NSAA Physics - Thermal Physics and Thermodynamics Flashcards

What is the SI unit of temperature used in thermodynamic equations?

Answer: Kelvin (K)

The Kelvin is the SI unit of thermodynamic temperature, defined so that absolute zero is 0 K.

The zeroth law of thermodynamics states that if object A is in thermal equilibrium with object B, and B is in thermal equilibrium with object C, then:

Answer: A and C are in thermal equilibrium with each other

The zeroth law establishes that thermal equilibrium is transitive — objects sharing a common thermal equilibrium temperature are in equilibrium with each other.

For an ideal gas, the internal energy depends only on:

Answer: Temperature alone

For an ideal gas, intermolecular forces are neglected, so internal energy is purely kinetic and depends only on temperature.

Which law of thermodynamics is the law of conservation of energy?

Answer: First Law

The first law states that the change in internal energy equals heat added to the system minus work done by the system (ΔU = Q − W), embodying energy conservation.

The specific heat capacity of water is 4,200 J kg⁻¹ K⁻¹. How much energy is required to raise 2 kg of water by 5°C?

Answer: 42,000 J

Using Q = mcΔT = 2 × 4,200 × 5 = 42,000 J.

During an isothermal process involving an ideal gas, which quantity remains constant?

Answer: Temperature

An isothermal process occurs at constant temperature; for an ideal gas this also means constant internal energy.

The relationship between the Kelvin and Celsius scales is:

Answer: K = °C + 273

The Kelvin scale is offset from Celsius by 273.15, so K = °C + 273 (to three significant figures).