Practical

Practical

1. Measuring tools

   • 1. measuring tape for distances
   • 2. micrometer for small lengths and thickness
   • 3. stopwatch for time intervals
   • 4 thermometers for temperatures
   • 5. balance for masses
   • 6. ammeter for current intensity
   • 7. voltmeter for potential difference

2. Precautions

   • Mistakes and errors
     • Systematic experimental errors
       • Parallax error occur by looking with an angle to the scale
         • Align of eyes perpendicular to the scale
       • Zero error when the scale does not start from zero
         • Pre-calibrating instruments to adjust future readings and use of zero reset button
     • Uncertainties of measurements as the exact value cannot be justified (specific significant figure) and precise
       • the result is accurate if it close to the true value of quantity
     • Insufficiently controlled values that affect the dependant value
     • Random human errors of measuring and recording
   • Safety
     • 1. Eye protection
     • 2. Safe support
     • 3. Low current dry wires
     • 5. Springs may snap so wear goggles for protection
     • 4. Wear heat resistance gloves
     • 6. when dealing with mains of electricity (ripple tank, ticker tape, DC power supply) avoid using with wet hands for water
     • 7. dropping of heavy objects on people
   • Repeat the experiment and take averge
   • Respect to the reactio time so take reading of several takes then divide to be closer to the true value
   • Get rid of anomalous results

3. Experimental accuracy

   • If the values have differences less than 10% they are close enough to be accepted within the limit of experimental accuracy
   • If the values have difference more than 10% they are too far to be explained within the limit of experimental accuracy

4. Variables

   • Independent variable is changed by the experimenter to know its effect plotted on X-axis
   • Dependent variable is the outcome that is measured from the experiment each time the independent variable is changed plotted on the Y-axis
   • The control variables can affect the dependent variable, so they need to be kept constant during the experiment for accuracy (environmental conditions)

5. The Reaction time is the square root of the distance traveled over 10 m/s^2

6. Experimental investigations

   • 1. question and hypothesis
   • 2. planing the investigation
     • A. identify the independent variable different quantities and how to change them
     • B. identify dependent variable quantity and how to measure it and work it out
     • C. identify controlled variables and how to be controlled suffeciently
     • D. equipment and apparati needed
   • 3. procedure with a labled diagram
     • A. set the experiment as shown
     • B. follow the plan
     • C. repeat the measurements two more times
     • D. repeat the steps for new changes values
     • E. record results and workout the end value according to the average values