Question

(i) Consider a beam of charged particles moving with varying speeds. Show how crossed electric and magnetic fields can be used to select charged particles of a particular velocity?

(ii) Name another device/machine which uses crossed electric and magnetic fields. What does this machine do and what are the functions of magnetic and electric fields in this machine? Where do these field exist in this machine? Write about their natures.

Answer 1

(i) If we adjust the value of \(\overrightarrow{E}\) and \(\overrightarrow{B}\) such that magnitude of the two forces are equal, then total force on the charge is zero and the charge will move in the fields undeflected. This happen when

qE = Bqv or \(v=\frac{E}{B}\)

(ii) Name of the device: Cyclotron 

It accelerates charged particles or ions. 

Electric field accelerates the charged particles. 

Magnetic field makes particles to move in circle. 

Electric field exists between the Dees. 

Magnetic field exists both inside and outside the dees. 

Magnetic field is uniform. 

Electric field is alternating in nature.