The electric motor of the crane operates under a voltage of 360 V. What useful work does the electric

| April 29, 2021 | education

The electric motor of the crane operates under a voltage of 360 V. What useful work does the electric motor do in 50 s, if the efficiency of the installation is 50%.

U = 360 V.

t = 50 s.

Efficiency = 50%.

I = 20 A.

Apol -?

Efficiency The efficiency of a crane is determined by the formula: Efficiency = Apol * 100% / Azat, where Apol is the crane’s useful work, Azat is the spent crane work.

The spent crane work will be the work of the electric current in its engine. We express the work of the current by the Joule-Lenz law: Azat = I * U * t, where I is the current in the crane motor, U is the current voltage, t is the operating time of the crane.

Efficiency = Apol * 100% / I * U * t.

Apol = I * U * t * efficiency / 100%.

Apol = 20 A * 360 V * 50 s * 50% / 100% = 180,000 J.

Answer: the crane has done useful work Apol = 180,000 J.



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