# Solve Electrical Work Problem: 15V to 5V

• punjabi_monster
In summary, the conversation is about a problem where the answer is not agreeing with a friend's answer. The problem involves calculating the work done on a system as its voltage drops from 15 V to 5 V. The homework statement also includes the edge length of 1 cm and the water permittivity. The equations used are for electrical potential, charge, and permittivity. The attempted solution resulted in a work of -6.954 * 10^-11 J. The question about the system in question reveals that it is a hypothetical electrochemical cell and the edge length of 1 cm can be applied to any geometry.
punjabi_monster
Hi there. I was attempting this problem but my answer is not agreeing with my friends.
He got 1.4 *10^-7
Any help will be appreciated.

## Homework Statement

Calculate the work done on a system if its voltage drops from 15 V to 5 V.
edge length= 1 cm
water permittivity e=78.54e

## Homework Equations

dwelec = (elec pot.)dQ
Q=(elec pot)2ed
e=78.54 * eo

## The Attempt at a Solution

w = (elec pot.)f (Qf - Qi)
=(elec pot.)f (2ed)[(elec pot.)f - (elec pot.)i]
=(5V)(2(78.54)(8.854*10^-12)(0.001)(5V-15V)
= -6.954 * 10^-11 J

What is the system in question?

its an hypothetical electrochemical cell.

Geometry? Edge length of 1 cm can be appliead to anything.

## 1. How do I calculate the electrical work when the voltage changes from 15V to 5V?

To calculate the electrical work, you can use the formula W = Q x ΔV, where W is the work done, Q is the charge, and ΔV is the change in voltage. In this case, you would plug in 15V for the initial voltage and 5V for the final voltage.

## 2. What units should I use for the electrical work calculation?

The unit for electrical work is joules (J). It is the same unit used for energy.

## 3. Can I use any other formula to calculate the electrical work?

Yes, there are other formulas that can be used to calculate electrical work, such as W = I x ΔV, where I is the current in amperes (A). However, for this specific problem, using the formula W = Q x ΔV would be the most appropriate.

## 4. Is there a specific order to plug in the values for the electrical work calculation?

Yes, it is important to plug in the initial voltage first and then the final voltage. This will ensure that you get a positive value for the work done. If you plug in the final voltage first, you will get a negative value, indicating that work is being done on the system instead of by the system.

## 5. Can I use this formula for any change in voltage?

Yes, this formula can be used for any change in voltage. It is a general formula for calculating electrical work. However, it is important to make sure that the units for voltage are consistent (e.g. both in volts or both in millivolts), and that the charge is in coulombs (C).

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