173- In the figure shown, two conducting rods are placed between two heat sources. If the cross-sectional area of rod A is $\frac{1}{2}$ the cross-sectional area of rod B, and the thermal conductivity of rod A is 6 times the thermal conductivity of rod B, what is the ratio of the thermal conduction rate in rod A to the thermal conduction rate in rod B?
\begin{minipage}{0.45\textwidth} [Figure: Two rods A and B connected between heat sources $T_1$ and $T_r \neq T_1$] \end{minipage} \begin{minipage}{0.45\textwidth}

• [(1)] $2$
• [(2)] $4(2)$
• [(3)] $\dfrac{1}{2}$
• [(4)] $\dfrac{1}{4}$

\end{minipage}
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174- In the figure below, two cylindrical containers have equal base diameters. If we open the valve connecting the two containers, how many centimeters will the water level rise? (density of oil $= 800\,\dfrac{\text{kg}}{\text{m}^3}$ and density of water $= 1000\,\dfrac{\text{kg}}{\text{m}^3}$)
[Figure: Two connected cylindrical containers, each with base diameter $50\,\text{cm}$; left container has water (height $50\,\text{cm}$), right container has oil (height $50\,\text{cm}$), connected at the bottom by a valve.]

• [(1)] 10
• [(2)] 5
• [(3)] 4
• [(4)] 2.5

175- Two liquids A and B with densities $\rho_A = 1.2\,\dfrac{\text{g}}{\text{cm}^3}$ and $\rho_B = 0.6\,\dfrac{\text{g}}{\text{cm}^3}$ are mixed together and poured into a cylindrical container. If we assume the volume of the mixture of liquid A equals $\dfrac{1}{2}$ the volume of liquid B, and the height of the mixture in the container is 75 cm, the pressure exerted from the bottom of the container on the floor of the mixed liquid is how many pascals? $\left(g = 10\,\dfrac{\text{m}}{\text{s}^2}\right)$

• [(1)] 6000
• [(2)] 6750
• [(3)] 9000
• [(4)] 9750

176- The mass of an empty metal container is 300 grams. If we fill this container with a liquid of density $1.2\,\dfrac{\text{g}}{\text{cm}^3}$, the total mass becomes 540 grams, and if we fill it with a type of oil, the total mass becomes 460 grams. The density of this oil is how many grams per liter?

• [(1)] 950
• [(2)] 900
• [(3)] 850
• [(4)] 800

177- How many electrons must be removed from a metal coin so that its electric charge becomes $+1\,\mu\text{C}$? $(e = 1.6 \times 10^{-19}\,\text{C})$

• [(1)] $1.6 \times 10^{6}$
• [(2)] $1.6 \times 10^{12}$
• [(3)] $6.25 \times 10^{6}$
• [(4)] $6.25 \times 10^{12}$

178- In the figure below, two charged electric strings are parallel and of equal length, and are in equilibrium. The tension $T_1$ is how many times the tension $T_2$?
[Figure: Two charged strings hanging from a ceiling, making angles $60°$ and $30°$ with the vertical, with tensions $T_1$ and $T_2$ and charges $q$ at their ends.]

• [(1)] $\dfrac{1}{2}$
• [(2)] $\dfrac{\sqrt{3}}{2}$
• [(3)] $\sqrt{3}$
• [(4)] 2

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179- Between two parallel plates that are $2\,\text{cm}$ apart, we have created an electric potential difference of $500\,\text{V}$. If an alpha particle is placed between these two plates, how many newtons of electric force will act on it?
$(e = 1.6 \times 10^{-19}\,\text{C})$
(1) $8 \times 10^{-15}$ (2) $8 \times 10^{-15}$ (3) $4 \times 10^{-15}$ (4) $4 \times 10^{-15}$

180- In the circuit shown, how many microjoules of energy is stored in the capacitor?
[Figure: Circuit with EMF source $\varepsilon = 10\,\text{V}$, internal resistance $r = 0$, resistors $R_1 = 1\,\Omega$, $R_2 = 8\,\Omega$, $R_3 = 2\,\Omega$, $R_4 = 2\,\Omega$, and capacitor $C = 5\,\mu\text{F}$]
(1) zero (2) 10 (3) 40 (4) 90

