# Why don't electrons accelerate in a circuit?

In a circuit, electric field exerts force on electrons, so they must accelerate. Every text book I have read, points that electrons move with a constant drift velocity. How can this happen? Does Newton's law not apply there?

• May 22 at 13:48

Yes Newton's law is applied here, and the electrons accelerate in response to the electric field. However, the electrons also undergo collisions with the atoms of the conductor, so on an average, they acquire an initial velocity of zero just after each collision. The electrons then acquire a final velocity $$\vec v_f$$ before the next collision and the average value of this final velocity is termed as the drift velocity, which is found to be a constant value, simply because the average time interval τ between each collision (called the relaxation time) is very small
• @MathKeepsMeBusy From the sources I've read, the average value of the vector $\vec v_f$ is the vector $\vec v_d$ that is directed parallel/antiparallel to the electric field, but you may be right. The Drude model for electrical conduction has it's flaws anyway, especially because the particles in consideration are very small. May 22 at 14:26