WAEC - Physics (1988 - No. 39)
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).
64 minutes
32 minutes
8 minutes
2 minutes
1 minute
Explanation
D ∝ l2
E will increase 4 times when current is doubled.
Therefore time will decrease by a factor of 4, which is 1 minute.
E will increase 4 times when current is doubled.
Therefore time will decrease by a factor of 4, which is 1 minute.