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A charged particle carrying charge 1 μC is moving with velocity (2i + 3j + 4k) m/s. If an external magnetic field of (5i + 3j − 6k) × 10⁻³ T exists in the region where the particle is moving then the force on the particle is F × 10⁻⁹ N. The vector F is-

1. (1) −3.0i + 3.2j − 0.9k
2. (2) −300i + 320j − 90k
3. (3) −30i + 32j − 9k
4. (4) −0.30i + 0.32j − 0.09k

Correct answer: (3) −30i + 32j − 9k

Solution

v x B = (-30, 32, -9)*10^-3. F = q(v x B) = 10^-6 * (-30,32,-9)*10^-3 = (-30,32,-9)*10^-9 N, so F = -30i + 32j - 9k.

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