Question

A fluid contained in a horizontal cylinder fitted with a frictionless leak proof piston is continuously agitated by a stirrer passing through the cylinder cover. The diameter of the cylinder is 50 cm and the piston is held against the fluid due to atmospheric pressure equal to 100 kPa. The stirrer turns 8000 revolutions with an average torque of 1.5 N-m. If the piston slowly moves outwards by 60 cm, determine the net work transfer to the system.
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Answer 1

Answer:

Given :

Heat gained = 4.5 × 10⁵ J

Heat released = 2 × 10⁵ J

To Find :

Percentage efficiency of steam engine and work done per cycle..

Solution :

❒ Efficiency of a heat engine/steam engine is given by, η = 1 - (Q₂ / Q₁)

Where,

η denotes efficiency

Q₂ denotes heat released to the sink

Q₁ denotes heat extracted from the source

By substituting the given values;

➛ η = 1 - (Q₂ / Q₁)

➛ η = 1 - (2 × 10⁵ / 4.5 × 10⁵)

➛ η = 1 - 0.44

➛ η = 0.56

Percentage efficiency = 56%

❒ Work done per cycle :

We know that work done is measured as the change in energy.

➠ W = Q₁ - Q₂

➠ W = (4.5 × 10⁵) - (2 × 10⁵)

➠ W = 2.5 × 10⁵ J