General Physics

Question 1

SI Units

Answer 1

Kilogram ( Kg) - Unit of mass
Second (s) - Unit of time
Ampere (A) - Unit of electric current
Kelvin (K) - Unit of thermodynamic temperature
mole (mol) - Unit of the amount of substance
Candela (cd) - Unit of luminous intensity

Question 2

Uncertainty

Answer 2

• Three possible uncertainties, these are uncertainty, Percentage uncertainty and Absolute Uncertainty.
• Uncertainty is the difference between the measured value and the true value of the quantity.
• Percentage uncertainty is similar to Uncertainty but is instead given as a percentage
• Absolute Uncertainty is the possible difference from the true value given as a fixed number in the unit of measurement

Question 3

Error's & Measurements
(What are the three main errors?)
(What causes these three main errors?)
(What are the four main types of measurements?)
(What do these measurements mean?)

Answer 3

• There are three main errors which are needed to be understood for the exam, these are random error, systematic error and zero error
• The random error is an error that causes reading to be spread about the true value, due to the varying in an unpredictable way between measurements
• The systematic error is an error that causes reading to be different from the true value by a consistent amount
• A zero error is an error caused by a measuring error where an instrument does not read zero when it should
• If an error is not affected by any of these measurements, it could be known as an ‘accurate measurement’, which is a measurement that is close to the true (accepted) value
• apart from accurate measurements, there are precise measurements, repeatable measurements and reproducible measurements.
• Precise measurements are measurement where there is very little spread about the mean
• Repeatable measurements are measurements where the same results are obtained if the original experiment repeats the measurements using the same equipment and method
• Reproducible measurements are measurements where similar results are obtained if a different experiment carries out the measurements using a different method and/or equipment