# Dimensional Analysis and Power enthropy

1. May 1, 2012

### dan4loriel

1. The problem statement, all variables and given/known data

how do i deduce the dimension of the following using dimensional analysis

Power enthropy, surface charge density, inductance, permitivity, radius of gyration

tried deducing the dimension of power like this:

p=work done/time
work done w= force x distance
=MLT e^-2 L
=ML e^T e^-2

substitute for power P= ML e^2 T e^ -2/T = ML e^ 2 T e^ -2

=ML e^ 2 T e^ -3

anyhelp will be appreciated

2. May 1, 2012

### BruceW

I'm not sure what the 'e' is supposed to mean? Do you mean p = ML2T-3 ? If this is what you meant, then you are correct for the dimensions of power.

3. May 1, 2012

### dan4loriel

yes that is what i mean can you give me a clue on the dimension of enthrophy th3n

4. May 1, 2012

### BruceW

do you mean entropy? And to figure out its dimensions, you just need to do the same kind of thing you did with power. You knew that power is energy divided by time, and you knew the dimensions of energy and time, so you just substituted them into the equation to get the dimensions of power. So what equations do you know which involve entropy?

5. May 2, 2012

### dan4loriel

yes entropy, and i think dq=du+dw involves entropy am i right?

6. May 2, 2012

### BruceW

ah, well not that equation exactly. but there is an equation which relates a small change in entropy to dq

7. May 2, 2012