Question

If it takes 8 minutes to boil a quantity of water
electrically, how long will it take to boil the same
quantity of water using the same heating coil
but with the current doubled​

Answer 1

Step-by-step explanation:

The power P depends on current i as,

P=i

2

R

Hence P∝i

2

i.e. when current is doubled, power increases

four times.

Also,

Energy, E=P×t

For same quantity of water E is same, therefore,

t∝

P

1

Since in the second case, power P'=4P⟹t

′

=

4

t

=2 minutes .