Need help with this question Questions 3 There are 8.5 x 105 conduction electron

Question

Need help with this question

Questions 3 There are 8.5 x 105 conduction electrons per cubic meter in copper (n-8.5 x 10 A piece of cooper wire which has a diameter of 0.5 mm carries a current of 0.26 amps. a) Determine the drift speed of electrons in the wire b) On average an electron in copper (at 20°C) will enter into a collision every 2.6 x 10-14 s. This is called the mean free time. How far will an average electron drift in between collisions? It drifts in the direction of the electrostatic force that acts on it. In which direction is that relative to the field? c) If the electric field in the wire has magnitude 0.85 V/m N/C) how much work (on average) does the electrostatic force do on an electron in between collisions? How much kinetic energy does the electron gain?

Explanation / Answer

Current = (drift velocity)*n*(charge of electron)*(area of cross section)

Area of cross section = pi*r^2 = pi * (0.25*10^-3)^2

drift velocity = I/(n*e*A) = 0.26 / (8.5 * 10^28 * 1.6 * 10^-19 * pi * (0.25*10^-3)^2)

drift velocity = 9.7 * 10^-5 m/s

mean free time = 2.6*10^-14 s

Distance moved in mean free time = 9.7*10^-5*2.6*10^-14 = 25.22*10^-19 meters = 2.522*10^-18 meters

Charge of electron is negative

So force on electron is opposite to the direction of field

Work done by electric fiend E in moving a charge q through a distance r = q*E*r = 1.6*10^-19 * 0.85*2.522*10^-18

Work = 3.43*10^-37 Joules

KE gained by electron = work done on it by field = 3.43*10^-37 Joules

Related Questions

Navigate

• Browse (All)
• Browse N
• Subjects

---