Knowee
Questions
Features
Study Tools

An electric heater has two coils. When a current is passed through one of them, water in heater boils in 3 minutes and when current is passed through other one, the water boils in 4 minutes. Then  One/More correct answer(s)A.If both the coils are joined in series, the water in heater boils in 7 minutesB.If both the coils are connected in parallel, the water in heater boils in 127127 minutesC.The resistances of two coils are in the ratio 3 : 4D.If both the coils are joined in series, the water in heater boils in 3.5 minutes

Question

An electric heater has two coils. When a current is passed through one of them, water in heater boils in 3 minutes and when current is passed through other one, the water boils in 4 minutes. Then  One/More correct answer(s)A.If both the coils are joined in series, the water in heater boils in 7 minutesB.If both the coils are connected in parallel, the water in heater boils in 127127 minutesC.The resistances of two coils are in the ratio 3 : 4D.If both the coils are joined in series, the water in heater boils in 3.5 minutes

...expand
🧐 Not the exact question you are looking for?Go ask a question

Solution

The correct answer is C. The resistances of two coils are in the ratio 3 : 4.

Here's why:

The time taken to heat the water is inversely proportional to the power of the heater. The power P of an electric device is given by P = V^2/R, where V is the voltage and R is the resistance. Therefore, the time taken to heat the water is proportional to the resistance of the coil.

Given that one coil heats the water in 3 minutes and the other in 4 minutes, the resistances of the coils are in the ratio 4:3 (not 3:4).

As for the other options:

A. If both the coils are joined in series, the total resistance is the sum of the individual resistances. The time taken to heat the water would be more than 4 minutes but less than 7 minutes.

B. If both the coils are connected in parallel, the total resistance is less than the resistance of the coil with the least resistance. The time taken to heat the water would be less than 3 minutes.

D. If both the coils are joined in series, the water in heater would not boil in 3.5 minutes. As mentioned above, the time taken would be more than 4 minutes.

This problem has been solved

Similar Questions

An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used, same amount of water boils in 10 minutes. If the two coils are connected in parallel then same amount of water will boil in time :-

Heater of an electric kettle is made of a wire of length L and diameter d. It takes 4 minutes to raise the temperature of 0.5 kg water by 40 K. This heater is replaced by a new heater having two wires of the same material, each of length L and diameter 2d. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by 40K?JEE Advanced 2014 (Paper 1)A4 if wires are in parallelB2 if wires are in seriesC1 if wires are in seriesD0.5 if wires are in parallel.

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be :(a) 1 : 2(b) 2 : 1(c) 1 : 4(d) 4 : 1

A current of 2 A is passed through a coil of resistance 75 ohm for 2 minutes. (a) How much heat energy is produced ? (b) How much charge is passed through the resistance?

You have two containers of water.  One container A holds 100 mL and container B holds 2000 mL of water.  What temperature will each container boil?acontainer A will boil at a lower temperature because it has less waterbboth containers will boil at 100°Cccontainer B will boil at a lower temperature because it has more waterdcontainer B will boil at a higher temperature because it has more water

1/1

Upgrade your grade with Knowee

Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.