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Physics QUESTION #5588

When a potential difference of 5 V is applied across a wire of length 0.1 m, the drift speed of electrons is $2.5 \times 10^{-4}\,\text{m/s}$. If the electron number density in the wire is $8 \times 10^{28}\,\text{m}^{-3}$, the resistivity of the material is closest to:

$1.6 \times 10^{-8}\,\Omega\text{m}$
$1.6 \times 10^{-7}\,\Omega\text{m}$
$1.6 \times 10^{-6}\,\Omega\text{m}$
$1.6 \times 10^{-5}\,\Omega\text{m}$✔️

Correct Answer Logic:

Electric field: $E = \frac{V}{L} = \frac{5}{0.1} = 50\,\text{V/m}$

Current density: $J = nev_d = 8 \times 10^{28} \times 1.6 \times 10^{-19} \times 2.5 \times 10^{-4} = 3.2 \times 10^{6}\,\text{A/m}^2$

Resistivity: $\rho = \frac{E}{J} = \frac{50}{3.2 \times 10^{6}} \approx 1.56 \times 10^{-5}\,\Omega\text{m}$

Closest option: $1.6 \times 10^{-5}\,\Omega\text{m}$. Answer: D.

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Chemistry QUESTION #7402

Question 2

Which of the following oxides is NOT expected to react with sodium hydroxide?

BeO
$\text{B}_2\text{O}_3$
CaO✔️
$\text{SiO}_2$

Correct Answer Logic:

Reaction with NaOH (basic): Only acidic or amphoteric oxides react with NaOH.

BeO: amphoteric → reacts with NaOH
B₂O₃: acidic → reacts with NaOH
CaO: basic → does NOT react with NaOH (two bases don't react)
SiO₂: acidic → reacts with NaOH → Na₂SiO₃

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Civil Procedure QUESTION #3739

Question 3

During a trial, a lawyer wants to show a witness a document to help them remember a detail they have forgotten. After looking at the document, the witness says, 'Oh yes, I remember now.' The lawyer then tries to introduce the document itself into evidence. Is the document admissible?

Yes, as 'Past Recollection Recorded.'
No, under 'Refreshing Recollection,' the document itself is not usually admissible as evidence by the party using it to refresh.✔️
Yes, because the witness authenticated it.
No, unless it's a 'Business Record.'

Correct Answer Logic:

Under Rule 612 (Refreshing Recollection), the adverse party can have the writing produced and introduced, but the party using it to refresh the witness's memory generally cannot introduce it as an exhibit (unless it meets another exception like 803(5)).

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Constitutional Law QUESTION #5822

Question 4

Congress passes a law providing that 'no federal court shall have jurisdiction to hear any case involving the constitutionality of the Selective Service Act.' Is this law valid?

Yes, because Article III gives Congress power to make 'exceptions and regulations' to the Supreme Court's appellate jurisdiction.✔️
Yes, because military matters are 'political questions' beyond judicial review.
No, because Congress cannot strip the Supreme Court of all jurisdiction over a federal constitutional issue.
No, because it violates the Separation of Powers by dictating the outcome of cases.

Correct Answer Logic:

Under Article III, Section 2, Congress has the power to regulate and limit the appellate jurisdiction of the Supreme Court and to define the jurisdiction of inferior federal courts. While there are limits (it can't destroy the 'essential role' of the court), the MBE generally recognizes this broad 'Exceptions Clause' power.

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Boilers Mechanical Engineering QUESTION #2442

Question 5

Resonance in a forced vibration system occurs when:

The forcing frequency is less than $\omega_n / 2$
The forcing frequency $p$ equals the natural frequency $\omega_n$: $p = \omega_n$✔️
The damping ratio exceeds 0.5
The amplitude is less than the static deflection

Correct Answer Logic:

Resonance occurs when the excitation frequency $p$ equals the natural frequency $\omega_n$. For an undamped system, the amplitude theoretically becomes infinite at resonance.

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General Knowledge QUESTION #8622

Question 6

While the olive branch symbolizes peace, what does the lotus flower symbolize?

Progress
Culture and Civilization✔️
Justice
Romantic love

Correct Answer Logic:

The lotus symbolizes culture and civilization in many traditions.

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The Constitution of Pakistan QUESTION #9341

Question 7

A resolution for a vote of no-confidence against the Prime Minister must be moved by how many members, and must be voted on within what timeframe?

One-third of total membership; within three to ten days
Not less than twenty percent of total membership; not before three days and not later than seven days✔️
Not less than one-fourth of total membership; within five days
A majority of total membership; within forty-eight hours

Correct Answer Logic:

Article 95(1) requires at least 20% of total membership to move the resolution. Article 95(2) mandates the vote cannot be held before three days, nor later than seven days, from the day the resolution is moved — preventing both rushed removal and indefinite delay.

