The greater voltage drop occurs across the 60-watt bulb if it is series with a 100-W bulb. If the two bulbs are in parallel. the voltage drops across each are identical.
Work Step by Step
The 100-watt bulb has less electrical resistance. More power for the same voltage means that the current is greater. By Ohm’s law, more current for the same voltage means that the 100-W filament has less electrical resistance. In series, the voltage drop across each lamp is proportional to its resistance (Rule 5, page 443). When connected in parallel, the voltage across each bulb is the same (Rule 1, page 444).