What should a voltmeter that is attached to three batteries, each measuring 1.5 volts read:

The answer depends on the arrangement of the batteries either parallel or series.

If the three batteries are connected in parallel, the voltmeter will read the same voltage as the individual battery (I.e, the combine voltage will remain 1.5 Bolts)

While

If the batteries are connected in series, and are correctly connected together from positive to negative, the combine voltages will increase by adding individual battery voltage together. So for three 1.5 Volts batteries, the total voltages will be 4.5 Volts.

Explanation:

Parallel connected

Vp = 1.5 Volts

Series connection

Vs = 1.5 + 1.5 + 1.5 = 4.5Volts

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.