Lorentz force direction reverses for negative charges like beta particles

Steps:

• Current in the wire consists of electrons (negative charges) moving opposite to conventional current direction.
• Force on wire equals Lorentz force on these electrons: F = q (v × B), with q < 0 and v opposite conventional current.
• Beams fired parallel to conventional current means v parallel to conventional current, so for beta (q < 0), effective q v parallel to electron motion in wire.
• Thus, beta experiences force same direction as wire; alpha (q > 0) opposite; neutrons (q = 0) none.

Why B is correct:

• Beta particles are negatively charged electrons; their force matches wire's per Lorentz force law when v aligns with effective charge motion.

Why the others are wrong:

• A: Alpha positive, force opposite wire's; neutrons neutral, no force.
• C: Includes neutrons (no force) and alpha (opposite force).
• D: Beta-particles same as B, but option specifies only beta without context match.

Final answer: B