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What is the difference between curly and derivative (d) sign

  1. Mar 19, 2015 #1
    Dear All,

    Please see the image below in attachment where Energy is function of K. I want to understand how is it possible to understand the last expression ( dE = ? ). Additionally, what is the difference between curly and derivative (d) sign ?

    Many thanks to the mentors on this forum
    Best wishes
     

    Attached Files:

  2. jcsd
  3. Mar 19, 2015 #2

    RaulTheUCSCSlug

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    Gold Member

    the "curly" derivative (d) sign is called a partial derivative, and is when you only take derivative of a function that has multiple variables. It works very similar to a regular derivative.
     
  4. Mar 19, 2015 #3

    RaulTheUCSCSlug

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    Gold Member

    The last expression is just taking the partial derivative of E with respect to each k, and summing them up since the derivative of the sum is the sum of derivatives!
     
  5. Mar 19, 2015 #4
    This subject is covered in multivariable calculus
     
  6. Mar 20, 2015 #5
    Thanks RaulTheSCSlug, kindly mention what is the physical meaning of the quantity ∂E/∂k1 * dk1 .

    Best wishes
     
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