JIPMER2009PhysicsMagnetic Effects of Current
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B . If V and B are kept constant, the ratio ( charge on the ion mass of the ion ) will be proportional to
Options
- A1 R
- B1 R^2
- CR^2
- DR
Correct answer
B. 1 R^2
Step-by-step solution
The radius of the orbit in which ions moving is determined by the relation as given below m v^2 R =q v B where m is the mass, v is velocity, q is charge of ion and B is the flux density of the magnetic field, so that q v B is the magnetic force acting on the ion, and m v^2 R is the centripetal force on the ion moving in a curved path of radius R . The angular frequency of rotation of the ions about the vertical field B is given by = v R = q B m =2 v where v is frequency. Energy of ion is given by or aligned E & = 1