 3 V. This is all that is given for the first part.

For the second part, I need to find the voltage change that occurs for an electron if the temperature gets increased by 175K.

2. Relevant equations

For the first part, I believe the correct equation to use would be:

E = qV

For the second part, the equation that I think would be correct is:

V = kT/q

3. The attempt at a solution

First part:

Since there are 12 electrons, I simply thought that adding up the 12 individual electrons would give the total energy for the group with the given potential. Therefore, I did:

E = 12*q*V = 12(1.602 x 10^-19 C)(3 V) = 5.767 * 10^-18 Joules

Second part:

Using the equation given and the voltage given from part 1, I thought the correct approach was to use this equation:

V_change = (k(T + 175))/q - kT/q = 175k/q = ((175 K)(1.38 x 10^-23 J/K))/(1.602 x 10^-19 C) = .015 Volts

The main things that I am worried about are the sign in part 1, the equations used for part 1 and part 2 since I'm not sure they're the correct ones, and also for the first part I'm not sure if simply multiplying by 12 since there are 12 electrons correctly gives the total energy for all of the electrons. I guess I'm mainly looking for confirmation that the equations I used were correct and that simply multiplying qV by 12 to get the total energy for a group of 12 electrons is allowed.

Thank you for any help or confirmation you can give me.