GENERAL KNOWLEDGE

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

  • A. 64 minutes
  • B. 32 minutes
  • C. 8 minutes
  • D. 2 minutes
  • E. 1 minute ✓

 

The answer to the question is: E. 1 minute

To calculate how long it will take to boil the same quantity of water using the same heating coil but with the current doubled, we can use the formula:

Q = I² × R × t

Where:

Q = heat energy required to raise the temperature of the water

I = current 

R = resistance of the heating coil

t = time

Assuming that the resistance of the heating coil remains constant, we can use the equation:

Q1 = I² × R × t1

Q2 = (2I)² × R × t2 (current doubled)

Since the quantity of water and the heating coil are constant, we can equate Q1 and Q2

I² × R × t1 = (2I)² × R × t2

I² × R × t1 = 4I² × R × t2

Solving for t2 = I² × R × t1 / 4I² × R

t2 = t1 / 4

Given that, t1 = 4 minutes

t2 = 4 minutes / 4 = 1 minute

Therefore, if it takes 4 minutes to boil a quantity of water electrically with a certain current, it will take 1 minute to boil the same quantity of water using the same heating coil but with the current doubled.

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