Question

A 1500 electrical kettle is used to boil 1.0 L of water which was originally at 10 degrees Celsius it takes 5.0 min to boil what is the efficiency of the kettle

Answer 1

Q=mc(100-t)+mL
Where t=10 – starting temperature
For water from table:
C=4200
L=22.6*10⁵
M=vp=1000kg/m³*0.001m³=1kg
Q=1*4200*90+1*22.6*100,000=2638000dj -needed energy to boil water.
A=1500*5*60=4500000 work what is done.
K=Q/A=59%