Question

An electron has been accelerated from rest through a potential difference of 1000 V. a. What is its kinetic energy, in electron volts? b. What is its kinetic energy, in joules? c. What is its speed?

Answer 1

Answer:

a. 1000ev.

b. 1.602×10⁻¹⁶ Joules.

c. 3.52× 10¹⁴  m/s

Explanation:

(a)

Kinetic Energy of the electron in Electron volt = eV

Ek = eV...................... Equation 1

Where Ek = Kinetic Energy of the electron in electron volt, V = potential difference of the electron, e = charge of electron.

Given: V = 1000 V,

Substituting these values into equation 1,

Ek = 1000 eV

(b) Kinetic Energy in Joules

Ek = eV

Where e = 1.602 × 10⁻¹⁹ joules, V =1000 V,

Ek = 1.602 × 10⁻¹⁹×1000

Ek = 1.602×10⁻¹⁶ Joules.

(c) Ek = 1/2mv²

m = √(2Ek/m)........................... Equation 2

Where m = mass of the electron, v = velocity of the electron.

Given: Ek = 1.602×10⁻¹⁶

Constant: m = 9.11×10⁻³¹ kg.

Substituting into equation 2

v = √(2×1.602×10⁻¹⁶/9.11×10⁻³¹)

v = 3.52× 10¹⁴  m/s