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NEET2003PhysicsAlternating CurrentActual

An electric kettle has two heating coils. When one of the coils is connected to a.c. source, the water in the kettle boils in 10 minute. When the other coil is used the water boils in 40 minute. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be:

Options

  1. A8 minute
  2. B4 minute
  3. C25 minute
  4. D15 minute

Correct answer

A. 8 minute

Step-by-step solution

Here Q= V^2 R₁ t₁= V^2 R₂ t₂ aligned & = V^2 R t & 1 R = 1 R₁ + 1 R₂ & Q V^2 t = Q V^2 t₁ + Q V^2 t₂ & 1 t = 1 t₁ + 1 t₄ & t= t₁ t₂ t₁+t₂ & = 10 40 10+40 =8 ~min & aligned

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