Question

If two bulbs rated 25 W - 110 V and 100 W - 110 V is connected in series to a 220 V supply then which bulb will fuse first?

• A. 25 W bulb will fuse
• B. 100 w bulb will fuse
• C. both will fuse
• D. both will not fuse

Answer 1

The correct option is A 25 W bulb will fuse

The first light bulb will take nearly all of the voltage drop, while the second light bulb will take nearly none

As you can see, the voltage drop across the first light bulb is approximately 211𝑉211V, while the voltage drop across the second light bulb is only approximately 9𝑉9V.

This means that the first light bulb will be very bright and the second light bulb simply won’t turn on.

In practice, the voltage drop across the first light bulb will be too much, and it will be destroyed, effectively creating the equivalent of an open switch in your circuit.