Where should a third charge of +1.5 μC be placed between two charges (-4 μC and +3 μC) so that it experiences no net force?

To find the point where the third charge experiences no net force, we need to apply Coulomb's Law. The net force on the third charge ($Q_3$) will be zero when the magnitude of the force exerted by $Q_1$ on $Q_3$ is equal to the magnitude of the force exerted by $Q_2$ on $Q_3$, and these forces are in opposite directions.

Given charges:
$Q_1 = -4 \mu C = -4 \times 10^{-6} C$
$Q_2 = +3 \mu C = +3 \times 10^{-6} C$
$Q_3 = +1.5 \mu C = +1.