Question

A 500w electric heater is used to heat 1kg of water without energy loses.The specific heat capacity of water is 4.2 kJ/kg k.what is the time taken to heat the water from 25°C to 75°C.
solution please.​

Answer 1

Answer:

7min

Explanation:

time taken to heat water from 25 to 75 degree Celsius is 7 min

Answer 2

Given: A 500 Watt electric heater is used to heat 1 kg of water without energy loss. The specific heat capacity of water is 4.2 kJ/kg.

To find: Time taken to heat the water from 25° C to 75°C

Explanation: Mass of water(m)= 1 kg

Specific heat(S)= 4.2 kJ/kg

Initial temperature= 25°C = 25+273 K

= 298 K

Final temperature= 75° C = 75+273 K

= 348 K

Temperature difference (T) = 348-298 = 50 K

Heat required to change temperature is given by: mST = 1* 4.2* 50 kJ

= 210 kJ

= 210000 J( since 1kJ= 1000 J)

Heat given by 500 W heater= Power* time where power= 500 W

=> Heat= 500*t

=> 210000= 500t

=> t = 210000/500 s

= 420 seconds

Therefore, the heater will take 420 seconds to heat water from 25°C to 75° C.