Explanation

• The four essential elements of a state are territory, population, government, and sovereignty.
• Sovereignty means the supreme authority to govern without external control.

Additional information:

Examples of sovereign states:

1. Pakistan
2. China
3. United States
4. Saudi Arabia
5. Turkey

Last verified on 13-04-2026

Explanation

• Khewra Salt Mine is the largest and oldest salt mine in Pakistan and the second-largest in the world.
• It is located in Khewra near Pind Dadan Khan, Jhelum District, Punjab.

Additional information:

• It is also called the Mayo Salt Mine.
• The salt deposits were discovered during the campaign of Alexander the Great in 326 BC.
• The mine was officially opened in 1872 during the British period.

Last verified on 14-03-2026

Explanation

• Russia is the largest country in the world by area.
• Total area ≈ 17,098,242 km².
• Covers about 11% of Earth’s land surface.
• Lies in both Europe and Asia (Eurasia).
• Has 11 time zones, the most in the world.
• Population Rank: 9th in the world

Additional information:

Top 5 Most Populous Countries in Asia (2026):

1. India: ~1.46 billion
2. China: ~1.42 billion
3. Indonesia: ~272–285 million
4. Pakistan: ~240–251 million
5. Bangladesh: ~174 million

Last verified on 13-04-2026

Explanation

• Change from direct to indirect speech requires tense change.
• Present continuous → past continuous.
• “Today” changes to “that day”.
• “Said” changes to “told that”.
• Correct sentence: he was going to the store that day.

Last verified on 13-04-2026

Explanation

• Boyle’s Law describes the relationship between pressure and volume.
• At constant temperature, gas behaves in a specific way.
• Pressure increases when volume decreases.
• Pressure decreases when volume increases.
• Formula: P₁V₁ = P₂V₂

Explanation

• Bohr’s model states that electrons move in fixed energy levels (shells).
• These paths are also called orbits or stationary states.
• Each orbit has a definite energy.
• Electrons do not lose energy in these orbits.

Last verified on 12-04-2026

Explanation

• According to Charles’s Law, volume is directly proportional to temperature (in Kelvin).
• At constant pressure: V ∝ T.
• If temperature doubles, volume also doubles.
• Gas expands when heated.
• So, volume becomes double.

Last verified on 12-04-2026

Explanation

• Newton’s First Law is also called the Law of Inertia.
• A body remains at rest or in uniform motion.
• It continues unless an external unbalanced force acts on it.

Last verified on 12-04-2026

Explanation

20 years = 2 half-lives  

Fraction left = (1/2)² = 1/4  

Last verified on 12-04-2026

Explanation

For parallel: 1/R = 1/4 + 1/6 = 3/12 + 2/12 = 5/12  

R = 12/5 = 2.4 Ω  

Last verified on 12-04-2026