ECAT MCQs

The ideal-gas equation gives PV=nRT.
PV=2×8.31×300 = 4986 J.

Using ΔU=Q-W for work done by the gas.
ΔU=500-200 = 300 J.

Take Q=-400 J and work done by the gas W=-100 J.
ΔU=Q-W=-400-(-100)=-300 J.

Efficiency is work output divided by heat input.
300/1000×100 = 30%.

Energy conservation gives W=Qin-Qout.
W=1200-800 = 400 J.

Refrigerator COP is heat removed divided by work input.
COP=600/200 = 3.

The change in internal energy equals heat added minus work done by the system.
It is an energy-balance statement.

Convert 5 minutes to 300 seconds and use E=Pt.
E=100×300 = 30,000 J.

Real processes have a preferred direction and generate entropy.
Some heat must be rejected by a cyclic heat engine.

In SHM, the restoring influence grows with displacement.
The acceleration always points toward the equilibrium position.

Kelvin temperature is Celsius temperature plus about 273.
27+273 = 300 K.

Amplitude measures the largest excursion from equilibrium.
It affects energy but not the ideal SHM period.