A very long straight wire carries a current i. At the instant when a charge +Q at point P has velocity $\overrightarrow{\mathrm{v}}$ , as shown, the force on the charge is

At point P, magnetic field will be inside the plane of the paper. 

$\overrightarrow{\mathrm{F}}=\mathrm{q}\left(\overrightarrow{\mathrm{v}}\times \overrightarrow{\mathrm{B}}\right)$

So, magnetic force on the charge will be in vertically upward direction parallel to the conductor, i.e, along OY direction.