181- In the circuit shown, what is the input power to the battery of the main branch, in watts?
[Figure: Circuit with $\varepsilon_1 = 6\,\text{V}$, $r_1 = 1\,\Omega$, $\varepsilon_2 = 12\,\text{V}$, $r_2 = 2\,\Omega$, $r_3 = 2\,\Omega$, two resistors of $2\,\Omega$ and $2\,\Omega$, and $I_1 = \frac{1}{2}\,\text{A}$]
(1) $7.5$ (2) $6$ (3) $3$ (4) $2.5$

182- In the circuit below, by increasing resistance $R_2$, how do the current indicated by ammeter A and the potential difference indicated by voltmeter V change? (in order, from right to left)
[Figure: Circuit with EMF source $\varepsilon$, internal resistance $r$, resistors $R_1$, $R_2$, $R_3$, voltmeter V, and ammeter A]
(1) decrease --- decrease
(2) decrease --- increase
(3) increase --- increase
(4) increase --- decrease

183- Two long parallel wires are $20\,\text{cm}$ apart and carry electric currents of $10\,\text{A}$ and $5\,\text{A}$ in opposite directions. The wires repel each other and the repulsive force exerted on each wire per one meter of the other wire is how many newtons, and what is the direction of the currents relative to each other?
$$\left(\mu_0 = 4\pi \times 10^{-7}\,\frac{\text{T}\cdot\text{m}}{\text{A}}\right)$$
(1) $5 \times 10^{-5}$ and in the same direction (2) $5 \times 10^{-7}$ and in the same direction
(3) $5 \times 10^{-5}$ and in opposite directions (4) $5 \times 10^{-7}$ and in opposite directions
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184- A proton moves at an angle of $90°$ with respect to a magnetic field of magnitude $2\circ \text{ m T}$ and a magnetic force of $1.28\times10^{-16}$ N is exerted on it. What is the kinetic energy of the proton in electron volts?
$(m_p = 1.7\times10^{-27}\ \text{kg}\ \text{ and }\ e = 1.6\times10^{-19}\ \text{C})$
(1) $2.5$ (2) $5$ (3) $8.5$ (4) $17$

185- The length of a coreless solenoid is $50\ \text{cm}$ and the area of each turn is $10\ \text{cm}^2$. This solenoid has $2000$ turns close together and a current of $0.5\ \text{A}$ passes through it. What is the self-inductance coefficient of the solenoid in SI?
$$\left(\mu_\circ = 12.5\times10^{-7}\ \frac{\text{T.m}}{\text{A}}\right)$$
(1) $0.01$ (2) $0.05$ (3) $0.10$ (4) $0.50$

186- The self-inductance coefficient of a solenoid is $2\ \text{H}$ and a current of $0.4\ \text{A}$ passes through it. With which condition does a self-induced EMF of $6\ \text{V}$ get produced in the solenoid?

1. [(1)] The electrical resistance across it is $15\ \Omega$.
2. [(2)] The electrical current changes at a rate of $\frac{\text{A}}{\text{s}}$ with a rate of $15\ \frac{\text{A}}{\text{s}}$.
3. [(3)] The electrical resistance across it is $3\ \Omega$.
4. [(4)] The electrical current changes at a rate of $3\ \frac{\text{A}}{\text{s}}$.

187- An object of mass $0.5\ \text{kg}$ is attached to a light spring with constant $200\ \frac{\text{N}}{\text{m}}$, placed on a horizontal frictionless surface and oscillates. If the amplitude is $5\ \text{cm}$, what is the speed of the oscillation center in meters per second?
(1) $0.8$ (2) $1.6$ (3) $2.4$ (4) $3.6$

