Question

a block of iron mass 60kg must be heated from 20 degrees Celsius to 300 degrees Celsius. the specific heat capacity of iron is470J/kg k. the effeciencyof the system is 71%. the available supply voltage is. 230V. the process must be completed within 2 hours. if electricity from eskom is presentlyR1, 77 kilometers per hour. determine the value of current drawn from the source and the total cost of the process

Answer 1

Part a

P=VI

$\frac{W}{t}=VI$

$\frac{mc \triangle T}{t}=VI$

$I=\frac{mc \triangle T}{Vt}=\frac{60 *470* 573-293 }{230 *2*60*60}=4.768 kW$

Part b

$1kWh = R1, 77$

$4.768kWh = \frac{R177*4.768}{1}=R843.96$