Question

how to calculate the velocity of the electron ?

Answer 1

Answer:

The speed of electrons

The mass of the electron is m = 9 × 10 -31 kg.

The electronic charge is e = 1.6 × 10 -19 C.

For an electron gun with a voltage between its cathode and anode of V = 100V the electron will have a speed of about v = 6 × 10 6 m/s. (Relativistic effects have not been taken into account.)

Answer 2

Answer:

The answer depends on the situation .(1): In metallic conductor we have free electron ‘gas’ and we can regard that gas approximately as ideal gas. Then, we can use kinetic theory of gas. This theory relates kinetic energy per particle with temperature by the formula (1/2)mv^2=(3/2)kT, where k is Boltzmann constant.(2): In a conductor we define drift velocity also. We know that when voltage is applied between two ends of a wire,an electric field E=V/l is established in the wire . Now, electron has acceleration=Ee/m. Also, during their motion electrons collied with the ions at the lattice sites or are scattered by the ions in the continuously varying fields of vibrating ions.If T(av)is average time period between two consecutive collisions with ions, the velocity that electron acquires while going from one ion to another ion for the next collision is termed as drift velocity and is given by v(d)=(Ee/m)T((av).Finally,the current density is given by J(vector)=nev(d)(vector). From current density we can find drift velocity .(3): When electron is accelerated in potential difference V, it’s kinetic energy becomes (1/2)mv^2=eV. Here and also in above collision discussion we have taken initial velocity zero.(4): In Bohr model ,we can write 2pir(n)=nh/mv. Now, radius of nth orbit r(n)=(n^2h^2.epsilon zero)/(pi.Ze^2.m). Combining these two formulae we can find electron velocity in hydrogen atom according to Bohr’s model.