# In an electric soldering iron at a voltage of 120 V, a current of 0.22 A flows.

**In an electric soldering iron at a voltage of 120 V, a current of 0.22 A flows. How much tin taken at a temperature of 293K can be melted in 4 minutes?**

U = 120 V.

I = 0.22 A.

t = 4 min = 240 s.

T = 293 ° K.

Tm = 505 ° K.

λ = 0.59 * 10 ^ 5 J / kg.

C = 230 J / kg * ° K.

m -?

The amount of heat energy Q that is released in the soldering iron can be expressed by the formula: Q = U * I * t.

Since according to the table, the melting point of tin is Tm = 505 ° K, then the required amount of heat Q for melting tin is expressed by the formula: Q = C * m * (Tm – T) + λ * m.

U * I * t = C * m * (Tm – T) + λ * m.

m = U * I * t / (C * (Tmelt – T) + λ).

m = 120 V * 0.22 A * 240 s / (230 J / kg * ° K * (505 ° K – 293 ° K) + 0.59 * 10 ^ 5 J / kg) = 0.06 kg.

Answer: with a soldering iron, you can melt tin m = 0.06 kg.