What kind of work does the floor polisher’s engine do in a time equal to 30 minutes

What kind of work does the floor polisher’s engine do in a time equal to 30 minutes if it consumes a 220 V circuit, a current of 1.25 A, and its efficiency is 80%.

These tasks: t (duration of the polisher’s work) = 30 min (in SI t = 1800 s); U (voltage in the circuit) = 220 V; I (current) = 1.25 A; η (polisher motor efficiency) = 80% (0.8).

The work that the floor polisher engine will perform in 30 minutes of operation can be expressed from the formula: η = Apol / Az = Ap / (U * I * t), whence Apol = U * I * t * η.

Let’s make a calculation: Apol = 220 * 1.25 * 1800 * 0.8 = 396 * 10 ^ 3 J (396 kJ).

Answer: In 30 minutes of operation, the engine of the floor polisher performed work at 396 kJ.