It takes 4 minutes to boil a quantity of water electrically. How long will it take to boil same quantity of water using the same heating coil but with the current doubled? (neglecting any external heat loss).

  • A 64 minutes
  • B 32 minutes
  • C 8 minutes
  • D 2 minutes
  • E 1 minute
waec 1988physics

The correct answer is E. 1 minute

D ∝ l2

E will increase 4 times when current is doubled.

Therefore time will decrease by a factor of 4, which is 1 minute.

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