## Pages

### SPA/Practical

Precision of instruments:
1) Ammeter (0-1A) - 0.01A ( example: 0.20A,0.21A)
2) Electronic balance - 0.01g (example: 121.10g, 121.11g)
3) Half metre rule or metre rule - 0.1cm ( example: 12.0cm, 12,1cm)
4) Measuring cylinder - 0.5cm3 (example: 18.0cm3,18.5 cm3)
5) Micrometer - 0.01mm ( example: 2.10mm,2.11mm)
6) Milliameter(0-100mA) - 1mA ( example: 20mA, 21mA)
7) Spring balance(0 - 10N) - 0.05N ( example: 3.65N, 3.70N)
8) Stopwatch (analogue) - 0.1s ( example: 36.0s,36.1s)
9) Stopwatch (digital) - 0.01s ( example: 28.11s)
10) Thermometer (-10oC to 110oC) - 0.5oC ( example: 23.0oC, 23.5oC)
11) Voltmeter (0-5V) - 0.05V ( example: 2.50V, 2.55V)
12) Protractor - 1o (example: 20o, 21o)

1)
A table of results, should include, in the heading of each column, the name or symbol of the measured or calculated quantity. together with the appropriate unit.
Example:

2) Each reading should be repeated, if possible, and recorded. There should be at least 5 sets of readings.

Raw data : Data obtained from the reading of the instument. The date must follow the precision of the instrument
Example: In the above table, V/V and I/A are the raw data.Since the precision of the voltmeter and the ammeter is 0.05V and 0.01A respectively, the readings can be 2.35V or 1.00V for voltmeter and  0.31A or 0.79A for ammeter.

1.34V , 4.31V is incorrect since the precision of the voltmeter is 0.05V. The last digit must be 0 or 5.
1.3 V , 4V is also incorrect as it must be written to 2 decimal places since the precision of the voltmeter is in 2 decimal places. It should be written as 1.30 V or 4.00 V.

Calculated quantity : The value calculated using the raw data based on formulas. Always leave calculated readings in 3 significant figures.
Example: In the above table, to calculate R=VI. R is the calculated quantity. R = 3.050.55=5.55 ( 3 significant figures)

Drawing graphs:

1) A graph should be drawn with a sharp pencil or mechanical pencil.

2) The axis should be labelled with quantities and units

3) The scales for the axes should allow the majority of the graph paper( more than half the graph paper) to be used in both directions and be based on sensible ratios. eg. 2 cm (10 smallest squares) on the graph paper representing 1, 2, 5, 10, 20 or 50 e.t.c units of the variable.
Example: Do not choose 2 cm to represent 3, 7, 8 e.t.c units.

4) Points should be indicated by a small cross.

5) Where a straight line is required to be drawn through the data points, there should be an equal number of points either side of the line over its entire length. That is, points should not be seen to lie all above the line at one end, and all below the line at the other end.
Example:

Video to show how to draw best fit line:

6) The gradient of a straight line should be taken by using a triangle with a hypotenuse that extends over at least half the length of the candidate's line. The data points should not be used as the corners of the triangle. All readings taken must be from the straight line drawn.

Leave the value of the gradient to 3 significant figures. Source: School Based Science Practical Assessment (SPA) Information Booklet.
7) Origin need not start from (0,0). Can start from eg, (4,5) but don't draw zig-zag lines.

Experiment demonstration on Refraction - Using optical pins and rectangular glass block

Experiment demonstration on Reflection - Using optical pins and mirror

Experiment demonstration on measuring Period of a pendulum