Question

Электрический чайник имеет две обмотки.Если включить в сеть первую,то вода закипает через 15 мин,а если включить вторую то через 30 мин.Через сколько времени закепит чайник,если обе обмотки включить парарельно.Напряжение в сети равно 220 В

Answer 1

30 минут и чайник скипит

Answer 2

Calculation of the Boiling Time

To determine the boiling time of the kettle when both coils are connected in parallel, we need to consider the individual boiling times of each coil.

According to the given information, when the first coil is connected, the water boils in 15 minutes, and when the second coil is connected, the water boils in 30 minutes.

To calculate the boiling time when both coils are connected in parallel, we can use the concept of electrical power.

Electrical Power and Boiling Time

The electrical power consumed by an electrical device can be calculated using the formula:

Power (P) = Voltage (V) x Current (I)

In this case, the voltage in the circuit is given as 220 V.

The power consumed by each coil can be calculated using the formula:

Power (P) = Voltage (V) x Current (I)

Let's assume the current through the first coil is I1 and the current through the second coil is I2.

When the first coil is connected, the power consumed is:

P1 = 220 V x I1

When the second coil is connected, the power consumed is:

P2 = 220 V x I2

Since the boiling time is directly proportional to the power consumed, we can write the following equation:

Boiling Time1 / Boiling Time2 = Power1 / Power2

Substituting the values, we get:

15 min / 30 min = P1 / P2

Simplifying the equation, we have:

1/2 = P1 / P2

Now, let's solve for P1 in terms of P2:

P1 = (1/2) x P2

Calculation of Boiling Time when Both Coils are Connected

When both coils are connected in parallel, the total power consumed is the sum of the powers consumed by each coil:

Total Power = P1 + P2

Substituting the values, we get:

Total Power = (1/2) x P2 + P2

Simplifying the equation, we have:

Total Power = (3/2) x P2

Since the boiling time is inversely proportional to the power consumed, we can write the following equation:

Boiling Time1 / Boiling Time_Total = Power_Total / Power1

Substituting the values, we get:

15 min / Boiling Time_Total = (3/2) x P2 / P1

Since we know that P1 = (1/2) x P2, we can substitute this into the equation:

15 min / Boiling Time_Total = (3/2) x P2 / [(1/2) x P2]

Simplifying the equation, we have:

15 min / Boiling Time_Total = 3

Now, let's solve for Boiling Time_Total:

Boiling Time_Total = 15 min / 3

Simplifying the equation, we have:

Boiling Time_Total = 5 min

Therefore, when both coils are connected in parallel, the kettle will boil the water in 5 minutes.

Conclusion

When both coils of the electric kettle are connected in parallel, the boiling time is reduced to 5 minutes.