Conversion units mystery. Am I wrong?

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AI Thread Summary
The discussion centers on calculating charge (Q) using the formula Q = W/V, where W is work and V is potential difference. The potential difference is given as 140mV, and the work required is 280μJ. It is emphasized that converting the potential difference to volts and work to joules is necessary for accurate calculations. A user points out that dividing mJ by mV results in coulombs, not milliCoulombs, and suggests simplifying the approach by converting all units to standard SI units before performing the calculations. The conversation highlights the importance of unit consistency in physics problems.
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Homework Statement


The potential difference between two points is 140mV. If 280μJ of work are required to move a charge Q from one point to the other, what is Q?

Homework Equations


Q = W/V

The Attempt at a Solution


http://imgur.com/FDaQfb9
 
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Hi, welcome to PF!

Convert the potential difference to volts, and the work to joules. Dividing joules with volts, you get coulombs for the charge. mJ/mV is also coulomb.

ehild
 
You are assuming that mJ divided by mV gives mC. That's wrong, it gives C. In general, you have overcomplicated things too much. Just convert everything into J and C, compute the result, then convert it to any units you want.
 

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