physics prac

Precision ● Ammeter — 0.01A ● Voltmeter — 0.05V ● Thermometer — 0.5C ● Metre ruler — 0.1cm or 0.001m ● Protractor — 1 deg ● Measuring cylinder — 0.5cm3 ● Spring balance —0.1N(for 0-10N), 0.01N(for 0.10N) ● Stopwatch — 0.1s ● Mass — 0.1g When asked to obtain average value, must draw out table of at least 3 different values and calculate average (follow dp) When asked to find period, find average of time taken for 20 oscillations, then divide by 20 again Graph - axis, scale, points, best fit, trend, range - Plot at least 5 readings for straight line and 8 readings for curve - Readings interpreted from graph should be read to half of the smallest square - MUST ALWAYS HAVE ORIGIN Table - Headings - Processed data follow sf of raw data - Dp of raw data follow instrument (must be same throughout the column) - Range must be more than 50% of instrument, eg metre ruler range must be more than 50cm Relationship between x and y - X is linearly related to y, with negative/positive gradient - Directly proportional - As x increases, b decreases at at a decreasing rate Precautions - [measurements] eye must be placed vertically above the scale when reading the ruler/protractor to avoid parallax error - [measurements] take reading over a few points and find average value - [pendulum] take 2 sets of readings per interval for 20 oscillations and find the average by dividing by 20 - [pendulum] the time for the first few swings should not be taken and only start timer when oscillations are steady

- [measuring volume of irregular solid] make sure solid is dry before lowering into liquid and ensure no liquid spillage or splashes when lowering the liquid - [circuits] circuit must be switched off when not in use so that heat is not produced in the resistance wire and also to conserve the emf of the batteries Source of error - [mechanics] the time taken for the oscillation is too short, causing inaccuracy in the timing due to human reaction time to be significant - [mechanics] difficulty to read the markings on the ruler as the strings with the loads are swaying - [mechanics] difficult to judge the exact position of where the metre rule is clamped - [mechanics] the difficulty to judge the position of the loop to be just above the ruler - [moments] the diameter of the pivot is large and errors will arise when drawing the lines to join the center to the pivot, making the centre of gravity located inaccurate - [moments] the string used to make the plumbline is