Question

What is the magnetic force experienced by a negatively charged particle of $1.0C$ that is moving upward at a velocity of $2.0\times {10}^{3}m/s$ in a magnetic field of strength $4.0\times {10}^{4}T$, directed into the page?

• A. $0.8N$ to the left
• B. $0.8N$ to the right
• C. $2.0\times {10}^{7}N$ to the left
• D. $2.0\times {10}^{7}N$ to the right
• E. $5.0\times {10}^{6}N$ to the left

Answer 1

Answer: (B)

$0.8N$ to the right

Magnitude of magnetic force $F$ on a particle having a charge $q$ , moving with velocity $v$ in a magnetic field $B$ is given by ,

$F=qvB\sin \theta$ where $\theta =$ angle between $v$ and $B$ ,

now given $q=1.0C$ , $v=2.0\times {10}^{3}m/s$ , $B=4.0\times {10}^{-4}T$ , and $\theta =90$ (as velocity is upward and field is directed into page)

therefore $F=1.0\times 2.0\times {10}^3\times 4.0\times {10}^{-4}\sin 90$

or $F=0.8N$

we apply Fleming's left hand rule in the given condition (taking direction of current opposite to the velocity of particle as it is a negative particle) then the direction of force will be to the right .
B is given by