IB Physics HL Theme B: The particulate nature of matter questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type

Multiple choice Written

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Question 1

Paper 2Easy7 marks

A student models the apparent brightness $b$ of a star at different distances $d$ assuming the star’s luminosity $L$ remains constant. The relationship is

b=\frac{L}{4\pi d^2}

where $b$ is measured in $\mathrm{W\,m^{-2}}$ $L$ in $\mathrm{W}$ and $d$ in $\mathrm{m}$

Figure 1 shows the modelled apparent brightness as the distance from the star is changed.

(a)

Use Figure 1 to determine the apparent brightness of the star when $d=1.0\times10^{16}\,\mathrm{m}$

[1]

(b)

Using your answer to (a), calculate the luminosity of the star.

[3]

(c)

Use Figure 1 to determine the apparent brightness when $d=2.0\times10^{16}\,\mathrm{m}$

[1]

(d)

State the factor by which the apparent brightness changes when the distance increases from $1.0\times10^{16}\,\mathrm{m}$ to $2.0\times10^{16}\,\mathrm{m}$ and explain this change using the relationship given.

[2]

Question 2

Multiple choiceEasy1 mark

A fixed amount of ideal gas changes between the two states shown. The labelled pressures are absolute; $p$ is a positive pressure and $V$ is a positive volume. Which expression gives $T_B/T_A$

Show answer and explanation

Answer: A. For a fixed amount of ideal gas, $PV/T=\text{constant}$ so $T_B/T_A=P_BV_B/(P_AV_A)$ Substituting the values shown gives $(3p)(2V)/[(2p)(V)]=3$ the temperature ratio is dimensionless.
B: reverses the state ratio, giving $T_A/T_B=1/3$
C: omits the volume ratio and uses pressure alone, giving $3/2$
D: omits the pressure ratio and uses volume alone, giving $2$
Remember: compare the products $PV$ when finding temperature ratios for a fixed amount of ideal gas.

Question 3

Paper 2Hard10 marks

A cyclic engine operates between two thermal reservoirs at $480\ \mathrm{K}$ and $300\ \mathrm{K}$ The engine, both reservoirs and an ideal mechanical work store form an isolated assembly. The engine returns to its initial state each cycle, and the work store’s entropy does not change.

For a reservoir at constant temperature, its entropy change is $\Delta S=Q/T$ where $Q$ is the energy received by the reservoir.

(a)

State the Clausius form and the Kelvin form of the second law of thermodynamics.

[2]

(b)

In one proposed cycle, the engine receives $1.20\ \mathrm{kJ}$ from the $480\ \mathrm{K}$ reservoir, transfers $0.50\ \mathrm{kJ}$ to the $300\ \mathrm{K}$ reservoir and delivers $0.70\ \mathrm{kJ}$ to the work store.

Assess whether this proposed cycle is consistent with energy conservation and the second law.

[4]

(c)

The engine continues to receive $1.20\ \mathrm{kJ}$ from the $480\ \mathrm{K}$ reservoir each cycle. Determine the greatest possible work delivered to the work store per cycle, consistent with the second law, and state whether the limiting cycle is reversible or irreversible.

[4]

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