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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.
Solution
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.
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