183- In the circuit below, when the sliding rheostat moves from point A to point B, how do the power consumed by resistance $R_1$ and the output power of the generator change, respectively?
[Figure: Circuit with sliding rheostat between points A and B, resistance $R_1$ in parallel, and a battery with internal resistance $r = 2\,\Omega$ and EMF $\varepsilon$, with $R_2 = 6\,\Omega$]

• [(1)] Decrease -- Increase
• [(2)] Decrease -- Decrease
• [(3)] Increase -- Decrease
• [(4)] Increase -- Increase

184- A bar magnet is placed on a table as shown in the figure below. A magnetic monopole that can rotate freely around a vertical axis is placed near the magnet. The monopole moves in a circular path around the magnet. How many degrees does the magnet rotate along this circular path in one revolution?
[Figure: Bar magnet with N and S poles, and a magnetic monopole moving in a circular path around it]

• [(1)] $180°$
• [(2)] $270°$
• [(3)] $360°$
• [(4)] $720°$

185- Using a wire of length $100$ m, we form a circular loop of radius $R$. How many centimeters should $R$ be so that if current $I = 10\,\text{A}$ passes through the loop, the magnetic field at its center is $T = 2.5 \times 10^{-2}\,\text{T}$?
$$\left(\mu_\circ = 4\pi \times 10^{-7}\,\frac{\text{T.m}}{\text{A}}\right)$$

• [(1)] $20$
• [(2)] $20\sqrt{2}$
• [(3)] $40$
• [(4)] $40\sqrt{2}$

186- At a power plant, the voltage is $10000$ V, which is converted by transformer A to $400000$ V and then transmitted to a city. In the city, transformer B converts the voltage to $5000$ V. If the ratio of the number of turns in the primary to secondary coil in transformer A is $K_A$, and in transformer B is $K_B$, then $\dfrac{K_A}{K_B}$ equals?

• [(1)] $20$
• [(2)] $80$
• [(3)] $1200$
• [(4)] $3200$

Calculation Space
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187. A rectangular coil with a fixed period rotates inside a uniform magnetic field at constant speed. The magnetic field lines are perpendicular to the coil surface. Which of the following graphs correctly shows the variation of magnetic flux and induced EMF versus time in one period? (The dashed graph corresponds to the change in magnetic flux.)
[Figure: Four graphs labeled (1), (2), (3), (4) showing $\phi$ and $\varepsilon$ versus $t$ over period $T$, with solid and dashed sinusoidal curves phase-shifted relative to each other.]

188. A pendulum oscillates along the line $MN$ with length $6\,\text{cm}$. If the time it takes to travel from $M'$ to $N'$ is $\frac{1}{2}$ seconds, what is the speed (in cm/s) of the pendulum when passing through point $N'$?
[Figure: A horizontal line with points M, M$'$, O, N$'$, N marked, and $MM' = N'N = 1.5\,\text{cm}$]

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

189. The equation of position of a simple harmonic oscillator in SI units is $x = \circ + \dfrac{\pi^2}{\mathbf{f}}\,\mathbf{a}$ at $t = \dfrac{1}{\mathbf{r}}\,\text{s}$. At this moment, the kinetic energy of the oscillator is how many times its total mechanical energy? (The oscillator passes through $x = \circ$ at $t = \circ$.)
$$\frac{1}{\mathbf{f}} \quad (4) \qquad \frac{1}{\mathbf{r}} \quad (3) \qquad \frac{\mathbf{r}}{\mathbf{f}} \quad (2) \qquad 1 \quad (1)$$

190. In uniform simple harmonic motion along a straight path, the relationship between velocity and position in SI units is $V^2 = 2500\,Z^2 - 2500\,X^2$. Which of the following quantities is $Z$?

• [(1)] amplitude
• [(2)] damping
• [(3)] acceleration
• [(4)] angular amplitude

\rule{\textwidth}{0.4pt}
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191- A transverse wave with speed $100\,\dfrac{\text{m}}{\text{s}}$ and frequency $50\,\text{Hz}$ is propagating in a medium. The phase change of a point on the medium over a time interval of $2.5$ milliseconds is how many radians?
(1) $\pi$ (2) $\dfrac{\pi}{2}$ (3) $\dfrac{\pi}{4}$ (4) $\dfrac{\pi}{8}$

192- In the figure, a tuning fork is in the process of resonance. If for each unit of weight placed inside the cup, three antinodes of the string are created, which of the following occurs when the weight is gradually increased?
[Figure: A tuning fork connected to a string over a pulley with a hanging mass M]

1. The number of antinodes decreases and the frequency also decreases.
2. The number of antinodes increases and the frequency also increases.
3. The number of antinodes decreases but the frequency remains constant.
4. The number of antinodes increases but the frequency remains constant.

