175. The electron in the hydrogen atom is in the ground state. The energy required for the electron to jump from the ground state to the first excited state is how many joules?
$$(e = 1.6\times10^{-19}\ \text{C},\quad E_R = 13.6\ \text{eV})$$

(1) $1.632\times10^{-18}$

(2) $3.176\times10^{-18}$

(3) $4.72\times10^{-19}$

(4) $5.44\times10^{-19}$

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176. A scientist refers to an old charcoal sample and claims that the age of this charcoal is about 22920 years. To confirm this claim, carbon-14 in this charcoal: what percentage of the normal amount of carbon-14 present in fresh charcoal must have been newly produced? (Half-life of carbon-14 is 5730 years.)
(1) $1.56$ (2) $3.13$ (3) $6.25$ (4) $12.5$

177. Two point electric charges $q_1 = 20\,\mu\text{C}$ and $q_2 = -5\,\mu\text{C}$ are fixed at a distance of 30 cm from each other. The electric charge $q_2 = 15\,\mu\text{C}$ is placed at a point in this medium such that the net electric force on it is zero.
In this situation, how many newtons is the electric force exerted on $q_2$? $\left(k = 9\times10^9\,\dfrac{\text{N}\cdot\text{m}^2}{\text{C}^2}\right)$
(1) $1.5$ (2) $2.5$ (3) $3$ (4) $5$

178. In the figure below, the net electric field at point A is zero. $\left|\dfrac{q_2}{q_1}\right|$ is equal to?
[Figure: Three charges $q_2$, $q_3$, and $q_1$ arranged at corners of a square, with point A at the bottom-left corner.]
\begin{flushright} (1) $2$
(2) $2\sqrt{2}$
(3) $4$
(4) $4\sqrt{2}$ \end{flushright}

179. Two small conducting spheres with equal and opposite electric charges, $q_1 > 0$ and $|q_2| > q_1$, are held at a fixed distance and an electric force $F$ is exerted on them. If we bring the two spheres into contact and then place them at the same distance, the electric force exerted on them decreases by 20\%. $\left|\dfrac{q_2}{q_1}\right|$ is equal to?
(1) $2$ (2) $4$ (3) $5$ (4) $10$

180. Two identical metal spheres A and B with radii 5 cm having electric charges $q_A = 20\,\mu\text{C}$ and $q_B = -4\,\mu\text{C}$ are brought into contact and then separated. How many microcoulombs does the surface charge density of sphere A decrease per square meter? $(\pi = 3)$
(1) $150$ (2) $300$ (3) $400$ (4) $800$

181. The instrument shown below is used to measure length. What is the name of this instrument and what is its measurement error?
[Figure: Image of a micrometer reading 20083]

1. [(1)] Micrometer and $0.001\,\text{mm}$
2. [(2)] Caliper and $0.001\,\text{mm}$
3. [(3)] Micrometer and $0.003\,\text{mm}$
4. [(4)] Caliper and $0.003\,\text{mm}$

182. A capacitor with capacitance $5\,\mu\text{F}$ has charge $q$. If its electric charge of $3\,\text{mC}$ is separated from the negative plate and transferred to the positive plate, the stored energy increases by $4.5\,\text{J}$. How many millicoulombs is $q$?
(1) $3$ (2) $6$ (3) $9$ (4) $12$
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183. In the circuit below, the potential difference across battery $\varepsilon_2$ is $3/5$ volts. The power consumed by resistance $R$ is how many watts?
[Figure: Two batteries in series branches: left branch has $1\Omega$ internal resistance and $\varepsilon_2 = 3\text{V}$, right branch has $1\Omega$ internal resistance and $\varepsilon_1 = 8\text{V}$, connected to resistors $R$ and $4R$ in series]

• [(1)] $1.6$
• [(2)] $2.5$
• [(3)] $3.2$
• [(4)] $1.5$

184. In the circuit below, the voltmeters are ideal and both lamps are on. If switch $k_1$ is opened, which of the voltmeters will read zero?
[Figure: Circuit with battery $\varepsilon$, two branches each containing a switch $k_1$ or $k_2$, lamps $L_1$ and $L_2$, and voltmeters $V_1$, $V_2$, and $V$]

