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An electric kettle has two coils of same...

An electric kettle has two coils of same power . When one coil is switched on , it takes `15 min` to boil water , and when the second coil is switched on , it takes `30 min`. How long will it take to boil water when both the coils are used in `i`. Series and `ii`. parallel?

A

`9:2`

B

`2:9`

C

`4:5`

D

`5:4`

Text Solution

Verified by Experts

The correct Answer is:
A
`t_(S)=t_(1)+t_(2),t_(P)=(t_(1)t_(2))/(t_(1)+t_(2))`
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