Verifying Equation is Dimensionless

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In summary, the conversation discusses converting an equation with various symbols into a dimensionless form. The new dependent variables are defined as TAq(y,τ)= p(y/α,Tτ) and new dimensionless independent variables are τ(tau) := t/ T and y:= αx. To verify that the equation is dimensionless, all terms must be expressible as combinations of the new dimensionless variables. The equation L(x,t) = A g(t) h(τ(t)) + d(y,τ) is confirmed to be dimensionless as the terms can be expressed as such. The symbols d and h(τ) represent arbitrary, dimensionless functions.
  • #1
onie mti
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i am given this equation

View attachment 2323
where L is the rod of length when light signals are applied at one end (x=0)
D>0 is the diffusivity T>0 a time constant, A amplitude of the applied signal(carriers per second), g(t) the oscillatory behavior of the signal and α> 0 a material constant.

i need to change the equation above into one where all the symbols are dimensionless.
where
T is taken as the unit time
α^-1 the unit of length
AT the carrier density.

i am given that
the new dependent variables q=q(y,τ) is defined TAq(y, τ)= p(y/α,Tτ)
my work

from the above information, i defined new dimensionless independent variables
τ(tau) := t/ T(time)
y:= αx(position)

now how do i verify that the equation below is dimensionless and explain the symbols d and h(τ)
View attachment 2324
 

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L(x,t) = A g(t) h(τ(t)) + d(y,τ)To verify that the equation is dimensionless we need to check if all of the terms can be expressed as a combination of the new dimensionless independent variables y=αx and τ=t/T. The term A g(t) h(τ(t)) can be expressed as A(T/AT)g(Tτ)h(τ). This is a combination of the new dimensionless independent variables and therefore it is dimensionless. The term d(y,τ) can also be expressed as d(αy,Tτ) which is again a combination of the new dimensionless independent variables and therefore it is also dimensionless. Thus, we can conclude that the equation L(x,t) = A g(t) h(τ(t)) + d(y,τ) is indeed dimensionless. The symbols d and h(τ) refer to some arbitrary functions which are dimensionless.
 

FAQ: Verifying Equation is Dimensionless

What does it mean for an equation to be dimensionless?

When an equation is dimensionless, it means that all of the terms in the equation have the same units, and therefore, the units cancel out. This allows for the equation to be used universally, regardless of the unit system being used.

How do you verify if an equation is dimensionless?

To verify that an equation is dimensionless, you must carefully examine each term in the equation and ensure that the units are consistent and cancel out. If the units do not cancel out, then the equation is not dimensionless.

Why is it important to have dimensionless equations in science?

Dimensionless equations are important in science because they allow for easier comparison and analysis of different physical quantities. They also make it easier to generalize equations and apply them to different systems and scenarios.

Can an equation be partially dimensionless?

No, an equation is either dimensionless or not. If even one term in the equation has units, then the entire equation is considered to have dimensions.

How can you convert a non-dimensional equation into a dimensional one?

To convert a non-dimensional equation into a dimensional one, you must reintroduce the appropriate units for each term in the equation. This can be done by multiplying or dividing the non-dimensional equation by a conversion factor with the appropriate units.

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