Awell-insulated electric water heater warms 131 kg of water from 20.0°c to 51.0°c in 31.0 min. find the resistance (in ω) of its heating element, which is connected across a 240 v potential difference. 6.34 correct: your answer is correct. ω (b) what if? how much additional time (in min) would it take the heater to raise the temperature of the water from 51.0°c to 100°c? 28 incorrect: your answer is incorrect. min (c) what would be the total amount of time (in min) required to evaporate all of the water in the heater starting from 20.0°c?

Explanation:

Heat required to warm the water from 20 degree to 51 degree

= mct

= 131 x 4150 x ( 51 - 20 )

= 16853150 J

Power of heating element

= v² /R

Heat generated in 31 min

= (v² / r ) x 31 x 60 = 16853150

r = (240 x 240 x 31 x 60) / 16853150

6.35 ohm

In this case heat required will change so time will also change

Heat required =

131 x 4150 x ( 100-51  )

= 26638850 J

If time required be t hour

Energy consumed

Power x time

=  (v² / r ) x t  x 60 = 26638850

t  = 26638850 x 6.35 / (240 x 240 x 60 )

= 48.95 h

Heat required to evaporate water at 100 degree

= mass x latent heat

= 131 x 2260000

= 296060000 J

Total heat required

= 296060000 + 26638850 + 16853150

= 339552000 J

time required = 339552000 x 6.35 / (240 x 240 x 60 )

= 623.88 h .

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27