188- The velocity–time graph of a spring–mass oscillator is shown below. According to the graph, how many seconds after $t = 0$ does the magnitude of the oscillator's acceleration first become $4\pi^2\ \frac{\text{cm}}{\text{s}^2}$?
[Figure: Velocity (cm/s) vs time (s) graph showing a sinusoidal curve with amplitude $2\pi$ and period approximately 2 s; the curve starts at 0, reaches $+2\pi$ then $-2\pi$]
(1) $\dfrac{1}{2}$ (2) $\dfrac{1}{6}$ (3) $\dfrac{1}{9}$ (4) $\dfrac{1}{12}$
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189. Two coherent wave sources $S_1$ and $S_2$, in a homogeneous medium, emit waves and the wavelength is $25\,\text{cm}$. In this medium, the distance between the two sources $M$ from these two sources is $50\,\text{cm}$ and $80\,\text{cm}$ respectively. The phase difference between the two waves reaching point $M$ simultaneously, and the superposition of the two waves at this point, is:

• [(1)] $3\pi$, constructive (2) $3\pi$, destructive (3) $\dfrac{3\pi}{2}$, constructive (4) $\dfrac{3\pi}{2}$, destructive

190. The transverse wave function in a wire whose cross-sectional diameter is $2\,\text{mm}$ and its density is $A\,\dfrac{\text{g}}{\text{cm}^3}$ is, in SI units: $$u_y = 0.02\sin(3t - 1.5x)$$ How many newtons is the tension in the wire? $(\pi = 3)$

• [(1)] $4.8$ (2) $96$ (3) $9.6$ (4) $48$

191. The figure below shows a transverse wave on a string. Which of the following statements about points $M$ and $N$ on the string is correct?
[Figure: A transverse wave on a string with $u_y$ axis vertical and $x$ axis horizontal; points M and N are marked on the string, with velocity vector $V$ shown at one point.]

• [(1)] Their speeds are equal at every moment.
• [(2)] They have equal amplitudes and frequencies.
• [(3)] They are in opposite phase.
• [(4)] They are in phase.

192. If we multiply the amplitude of a sound source by 4, for a certain listening point, the sound intensity level increases by $1/3$. In this case, the sound intensity level for that listener reaches how many decibels? $(\log 2 = 0.3)$

• [(1)] $12$ (2) $32$ (3) $50$ (4) $52$

193. The figure below shows a pipe that produces sound with wavelength $\lambda_1$ and is resonating. If sound with wavelength $\lambda_2$ can also resonate in the same pipe, the ratio $\dfrac{\lambda_2}{\lambda_1}$ can be which of the following?
[Figure: A closed pipe diagram showing standing wave resonance.]

• [(1)] $\dfrac{2}{5}$ (2) $\dfrac{3}{7}$ (3) $\dfrac{2}{3}$ (4) $\dfrac{3}{4}$

194. A sound source moving with speed $\dfrac{1}{n}$ of the speed of sound approaches a stationary listener, and continues along the same path at the same speed. If in the first case the frequency heard by the listener is $\Delta f$ and in the second case the frequency of the source decreases, and the frequency heard by the listener is $\Delta f'$, the ratio $\dfrac{\Delta f}{\Delta f'}$ is:

• [(1)] $1$ (2) $\dfrac{n-1}{n}$ (3) $\dfrac{n+1}{n-1}$ (4) $\dfrac{1}{n+1}$

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195. What is the common feature in the propagation of electromagnetic waves?
(1) Speed of propagation in vacuum and the governing laws on them (2) Nature and speed of propagation in transparent media
(3) Method of production and governing laws on them (4) Nature and method of manifestation

196. In a Young's double-slit experiment, the path difference of light from the third dark fringe from the center is 1500 nanometers. In this experiment, the path difference of light from the second bright fringe is how many nanometers?
\[ \text{(1)}\ 800 \qquad \text{(2)}\ 1200 \qquad \text{(3)}\ 1600 \qquad \text{(4)}\ 1800 \]

197. In the hydrogen atom, the electric potential energy of the electron in the electric field of the nucleus is equal to which of the following? ($r$ is the radius of the electron's orbit and $k$ is Coulomb's constant.)
\[ \text{(1)}\ \frac{ke^2}{2r} \qquad \text{(2)}\ -\frac{ke^2}{2r} \qquad \text{(3)}\ \frac{ke^2}{r} \qquad \text{(4)}\ -\frac{ke^2}{r} \]