Question

There will be no force experienced if

• A. two parallel wires carry currents in the same direction
• B. two parallel wires carry currents in the opposite direction
• C. a positive charge is projected between the pole pieces of a bar magnet
• D. a positive charge is projected along the axis of a solenoid carrying current

Answer 1

The correct option is D a positive charge is projected along the axis of a solenoid carrying current

Two parallel wires carrying currents in same direction attract each other.
Two parallel wires carrying currents in opposite direction repel each other.
A positive charge is projected between the pole pieces of bar magnet feels a force = $q(\overrightarrow{V}\times \overrightarrow{B})$ which is non zero since angle between V and B is non-zero.
A positive charge projected along the axis of a solenoid carrying current feels no force because in solenoid B is along the axis so $\overrightarrow{V}\times \overrightarrow{B}$ is zero.