What mass of steel taken at the melting temperature can be melted using a heating element with an efficiency of 40%
What mass of steel taken at the melting temperature can be melted using a heating element with an efficiency of 40% if at a voltage of 100V a current of 10A passes through it. The melting time is half an hour.
Given:
n = 40% = 0.4 is the efficiency of the heating element;
U = 100 Volts – mains voltage;
I = 10 Amperes – the value of the current in the circuit;
t = 30 minutes = 1800 seconds – time span;
q = 78000 J / kg – specific heat of melting of steel.
It is required to determine m (kilogram) – what mass of steel can be melted.
Let’s find the power of the electric current:
W = I * U = 10 * 100 = 1000 watts.
Then the work of the electric current will be equal to:
A = W * t = 1000 * 1800 = 1800000 Joules.
Taking into account the efficiency of the heating element:
A1 = A * n = 1,800,000 * 0.4 = 720,000 Joules.
Then the mass of steel will be equal to:
m = A1 / q = 720,000 / 78,000 = 720/78 = 9.2 kilograms (the result has been rounded to one decimal place).
Answer: You can melt steel weighing 9.2 kilograms.