193- The amplitude of oscillations of a sound wave decreases by $20$ percent. At a certain point, the sound intensity level decreases by how many decibels? $(\log 2 = 0.3)$
(1) $1$ (2) $2$ (3) $14$ (4) $20$

194- An ambulance whose siren frequency is $1200\,\text{Hz}$ starts from a bicycle moving at speed $5\,\dfrac{\text{m}}{\text{s}}$ and overtakes it. After the ambulance passes the bicycle, the cyclist receives a frequency of $1150\,\text{Hz}$ from the ambulance. The speed of the ambulance is how many meters per second? $\left(V = 340\,\dfrac{\text{m}}{\text{s}}\right)$
(1) $10$ (2) $20$ (3) $30$ (4) $40$

195- According to the figure below, two radio stations A and B are located $80\,\text{km}$ apart and each sends a signal. Point P is located $60\,\text{km}$ from A. These two signals reach point P with what time difference? $\left(c = 3\times10^{8}\,\dfrac{\text{m}}{\text{s}}\right)$
[Figure: Point P above, points A and B on a horizontal line, with P located 60 km from A and A and B separated by 80 km]
(1) $\dfrac{4}{3}\times10^{-4}$ (2) $\dfrac{4}{3}\times10^{-7}$ (3) $\dfrac{2}{3}\times10^{-4}$ (4) $\dfrac{2}{3}\times10^{-7}$

196- In Young's experiment, the slit separation is $D$ and point P on the screen is the location of the third bright fringe. If the slit separation increases to $\dfrac{D}{5}$, point P becomes the location of which fringe?
(1) fourth bright (2) fourth dark (3) third dark (4) third bright
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197. In a photoelectric experiment, the graph shows the kinetic energy changes of the fastest photoelectrons emitted from two metals A and B as a function of incident light frequency. According to the graph, the threshold frequencies of metals A and B are $f_A$ and $f_B$ respectively, and the maximum speeds of photoelectrons emitted from these two metals are equal. If $\dfrac{f_B}{f_A} = n$, which answer is correct?
[Figure: Graph of $K_{\max}$ vs. $f(10^{15}\ \text{Hz})$ showing two lines A and B with x-intercepts at approximately 0.5 and 1]
\begin{flushright} (1) $1 < n < 2$
(2) $n = 1$
(3) $n = \dfrac{1}{2}$
(4) $\dfrac{1}{2} < n < 1$ \end{flushright}

198. In a hydrogen atom, an electron transitions from level $n$ to level $n'$ and emits light with frequency $562.5\ \text{THz}$. $n$ and $n'$ are respectively which values? $$\left(c = 3\times10^{8}\ \frac{\text{m}}{\text{s}},\ R_H = 0.01\ \text{nm}^{-1}\right)$$
(1) 2 and 1 (2) 3 and 1 (3) 4 and 2 (4) 5 and 3

199. Initially, the number of radioactive nuclei of elements A and B are equal. After time $\Delta t$, the remaining nuclei of element A are four times the remaining nuclei of element B. If the half-life of element B is equal to the half-life of element A, and $n_A$ and $n_B$ are the number of remaining nuclei of A and B after time $\Delta t$, which of the following is correct?
(1) $n_A - n_B = 4$ (2) $n_B - n_A = 4$ (3) $n_A - n_B = 2$ (4) $n_B - n_A = 2$

200. In the band structure of a solid, the conduction band is full of electrons and the valence band is also full. What is emitted from it?
\begin{tabbing} \=(1) resonance electrons -- resonance light \=(2) valence electrons -- resonance light \>(3) resonance electrons -- valence light \>(4) valence electrons -- valence light \end{tabbing}
Calculation Space
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201- Which statement is correct?

1. Most isotopes of known elements are unstable.
2. In the ion ${}^{+}\text{Li}^{Y}$, the number of electrons equals the number of neutrons.
3. Chlorine atoms are mostly formed by their heavier isotopes.
4. If the atomic mass of element ${}^{Y}\text{C}$ is $2.33$ times the atomic mass of ${}^{1}\text{H}$, its atomic mass is $16\,\text{amu}$.

202- Materials that have the property of fluorescence absorb light of wavelength .................. and emit it as light of wavelength .................. and are released. The light continues after the light source is cut off.

1. Definite, continues for a long time after the source is cut off.
2. Short, colorless, cut off.
3. Long, continues for a long time after the source is cut off.
4. Definite, long, colorless, cut off.

203- Noble gases in which group of the periodic table are located, what are the atomic numbers of the first and third period noble gases? (Read the options from right to left.)
(1) $16,17$ (2) $18,17$ (3) $17,18$ (4) $18,16$

204- An element whose last electronic subshell configuration is $4s^2\,4p^3\,4s^2$ is in which group and which period of the periodic table?
(1) 13, fourth (2) 13, fifth (3) 15, fourth (4) 15, third

205- Which statement about the periodic table of elements is correct?

1. The last element of each period in group 10 has a place.
2. Elements of groups 14 to 18 are called ordinary elements under normal conditions.
3. The last subshell of intermediate elements contains 2 electrons.
4. In elements of group 17, electronegativity and reactivity decrease with increasing atomic number.

206- The number of oxygen atoms in the chemical formula of which two compounds is equal?
(1) Stannic oxide, hydrogen peroxide (2) Potassium permanganate, magnesium sulfate
(3) Copper(II) sulfate, iron(III) nitrite (4) Ammonium nitrate, calcium hydrogen carbonate

207- How many of the following statements are correct?

• Carbon dioxide also says carbon(II) oxide.
• The oxidation number of phosphorus atom in phosphorus pentabromide is $+5$.
• The difference in oxidation number of nitrogen atom in ions $\text{NH}_4^+$ and $\overline{\text{NO}_2}$ is $2$.
• The oxidation number of some elements can be used in naming some molecular compounds.
• The oxidation number of each atom is the apparent electrical charge assigned to it in the compound.

(1) $1$ (2) $2$ (3) $3$ (4) $4$
[Space for calculations]
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