• [(1)] $V_1$
• [(2)] $V_2$
• [(3)] $V_1$ and $V$
• [(4)] $V_2$ and $V$

185. The circuit below shows an electrical circuit. If the power consumed by resistance $R_2$ is 6 times the power consumed by resistance $R_3$, and $R_1 = 6\,\Omega$, how large is $R_2$?
[Figure: Circuit with current $I$, resistors $R_1 = 6\,\Omega$ in series, $R_2$ in parallel with $R_3 = 12\,\Omega$]

• [(1)] $18$
• [(2)] $12$
• [(3)] $8$
• [(4)] $6$

186. In the circuit below, if the variable resistance increases from zero to $18\,\Omega$, the terminal voltage of the battery changes from how many volts to how many volts?
[Figure: Circuit with variable resistor $R$, fixed resistor $6\,\Omega$, battery with internal resistance $r = 1.5\,\Omega$ and $\varepsilon = 12\,\text{V}$]

• [(1)] 12 to 6
• [(2)] 12 to 9
• [(3)] zero to 6
• [(4)] zero to 9

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187. In a uniform magnetic field, a particle with charge $\alpha$ moves perpendicular to the magnetic field with velocity $v = 5 \times \frac{\text{m}}{\text{s}}$, and the acceleration resulting from the magnetic force is $4 \times 10^5 \, \frac{\text{m}}{\text{s}^2}$. How many gauss is the magnitude of the magnetic field?
$$\left(\text{mass of particle } \alpha = 6.68 \times 10^{-27} \, \text{kg} \text{ and } e = 1.6 \times 10^{-19} \, \text{C}\right)$$
(1) $1.67$ (2) $2.78$ (3) $3.34$ (4) $4.05$

188. In the figure below, two parallel and long wires carry electric currents passing through them. If the magnetic field at point $A$ is zero, which statement is correct?
\begin{minipage}{0.35\textwidth} [Figure: Two parallel wires labeled (1) carrying current $I_1$ to the right, and (2) carrying current $I_2$ to the right, with point A between them.] \end{minipage} \begin{minipage}{0.6\textwidth} (1) $I_2$ is in the opposite direction to $I_1$ and smaller than it.
(2) $I_2$ is in the opposite direction to $I_1$ and larger than it.
(3) $I_2$ is in the same direction as $I_1$ and larger than it.
(4) $I_2$ is in the same direction as $I_1$ and smaller than it. \end{minipage}

189. According to the figure below, a uniform electric field and a magnetic field are perpendicular to each other in a medium, and a positively charged particle moves in that space with velocity $\vec{V}$. In which direction should it move so that the net force on it is zero? (Neglect the weight of the particle.)
[Figure: Diagram showing directions A (up), B (right), C (down), D (left), with electric field $\vec{E}$ pointing out of the page, magnetic field $\vec{B}$ pointing left, and velocity vectors $\vec{v}$ shown in multiple directions.]
(1) $A$ (2) $B$ (3) $C$ (4) $D$

190. In the figure below, at the moment the switch is closed, what is the direction of the induced current, and when the switch is closed and the rheostat resistance is gradually decreased, what is the direction of the induced current?
[Figure: Circuit with a rheostat (resistor), a galvanometer, a switch, and a battery. The galvanometer coil is shown with current direction indicators (1) and (2).]
(1) (1) and (1) (2) (1) and (2) (3) (2) and (1) (4) (2) and (2)
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191. The length of solenoid A is twice the length of solenoid B, and the number of turns of solenoid A is also twice the number of turns of solenoid B. If the electric current passing through them is equal, the energy stored in solenoid A compared to solenoid B is how many times, and the magnetic field inside solenoid A compared to the magnetic field inside solenoid B is how many times? (The solenoids have no iron core and their cross-sectional area and wire diameter are equal.)
(1) 1 and 1 (2) 2 and 1 (3) 2 and 2 (4) 4 and 2

