Physics Chemistry & Biology Test 7
1. Which metal is used in making coins ?
  • Iron
  • Coppery
  • Sodium
  • Mercury
Explanation: Copper is widely used for making coins because it is strong, corrosion-resistant, and easy to shape. Modern coins often use copper alloys like bronze or cupronickel for durability and shine.
Which instrument is used to measure electric potential difference ?
  • Ammeter
  • Voltmeter
  • Galvanometer
  • Barometer
Explanation: A voltmeter measures the electric potential difference (voltage) between two points in a circuit. It is connected in parallel and shows how much energy per charge is transferred.
What is dry ice ?
  • Solid CO₂
  • Frozen nitrogen
  • Ice without water
  • Mixture of salts
Explanation: Dry ice is solid carbon dioxide, which changes directly from solid to gas (sublimation). It is used for cooling, fog effects, and preserving food since it leaves no liquid.
Which vitamin is produced in the body by sunlight ?
  • Vitamin A
  • Vitamin B
  • Vitamin C
  • Vitamin D
Explanation: When skin is exposed to sunlight, ultraviolet rays help the body produce vitamin D, which is essential for bone strength, calcium absorption, and prevents rickets and osteoporosis.
Which blood group is known as universal donor ?
  • A
  • B
  • AB
  • O
Explanation: Blood group O is called the universal donor because its red blood cells lack A and B antigens, making it safe to donate to any other blood group without reaction.
Which device is used to measure temperature ?
  • Barometer
  • Thermometer
  • Ammeter
  • Hygrometer
Explanation: A thermometer measures temperature using substances like mercury or alcohol that expand with heat. It is used in homes, laboratories, and hospitals to check body and environmental temperatures.
Which gas is essential for respiration ?
  • Hydrogen
    • Explanation: Oxygen is vital for respiration, the process where living organisms break down food molecules to release energy. It helps produce ATP, the main energy source in body cells.