A question about units in equation: Dimensional analysis

In summary, the conversation discusses the equation for electron mobility and the issue of matching the units in the equation. It is suggested to use dimensional analysis and reduce everything to MKSA units, instead of using V which stands for M⋅L2⋅T−3⋅I−1. It is also mentioned that the presence of an electron's charge needs to be considered in the equation with voltage. Help and further clarification on the topic is requested.
  • #1
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This question is about the matching the unites in an equation.

The equation for an electron mobility is given by m^2/V.S.
However substituting the units in the equation, doesn't yield the unit of mobility [m^2/V.S]. I have done the simplification using mks units and didn't come up to m^2/V.S. Have a look at the attached file, and help is appreciated.

Thanks
GH
 

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  • #2
Welcome to PF.

Dimensional analysis is the truth. The equations may be wrong, or you may be confusing derived units with the fundamental MKSA system.

Try to reduce everything to MKSA. Avoid V, which is = M⋅L2⋅T−3⋅I−1

An electron has charge, where does that appear in the equation with voltage?
https://en.wikipedia.org/wiki/Dimensional_analysis
 

Related to A question about units in equation: Dimensional analysis

What is dimensional analysis?

Dimensional analysis is a mathematical method used to check and convert the units of physical quantities in equations. It involves using the dimensions (such as length, time, mass, etc.) of each term in an equation to ensure that both sides of the equation have the same units.

Why is dimensional analysis important?

Dimensional analysis is important because it allows scientists to check the validity of equations and calculations. It also helps with unit conversions, which are essential for comparing and understanding data from different sources.

How do I use dimensional analysis?

To use dimensional analysis, you need to identify the physical quantities involved in the equation and their corresponding dimensions. Then, you can manipulate the units algebraically to ensure that they cancel out and leave only the desired units on the final answer.

Can dimensional analysis be used for all types of equations?

Yes, dimensional analysis can be used for all types of equations, as long as the equations involve physical quantities with units. This method is especially useful for complex equations with multiple variables.

What are some common mistakes to avoid in dimensional analysis?

Some common mistakes to avoid in dimensional analysis include forgetting to include all the units in an equation, not using the correct conversion factors, or using incorrect dimensions for a physical quantity. It is important to double-check your work and be consistent with units throughout the calculation.

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