Question

A 0.5 m length of current-carrying wire kept perpendicular to a magnetic field of
magnitude 200 mT experiences a force of 1.5 mN. What is the current flowing in the
wire.

Answer 1

Ampere force acts on a conductor with current in a magnetic field

$F=B \cdot I \cdot l$

where will we write

$I=\frac {F}{B \cdot l}=\frac {1.5}{200 \cdot 0.5}=15 mA$