Name of 2nd time derivative of charge q?

Question

Name of 2nd time derivative of charge q?

dculp1 (Mechanical)

(OP)

22 Jun 16 09:30

For charge q, the first time derivative dq/dt is the current i. The 2nd time derivative is d^2q/dt^2. Is there a name for this?

By analogy, for a mechanical system the displacement is u and the first time derivative du/dt is the velocity. The 2nd time derivative d^2u/dt^2 is the acceleration.

Thanks,
Don C.

xnuke (Electrical) · Answer 1 · 2016-06-22 14:18:03

I suppose you could refer to current as charge velocity and its rate of change as charge acceleration, but no one I know uses those terms, or any other term for rate of change of current for that matter.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

IRstuff (Aerospace) · Answer 2 · 2016-06-22 15:19:58

It's not named because there is no physical concept that requires it. Acceleration only exists by name because it means something physically useful and represents fundamental concepts embodied in F = m*a or x = 1/2 a*t^2. There is no corollary for for charge and current. Maxwell's Equations and Ampere's Law only require charge and current.

TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

dculp1 (Mechanical) · Answer 3 · 2016-06-22 17:39:51

IRstuff --

The 2nd time derivative of charge is used for the voltage drop across an inductor -- V = L d^2q/dt^2 = L di/dt. I'd like to refer to this derivative textually in the same manner as one would refer to "acceleration" (i.e., without having to continually refer "2nd time derivative of charge" or "2nd time derivative of displacement").

IRstuff (Aerospace) · Answer 4 · 2016-06-22 18:13:41

Yes, I forgot about that. But, that's just referred to as "ell dee eye dee tee" and there is no specific physics symbol for that quantity, so no name either.

TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

Comcokid (Electrical) · Answer 5 · 2016-06-22 23:31:32

di/dt does not not have a specific name. In switch-mode power it will be referred to as the current slope, current ramp, as most times it has a periodic saw-tooth appearance. Sometimes, if not periodic, it may be referred to as the current waveform, current change, change in current, delta I, etc.

Electrical engineering doesn't have position, velocity, accelleration, but we're just jerks. [bigsmile]

waross (Electrical) · Answer 6 · 2016-06-23 12:05:14

Rise time?

Bill
--------------------
"Why not the best?"
Jimmy Carter

VEBill (Military) · Answer 7 · 2016-06-23 12:15:56

It'd be related to the inverse of rise time.

"Current rate of change" is the only name that I recall.

sreid (Electrical) · Answer 8 · 2016-07-13 18:42:35

You should coin a name for this. You have a need for a new word. Others might make suggestions

As you mention in mechanical systems there is position, velocity, acceleration, jerk, and Ping.

VEBill (Military) · Answer 9 · 2016-07-13 23:31:03

'Snap', 'Crackle' and 'Pop' are sometimes used at the higher end of the derivatives of position scale.

Answer 10

[Post Deleted]

Come Join Us!

Posting Guidelines

Name of 2nd time derivative of charge q?