To melt the ice on the wire of the electric railway, an electric current was passed through the wire

To melt the ice on the wire of the electric railway, an electric current was passed through the wire. How much ice (0 ° C) will melt every minute? Line voltage 500 V, current 400 A, electric heating efficiency 70%.

The efficiency of electric heating can be expressed in the formula:
η = Q / A, where η is the efficiency (η = 70%), Q is the amount of heat that goes to melt the ice, A is the work of the el. current.
Q = λ * m, where λ is the specific heat of melting of ice (λ = 335 kJ / kg = 335 * 10 ^ 3 J / kg), m is the mass of ice.
A = I * U * t, where I is the current strength (I = 400 A), U is the voltage (U = 500 V), t is the operating time of the el. current (t = 1 min = 60 s).
η = Q / A = λ * m / (I * U * t).
Ice mass:
m = η * I * U * t / λ = 0.7 * 400 * 500 * 60 / (335 * 10 ^ 3) ≈ 25 kg.
Answer. You can melt 25 kg of ice every minute.