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# Name of 2nd time derivative of charge q?

## Name of 2nd time derivative of charge q?

(OP)
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.

### RE: Name of 2nd time derivative of charge q?

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
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### RE: Name of 2nd time derivative of charge q?

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
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### RE: Name of 2nd time derivative of charge q?

(OP)
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").

### RE: Name of 2nd time derivative of charge q?

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]

### RE: Name of 2nd time derivative of charge q?

Rise time?

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

### RE: Name of 2nd time derivative of charge q?

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

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

### RE: Name of 2nd time derivative of charge q?

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.

### RE: Name of 2nd time derivative of charge q?

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

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