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

July 26, 2021 | education

| **The electric heater of tram cars operates at a current of 112 A and a voltage of 550 V. At what speed does a tram move if the engines create a traction force of 3.6 Kn, and their efficiency is 77%.**

To find out the speed of the tram, we will use the formula: ηд = Рп / Рзатр = Ftyag * V / (U * I), from where we express: V = U * I * η / Ftyag.

Data: U – operating voltage (U = 550 V); I is the current in the electric motor of the tram (I = 112 A); ηд – efficiency of tram engines (ηд = 77% = 0.77); Ftyag – created traction force (Ftyag = 3.6 kN = 3.6 * 10 ^ 3 N).

Let’s perform the calculation: V = U * I / (ηд * Ftyag) = 550 * 112 * 0.77 / (3.6 * 10 ^ 3) ≈ 13.18 m / s.

Answer: The tram must move at a speed of 13.18 m / s.