Chapter 35, Problem 44A

A three-way bulb uses two filaments to produce three levels of illumination (50 W, 100 W, and 150 W) using a 120-V socket. When one of the filaments burns out, only one level of illumination (50 W or 100 W) is available. Are the filaments connected in series or in parallel?

To determine

The type of connection for filaments.

Explanation of Solution

Introduction:

In series connection, the bubs are connected by the end to end connection of one bulb to other bulb. If one bulb in the connection burns out, then the current in complete combination stops due to open circuit.

The one level of illumination of bulb is available after burning of one filaments. So, the filaments are connected in parallel. If filaments are connected, then the circuit become open circuit due to burning of one filament and no level of illumination after burning.

Conclusion:

The filaments are connected in parallel connection.