Explanation

• O⁻ (O Negative) is the universal donor blood group.
• It can be transfused to A, B, AB, and O blood groups.
• O⁻ blood lacks A, B, and Rh (D) antigens.

Additional information:

• Universal Recipient: AB⁺ (AB Positive)
• ABO Blood Groups: A, B, AB, O
• Rh Types: Positive (+) and Negative (−)
• Total Common Blood Groups: 8 (A⁺, A⁻, B⁺, B⁻, AB⁺, AB⁻, O⁺, O⁻)

Last verified on 14-07-2026

Explanation

• The SI unit of electric current is Ampere (A).
• Electric current measures the flow of electric charge.
• Defined using the elementary charge (e = 1.602176634 × 10⁻¹⁹ C).
• Named after: André-Marie Ampère (scientist).
• 1 Ampere = 1 Coulomb per second (1 A = 1 C/s).

Last verified on 08-06-2026

Explanation

• 24-karat (24K) gold is considered the "best"
• Purity: 99.9% pure gold.
• Color: Rich, deep, bright yellow.

Additional information

• 22K Gold: 91.7% pure gold. It is mixed with harder metals like silver or copper.
• 18K Gold: 75% pure gold. It is highly durable and excellent for diamond settings 
• Carat is the unit of measurement for the physical weight of diamonds/gold.

Last updated by NA on 16-07-2026

Explanation

• Oranges are well-known for being rich in Vitamin C.
• It is essential for immune function, skin health, and other bodily processes.

Additional information 

• Vitamins are essential nutrients
• That your body requires in small amounts to function, grow, and develop properly.
• They are divided into two main groups:
• water-soluble (like Vitamin C and the B-vitamins)
• fat-soluble (like Vitamin A, D, E, and K)

Last updated by NA on 16-07-2026

Explanation

• In a nuclear reactor, energy is produced due to a controlled chain reaction.
• A controlled chain reaction releases energy steadily and safely.
• Control rods are used to regulate the number of neutrons and prevent excessive reactions.
• This controlled process is used to generate electricity in nuclear power plants.

Additional information:

• An uncontrolled chain reaction occurs in nuclear bombs.

Last verified on 11-07-2026

Explanation

• A Barometer is an instrument used to measure air (atmospheric) pressure.
• It helps in weather forecasting by measuring changes in atmospheric pressure.
• The mercury barometer is the oldest type of barometer.
• It was invented by Evangelista Torricelli in 1643.
• Barometers are widely used in meteorology and aviation.

Last verified on 09-07-2026

Explanation

• A Fathometer is used to measure the depth of the ocean, sea, or any body of water.
• It determines the distance from the water surface to the seabed.
• The instrument works using sound waves (echo sounding).
• It measures the time taken for sound waves to travel to the seabed and return.

Additional information:

• Galvanometer → Measures electric current
• Barometer → Measures atmospheric pressure
• Thermometer → Measures temperature
• Hygrometer → Measures humidity

Last verified on 06-07-2026

Explanation

• Sir James Chadwick discovered the neutron in 1932.
• He was a British physicist.
• His discovery completed the basic picture of the atomic nucleus.
• He received the Nobel Prize in Physics in 1935 for this discovery.

Additional information:

• J. J. Thomson – Electron (1897)
• Ernest Rutherford – Atomic nucleus (1911) and Proton (1917)

Last verified on 03-07-2026

Explanation

• The magnitude of an earthquake is measured by the Richter scale.
• It measures the energy released by an earthquake.
• The Richter scale was developed in 1935 by Charles F. Richter.
• It is used in seismology (the study of earthquakes).

Last verified on 30-06-2026

Explanation

• Nitrogen (N₂) → 78%

Additional information:

• Oxygen (O₂) → 21%
• Argon (Ar) → 0.93%
• Carbon dioxide (CO₂) → 0.04% (approximately)
• Other gases → Trace amounts

Last verified on 28-06-2026