192. An airplane with a mass of $60$ tons moves at a speed of $80\,\dfrac{\text{m}}{\text{s}}$ and takes off from the runway, rising to an altitude of $600$ meters above the ground in one minute. During this one minute, the work done by the weight force on the airplane is how many joules, and the kinetic energy of the airplane increases by how many joules? $\left(g = 10\,\dfrac{\text{N}}{\text{kg}}\right)$
(1) $3.6\times10^8$ and $9.36\times10^8$ (2) $-3.6\times10^8$ and $2.16\times10^8$ [6pt] (3) $3.6\times10^8$ and $2.16\times10^8$ (4) $-3.6\times10^8$ and $9.36\times10^8$

193. In the figure below, two liquids are in equilibrium. If $\rho_1 = 1.2\,\dfrac{\text{g}}{\text{cm}^3}$ and $\rho_2 = 1\,\dfrac{\text{g}}{\text{cm}^3}$, the gauge pressure of the enclosed gas is how many Pascals? $\left(g = 10\,\dfrac{\text{N}}{\text{kg}}\right)$
[Figure: A U-shaped tube with gas trapped on the left side; the left column shows 90 cm height of gas above liquid $\rho_2$, and the right side shows 45 cm of liquid $\rho_1$ at the bottom.]
(1) 3000
(2) 3600
(3) 5000
(4) 5800

194. If at a depth of 5 cm in a liquid the pressure is 100 kilopascals, and at a depth of 20 cm the pressure is 106 kilopascals, then the air pressure in the environment is how many kilopascals? $\left(g = 10\,\dfrac{\text{m}}{\text{s}^2}\right)$
(1) 96 (2) 97 (3) 98 (4) 99

195. 20 grams of ice is at $0^\circ$C (melting point). How many joules of heat are needed to melt it and raise the temperature of the resulting water to $50^\circ$C? $\left(L_f = 336\,\dfrac{\text{J}}{\text{g}},\; c_{\text{water}} = 4.2\,\dfrac{\text{J}}{\text{g}\cdot{}^\circ\text{C}}\right)$
(1) 10920 (2) 9050 (3) 8190 (4) 7560
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196- A copper rod of length $50\,\text{cm}$ and cross-sectional area $5\,\text{cm}^2$. One end of this rod is at a constant temperature of $80^\circ\text{C}$ and the other end is at $30^\circ\text{C}$ and is insulated and connected to a block. Under steady-state conditions, the rate of heat flow through the rod is harmonious. How many joules per second and how many degrees Celsius is the temperature of the end block?
$$\left(k = 400\,\frac{\text{W}}{\text{m.K}}\right)$$
(1) $40$ and $20$ (2) $70$ and $30$ (3) $40$ and $50$ (4) $70$ and $50$

197- A Carnot refrigerator operates between temperatures $27^\circ\text{C}$ and $127^\circ\text{C}$ and does $127\,\text{J}$ of work. What is its coefficient of performance?
(1) $\dfrac{4}{3}$ (2) $\dfrac{5}{3}$ (3) $3$ (4) $4$

198- According to the figure below, for a fixed amount of ideal gas, in a process going from $V_1$ to $V_2$, which of the following statements is correct?
[Figure: P-V diagram showing a curve from point B to point A, with $V_2$ and $V_1$ on the horizontal axis]

• [a-] The internal energy of the gas increases.
• [b-] The temperature of the gas decreases.
• [p-] The temperature of the gas remains constant.
• [t-] The work done on the gas equals the heat absorbed by the gas.
• [th-] The work done on the gas equals the change in internal energy of the gas.

(1) a and th (2) a and t (3) b and th (4) p and t

199- The isobaric pressure of an ideal gas is $5\times10^4\,\text{Pa}$ and its internal energy is $600\,\text{J}$. If we double the volume of the gas and also double the internal energy of the gas, how many joules will the internal energy of the gas be?
$$(P_\circ = 10^5\,\text{Pa})$$
(1) $800$ (2) $1250$ (3) $1600$ (4) $2400$