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23.6 and 23.7

Now that we can find the resulting electric field from a given charge distribution, we can study how other charges or dipoles will respond.

The idea is simple, the force on the charge is

\vec{F} = q\vec{E}

If the charge is negative, the force is in the opposite direction to the electric field.

If the electric field is uniform (near an infinite plane of charge), the force will be constant and we can use our usual constant force and constant kinematics from Phys 211.

\vec{F}=m\vec{a}

If the force is perpendicular to the velocity, the charge will still accelerate, it will turn.

Dipoles

The motion of a dipole is interesting. The opposite force on each end of the dipole create a torque that wants to alight the dipole in the direction of the E field. If the E field is uniform, the dipole will experience no net force. In an non-uniform field, there will be a small force.

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