Verified Solution • 2025–26 Session
moderate
QAIPMT-2003-Ph-2756: NEET 2003 Physics - Class 12 AIPMT-2003-Ph-2756 Solution: An electric kettle has two heating coils. When one of the coils …
An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be
Multiple Choice Options
- A 8 minutes
- B 4 minutes
- C 25 minutes
- D 15 minutes
Step-by-Step Verified Solution
Let R 1 and R 2 be the resistance of the two coils and V be the voltage supplied.
Effective resistance of two coils in parallel = R 1 R 2 R 1 + R 2
Let H be the heat required to begin boiling in kettle.
Then H = Power _ time = V 2 t 1 R 1 = V 2 t 2 R 2
For parallel combination, H = V 2 ( R 1 + R 2 ) t p R 1 R 2
_ 1 t p = ( t 2 + t 1 t 2 t 1 )
_ t p = t 2 t 1 t 2 + t 1 = 10 _ 40 10 + 40 = 8 minute