Practice Test 11 - AP Physics 2

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. A laser beam travels in water and strikes a boundary with air at $25^\circ$ to the normal. Water has the higher refractive index ($n_{water} > n_{air}$). Which way does the refracted ray bend as it enters the air?
2. A particle with charge $+2.0\,\mu\text{C}$ moves from point A at $V_A=+30\,\text{V}$ to point B at $V_B=-10\,\text{V}$ in an external electric field. Ignore nonconservative forces. As the charge moves from A to B, the electric potential energy of the charge-field system _____.
3. Two resistors, $R_1=2\ \Omega$ and $R_2=8\ \Omega$, are connected in parallel across an ideal $4\ \text{V}$ source for $6\ \text{s}$. Each has the same voltage $V=4\ \text{V}$, and currents satisfy $I=V/R$. Which resistor dissipates more power?
4. A thin copper plate and a thin glass plate have the same area and thickness. A constant temperature difference is maintained across each. Which conducts more heat per second?
5. A rigid container holds an ideal gas at $T_1=27^\circ\text{C}$ and $P_1=100\ \text{kPa}$. The amount of gas and volume are constant. The gas is warmed to $T_2=127^\circ\text{C}$. Which statement correctly describes the final pressure?
6. A light ray travels in glycerin and reaches a boundary with water at $45^\circ$ to the normal. Glycerin has the higher refractive index ($n_{glycerin} > n_{water}$). Which way does the ray bend as it enters the water?
7. An excited nucleus $^{99}_{43}\text{Tc}^*$ becomes $^{99}_{43}\text{Tc}$ and a photon is detected. Which statement best describes the decay?
8. A fixed source charge $+2Q$ is at the origin. Point A is at $r=0.30\,\text{m}$ and point B is at $r=0.30\,\text{m}$ but in a different direction. A small test charge is placed at each point. Which statement best describes the electric field magnitudes $E_A$ and $E_B$?
9. A closed single-loop circuit contains an ideal $10\,\text{V}$ battery and two identical resistors in series. Which statement best describes the voltage across one resistor?
10. In one closed loop, an ideal battery $\mathcal{E}=10\text{ V}$ is in series with a resistor $R=5\,\Omega$ and a second ideal battery $\mathcal{E}_2=4\text{ V}$. The current $I$ is clockwise. Traverse clockwise: across the $10\text{ V}$ battery from $-$ to $+$ is $+10$, across the $4\text{ V}$ battery from $+$ to $-$ is $-4$, and through $R$ with the current is $-5I$. Which loop equation is correct?
11. Two rods, U and V, are made of different materials but have the same length and area. Their ends are held at $80^\circ\text{C}$ and $20^\circ\text{C}$. Rod U has thermal conductivity $k_U=10\,\text{W/(m\,K)}$ and rod V has $k_V=40\,\text{W/(m\,K)}$. (Conductivity sets heat-flow rate; specific heat affects temperature change when energy is stored.) Which rod has the larger steady heat current?
12. A $-1.0\,\mu\text{C}$ charge moves from A at $V_A=+30\,\text{V}$ to B at $V_B=+90\,\text{V}$. As the charge moves from A to B, the electric potential energy will:
13. At junction $J$, $I_1=0.70\,\text{A}$ leaves to the right and $I_2=0.20\,\text{A}$ leaves upward. Currents $I_3$ enters from the left and $I_4=0.10\,\text{A}$ enters from below (arrows shown). Which current relationship must be true?
14. A small particle with charge $-q$ and mass $m$ is in a circular orbit of radius $R$ around a large, fixed particle with charge $+Q$. What is the minimum speed the small particle must be given to escape to an infinite distance away?
15. In the single closed loop shown, a $12\ \text{V}$ battery (positive terminal encountered first) is in series with $R_1=3.0\ \Omega$ and $R_2=5.0\ \Omega$. Traverse clockwise; take a rise as $+\varepsilon$ across the battery from $-$ to $+$, and a drop as $-IR$ when moving with the current through a resistor. Which equation correctly represents Kirchhoff's loop rule for this loop?
16. A loop contains two resistors, $R_1=4.0\ \Omega$ and $R_2=2.0\ \Omega$, and a $10\ \text{V}$ battery. Traverse clockwise. Use the convention $+\varepsilon$ when moving from $-$ to $+$ through the battery, and $-IR$ when moving with current through a resistor (current is clockwise). Which equation correctly represents the loop?
17. A continuous sinusoidal wave travels at constant speed $v$ in a uniform medium. If the frequency decreases by a factor of 3, which statement correctly describes the wavelength?
18. A student observes that a neon sign emits several sharp spectral lines. The best explanation is that neon atoms have
19. A Bohr-model atom has allowed levels $n=1,2,3$ (forbidden: all energies between levels). Why is the electron in $n=1$ stable?
20. A light ray in a liquid strikes a boundary with air at $10^\circ$ to the normal and refracts into the air. The liquid has the higher refractive index ($n_{liquid} > n_{air}$). Which change best matches the direction of bending at the boundary?

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