# The electric motor of tram cars operates at a current of 112A and a voltage of 550V

September 14, 2021 | education

| **The electric motor of tram cars operates at a current of 112A and a voltage of 550V How fast does a tram move if the engines create a traction force of 3.6 kN and their efficiency is 70%**

To find out the speed of the specified tram, we apply the formula: η = Npol / Nzatr = Ftyag * V / (I * U), from where we express: V = I * U * η / Ftyag.

Data: I – operating current (I = 112 A); U – effective voltage (U = 550 V); η – efficiency of electric motors of cars (η = 70% = 0.7); Ftyag – the thrust force of the engines (Ftyag = 3.6 kN = 3.6 * 10 ^ 3 N).

Let’s perform the calculation: V = I * U * η / Ftyag = 112 * 550 * 0.7 / (3.6 * 10 ^ 3) ≈ 11.98 m / s.

Answer: The indicated tram must move at a speed of 11.98 m / s.

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