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Dairy Food Science and Technology QUESTION #6000

Question 8

The $Z$-value in thermal processing refers to:

The decimal reduction time at a given temperature
The temperature change required to produce a $10$-fold ($1$ log cycle) change in $D$-value✔️
The total number of logs of microbial reduction achieved
The activation energy of the spoilage reaction

Correct Answer Logic:

$Z$-value is the temperature increase ($^{\circ}\text{C}$ or $^{\circ}\text{F}$) required to reduce the $D$-value by a factor of $10$ (1 log cycle). For $C.\;botulinum$ spores, $z = 10^{\circ}\text{C}$ ($18^{\circ}\text{F}$). $Z$-value is used to calculate equivalent thermal processes: $F_T = D_T \times \log\left(\frac{N_0}{N}\right)$.

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Chemistry QUESTION #7129

Question 9

The combustion of benzene releases $CO_{2}(g)$ and $H_{2}O(l)$. At $25^{\circ}C$, the heat of combustion at constant volume ($\Delta U$) is $-3263.9\text{ kJ mol}^{-1}$. Calculate the heat of combustion at constant pressure ($\Delta H$) in $\text{kJ mol}^{-1}$. ($R = 8.314\text{ J K}^{-1}\text{ mol}^{-1}$)

3260
-3267.6✔️
4152.6
-452.46

Correct Answer Logic:

The relationship is given by $\Delta H = \Delta U + \Delta n_g RT$.
Reaction: $C_{6}H_{6}(l) + 7.5O_{2}(g) \rightarrow 6CO_{2}(g) + 3H_{2}O(l)$.
$\Delta n_g = 6 - 7.5 = -1.5$.
$\Delta H = -3263.9 + (-1.5 \times 8.314 \times 10^{-3} \times 298) = -3263.9 - 3.7 = -3267.6\text{ kJ mol}^{-1}$.

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Paper-I (Anatomy/Physiology and Biochemistry/Microbiology) QUESTION #3507

Question 10

Which oil is a 'Fixed Oil' obtained from animal sources?

Almond oil
Cod Liver Oil✔️
Olive oil
Coconut oil

Correct Answer Logic:

Cod liver oil is a rich source of Vitamin A and D.

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General Knowledge QUESTION #8920

Question 11

Kurchatov is a famous scientist known for his work in:

Nuclear energy✔️
Space technology
Genetics
Electronics

Correct Answer Logic:

Kurchatov was a Soviet nuclear physicist.

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Professional QUESTION #1820

Question 12

Which of the following categories of persons is expressly EXCLUDED from the definition of 'civil servant' under Section 2(b) of the Civil Servants Act 1973?

A member of an All-Pakistan Service
A person holding a civil post connected with defence
A person employed on contract or on work-charged basis✔️
A person holding a permanent post in a civil service of the Federation

Correct Answer Logic:

Section 2(b) provides that a civil servant does not include: (i) a person on deputation from a Province; (ii) a person employed on contract, work-charged basis, or paid from contingencies; or (iii) a worker/workman under the Factories Act 1934 or Workman's Compensation Act 1923. Contract and work-charged employees are explicitly excluded.

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Boilers Mechanical Engineering QUESTION #3979

Question 13

In a 'Fire Tube' boiler, which of the following is true regarding the heat exchange process?

Water circulates inside the tubes, surrounded by hot gases
Hot gases pass through the tubes, surrounded by water✔️
The boiler is only used for very high pressure ($>100~bar$)
There are no tubes used in the design

Correct Answer Logic:

Fire-tube boilers like the Lancashire or Locomotive types have hot gases inside tubes to heat the surrounding water.

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Biomedical Sciences QUESTION #3800

Question 14

What is the physiological effect of parathyroid hormone (PTH) on calcium and phosphate metabolism?

Increased mobilisation of calcium from bone✔️
Decreased renal tubular reabsorption of calcium
Decreased resorption of phosphate from bone
Decreased excretion of phosphate

Correct Answer Logic:

PTH raises serum calcium by stimulating osteoclastic bone resorption, increasing renal tubular calcium reabsorption, and promoting renal phosphate excretion.

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Chemistry QUESTION #7814

Question 15

The efficiency of a chemical reaction is determined by calculating:

Actual yield
Theoretical yield
Percentage yield✔️
Amount of unused reactant

Correct Answer Logic:

Percentage yield = (actual yield/theoretical yield)×100, directly shows reaction efficiency.

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English QUESTION #505

Question 16

MANGLED

Dodged
Grained
Indisputable
Damaged✔️

Correct Answer Logic:

Mangled means severely damaged or mutilated

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Mathematics QUESTION #4090

Question 17

The dimension of the subspace $W$ of all $2\times2$ symmetric matrices (as a subspace of all $2\times2$ matrices) is:

$1$
$2$
$3$✔️
$4$

Correct Answer Logic:

A general $2\times2$ symmetric matrix is $\begin{pmatrix}a&b\\b&c\end{pmatrix}$ with 3 free parameters. A basis for $W$ is $\left\{\begin{pmatrix}1&0\\0&0\end{pmatrix},\begin{pmatrix}0&1\\1&0\end{pmatrix},\begin{pmatrix}0&0\\0&1\end{pmatrix}\right\}$. Hence $\dim(W)=3$.

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