How is a memristor different from a resistor

[iampaul]

I read that the memristor is described by the equation dφ=Mdq. If both sides are divided by dt, then dφ/dt=Mdq/dt.
But dφ/dt=V and dq/dt=I. Then V=MI which is ohm's law. Isn't the constant M just the same as resistance?

 

[mfb]

M is a function of charge flown (and therefore a function of time as well), that is the point of the memristor. A resistor would have a constant M.

(Mdq)/dt is not the same as M(dq/dt).

 

[iampaul]

So M is not a constant unlike R, L, and C? I read that the memristor was predicted due to the symmetry of the equations for R, L and C. If M is not constant with respect to time, doesn't that make the memristor the odd one out o the four, so that there is still no symmetry?

 

[mfb]

M is not the constant. The constant is how M changes with charge, in the similar way as the voltage at a capacitor changes with charge.

 

[SredniVashtar]

In this 1971 paper by Leon O. Chua, you can find the formulae spelt out (p. 511)

www.cpmt.org/scv/meetings/chua.pdf