Approximation involving an exponential function

In summary, the conversation discusses the approximation of exp[gbH/(2kT)] to 1+gbH/(2kT), where gbH/2 <<1. This can be achieved through the Taylor expansion of exp(x) near 0 or by replacing the curved graph with a tangent line.
  • #1
mccoy1
117
0

Homework Statement



I was following a derivation of some laws and I didn't get how they approximate some portion of the expression. That portion/part is exp[gbH/(2kT)]. The book says gbH/2 <<1 and therefore exp[gbH/(2kT)] = 1+gbH/(2kT).

Homework Equations


The Attempt at a Solution


I agree with the value 1, but where did gbH/(2kT) come from? Please help. My understanding is that if gbH/2 is way less than 1, then e.g exp[1.0*10^-15/KT)] = 1.
 
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  • #2
Because it's the Taylor expansion of exp(x) near 0

exp(x) = 1 + x + (x^2)/2 + (x^3)/6 + ...

You can cut the series at any term you would like, however you can't equal it to 1 because there will be no parameter left to give values to...
 
  • #3
You can also get this approximation by replacing the curving graph by a tangent line.
 
  • #4
atomthick said:
Because it's the Taylor expansion of exp(x) near 0

exp(x) = 1 + x + (x^2)/2 + (x^3)/6 + ...

You can cut the series at any term you would like, however you can't equal it to 1 because there will be no parameter left to give values to...

Haa, thank you very much. That didn't pop in my head. Thanks a lot.
 
  • #5
HallsofIvy said:
You can also get this approximation by replacing the curving graph by a tangent line.

Thanks for that.
 

Related to Approximation involving an exponential function

1. What is an exponential function?

An exponential function is a mathematical function in the form of f(x) = ax, where a is a constant and x is the variable. It is characterized by a rapid increase or decrease in value as x increases or decreases, respectively.

2. How do you approximate an exponential function?

To approximate an exponential function, you can use a technique called linearization. This involves finding the tangent line to the curve at a certain point and using that line to estimate the value of the function at that point.

3. What is the purpose of approximating an exponential function?

Approximating an exponential function can be useful in situations where the function is complex or difficult to work with, or when precise values are not needed. It can also be used to make predictions or estimate values for a given input.

4. What are some real-life applications of exponential functions?

Exponential functions are used to model many real-life phenomena, such as population growth, compound interest, radioactive decay, and bacterial growth. They are also commonly used in economics, physics, and engineering.

5. How accurate are approximations of exponential functions?

The accuracy of an approximation of an exponential function depends on the method used and the number of data points used to create the approximation. Generally, the more data points used and the closer they are to the point being approximated, the more accurate the approximation will be.

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