Re: rise of direct current in absence of self induction

By definition, yes the current rise would be instantaneous in a circuit without inductance. Of course no such circuit can exist! Even a vacuum has inductance of 1.257 microhenrys per meter (permeability) and a capacitance of 8.85 picofarads per meter. (permittivity)

From these two constants, the permeability and the permittivity we get the speed of light and the impedance of space. A Farad is a amp-second per volt, and a Henry is a volt-second per amp. Each constant has electrical and space-time units. Cancelling the space-time units leaves electrical impedance.

The characteristic impedance of free space, also called the Zo of free space, is the square root of the ratio of the permeability of free space (ľo) in henrys per meter (H/m) to the permittivity of free space (eo) in farads per meter (F/m):

Zo = (ľo/eo)^1/2

= [(1.257 x 10-6 v*s/a*m)/(8.85 x 10-12 a*s/v*m)]^1/2

= 377 ohms (approximately)

The exact value of the Zo of free space is 120 pi ohms

Likewise, cancelling the electrical units leaves space and time, commonly expressed as speed.

Vo = (ľo eo)^-1/2

= [(1.257 x 10-6 v*s/a*m)*(8.85 x 10-12 a*s/v*m)]^-1/2

= 300,000,000 meters/sec (approximately)

So any circuit, defined as a closed loop where current flows, has some non-zero size in space, and therefore some non-zero inductance.

So how does an inductor know what the back EMF is? Simply the available voltage. Think of the inductor initially as an open circuit. All the available voltage appears across the open circuit, as i builds up according to V = L * di/dt the back EMF approaches zero, with a time constant proportional to the inductance.

Even in the absence of particles like electrons, spacetime has inductance and capacitance. Seems like the mass/charge ratio of the electron could possibly add a bit more inductance, but I have never heard of such inertial effects being expressed as an inductance.