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.