Question

An alpha particle is projected vertically upward with a speed of 3.0 × 10⁴ km s⁻¹ in a region where a magnetic field of magnitude 1.0 T exists in the direction south to north. Find the magnetic force that acts on the α-particle.

Answer 1

Given:
Upward speed of the alpha particle, v = 3 × 10⁴ km/s = 3 × 10⁷ m/s

Magnetic field, B = 1.0 T

The direction of the magnetic field is from south to north.

Charge of the alpha particle, q = 2e,

where e is the charge of an electron.

q = 2 × 1.6 × 10⁻¹⁹ C,

Magnetic force acting on the α-particle,

`vecF = qvecv xx vecB  sin 90^circ`

= `2xx1.6xx10^-19xx3xx10^7 xx 1 xx 1`

= `9.6xx10^-12` N , towards west 

The direction of magnetic force can be found using Fleming's left-hand rule.