Measuring Physical Quantities

Physical quantities are measured using specific instruments to ensure accurate readings.

a. Measuring Mass

• Instrument: Triple Beam Balance
• Steps to Use:
  1. Place the balance on a flat surface, away from wind.
  2. Set all the masses to zero.
  3. Adjust the zeroing screw until the pointer is aligned at zero.
  4. Carefully place the object on the pan.
  5. Move the large mass (100g) until the beam topples, then move it back one step.
  6. Repeat with the medium mass (10g), then the small mass (1g).
  7. Read the mass by adding the values of the masses.
• Example: If the masses are positioned at 300g, 40g, and 5g, the total mass = 345g.

b. Measuring Volume

• Instrument: Measuring Cylinder
• Sizes: Available in sizes like 25ml, 50ml, 100ml, 500ml, and 1000ml.
• How to Read:
  1. Look at the bottom of the meniscus (curved surface of the liquid).
  2. Ensure you view the meniscus at eye level to avoid parallax error.

c. Measuring Temperature

• Instrument: Liquid-in-glass Thermometer
• How it Works:
  1. A thermometer has a sealed glass tube with liquid (mercury or alcohol). When heated, the liquid expands, and its top moves up the tube.
• Steps to Measure:
  1. Place the thermometer’s bulb below the liquid’s surface.
  2. Wait until the liquid stops expanding.
  3. Read the temperature where the liquid’s top is in the tube.

d. Measuring Time

• Instrument: Stopwatch (Digital)
• How to Use:
  • Press the start/stop button to start timing.
  • Press it again to stop timing.
  • Use the reset button to reset to zero.
• Reading Time:
  • Time is displayed as minutes: seconds: hundredths of a second.
  • Example: “11:14:01” means 11 minutes, 14 seconds, and 01 hundredth of a second.