A three - way light bulb has three brightness settings ( low , medium , and high) but only two filaments . The two filaments are arranged in three settings, when connected across a `120 V` line and can dissipate `60 , 120 and 180 W`. Answer the following questions:
(i) Higher resistance filament only works for `60 W`
ii. Low resistance filament works for `120 W`
iii.Low resistance filament works for `60 W`
iv. High resistance filament works for `120 W`
v. Low and high resistance filaments in parallel for `180 W`
vi. Low and high resistance filament in series for `180 W`

Options

A. `I,ii, and v` are correct
B. `I, ii , and vi` are correct
C. `iii, iv, and v` are correct
D. `iii , iv , and vi` are correct

Answer

A

Explanation

The `60 W` bulb will be of higher resistance. If only switch `1` is closed , `120 W` bulb will glow. If only switch `2` is closed , `60 W` bulb will glow . If both the switches are closed, both bulbs will glow with total illumination of `180 W`.
When the filament of higher resistance ( of `60 W` bulb) burns out, then for two settings ( either `1` is closed or both are closed) power dissipated will be `120 W`.