NEET-XII-Physics
04: Moving Charges And Magnetism
- #12In Exercise 4.11 obtain the frequency of revolution of the electron in its circular orbit. Does the answer depend on the speed of the electron? Explain.
Ans : Magnetic field strength, B = 6.5 × 10-4 T
Charge of the electron, e = 1.6 × 10-19 C
Mass of the electron, me = 9.1 × 10-31 kg
Velocity of the electron, v = 4.8 × 106 m/s
Radius of the orbit, r = 4.2 cm = 0.042 m
Frequency of revolution of the electron = ν
Angular frequency of the electron = ω = 2``\pi``ν
Velocity of the electron is related to the angular frequency as:
v = rω
In the circular orbit, the magnetic force on the electron is balanced by the centripetal force. Hence, we can write:
This expression for frequency is independent of the speed of the electron.
On substituting the known values in this expression, we get the frequency as:
Hence, the frequency of the electron is around 18 MHz and is independent of the speed of the electron.