(a) The magnitude of the minimum magnetic field is 1.467 T.
(b) The direction of the minimum magnetic field will be eastwards.
F = qvB
mg = qvB
B = mg/qv
where;
B = (1.98 x 10⁻⁴ x 9.8) / (3.5 x 10⁻⁸ x 3.78 x 10⁴)
B = 1.467 T
The magnetic field will be directed towards the negative charge. Thus, the direction of the minimum magnetic field will be eastwards.
Thus, the magnitude of the minimum magnetic field is 1.467 T and the direction is eastwards.
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