Question

Give an account of magnetic Lorentz force.

Answer 1

(a)

(b)

Direction of the Lorentz force on

(a) positive charge

(b) negative charge

1. An electric charge q is moving with velocity `vec"v"` in the magnetic field `vec"B"`, experience a force called magnetic force `vec"F"_"m"`  deduced by Lorentz.
   `vec"F"_"m" = "q" (vec"v" xx vec"B")` ....(1)
   `vec"F"_"m"` = qvBsin θ ……………(2)

   Equations (1) & (2) implies

2. `vec"F"_"m"` is directly proportional to the magnetic field `vec"B"`.
3. `vec"F"_"m"` is directly proportional to the velocity `vec"V"`.
4. `vec"F"_"m"` is directly proportional to sine of the angle between the velocity and magnetic field.
5. `vec"F"_"m"` is directly proportional to the magnitude of the charge q.
6. `vec"F"_"m"` is always perpendicular to `vec"V" and vec"B".`
7. The direction `vec"F"_"m"` on negative charge is opposite to the direction of `vec"F"_"m"` on positive charge.
8. If velocity `vec"v"` of the charge is along magnetic field, `vec"F"_"m" = 0.`