Question

A 25 watt - 220 volt bulb and 100 watt
220 volt bulb are connected in parallel
across a 440 volts line, then :

(a). only hundred watt bulb will fuse
(b) only 25 Watt bulb will fuse
(c) both bulb will fuse
(d)none of the bulb will fuse ​

Answer 1

Answer:

both bulb will fuse

Explanation:

A 25 watt - 220 volt bulb and 100 watt

220 volt bulb are connected in parallel

across a 440 volts line, then

25 W  - 220V bulb

R = 220²/25 = 1936 Ω

Current = 220/1936 = 0.11 A

100 W  - 220V bulb

R = 220²/100 = 484 Ω

Current = 0.45 A

Net resistance in Parallel = 1/(1/1936 + 1/484)  = 1936/5 = 387.2 Ω

Total Current with 440V

= 440/387.2

= 1.13 A

Current in 25 W bulb = 0.22 A  > 0.11 A

Current in 100 W bulb = 0.91 A  > 0.45 A

As current will be doubled in both bulbs

Hence both bulb will fuse