# 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.