Measuring instruments(part 3 final)

Micrometer Screw Gauge

This instrument can measure up to 0.01mm and each division represents 0.5mm. The micrometer screw gauge is can be read using the following method:
1. Read the main scale reading at the edge of the thimble.
2. Take the thimble reading opposite the datum line of  the main scale.
3. The reading is found by adding the main scale reading to the thimble reading.
The zero error for the micrometer screw gauge is the same as the one for the vernier caliper.
 

Measuring instruments(part 2)

Vernier Calipers

We were shown how to use and what a vernier caliper is today. It is basically another instrument that can be used to measure the internal and external diameter. This instrument is able to measure up to an accuracy of 0.01cm or 0.1mm. Reading this instrument is no easy task but after a few tries, i managed to master it. The method of reading are as follows: 

1. Close the jaws and ensure that the zeros are present on both the vernier and main scale to form a straight line.

2. Jaws are then adjusted and clamped onto the object to be measured.

3. Note the reading on the main scale and the vernier scale.

4. Final reading=main scale reading + vernier scale reading

However, this is not the end yet because when the vernier caliper is shut, there may be a ZERO ERROR. This error may be a positive zero error or a negative zero error. 

POSITIVE ZERO ERROR

The zero mark of the scale lies on the right side of the main scale when the caliper is shut so the reading will be: Actual reading =initial reading-zero error

NEGATIVE ZERO ERROR

The zero mark of the scale lies on the left side of the main scale when the caliper is shut so the reading will be: Actual reading=initial reading+zero error

Measuring instruments(part 1)

Length measurements

The metre ruler is a tool that we would use quite often in our school lives but it is only accurate to 0.1cm and you cannot make measurements that are less than 1 decimals place. You may think that reading a metre ruler is very simple but there is more than meets the eye. I learnt about parallax errors and this can happen when reading a metre ruler of reading the water level of a measuring cylinder. This is caused by the positioning of the eye and make affect your results hence it is very important that you know the right way of reading the metre ruler order to prevent such an error. Firstly, we have to position our eye vertical or perpendicular to the mark and for a measuring cylinder, the water level has to be at your eye level. Here is picture to illustrate

how.

Prefixes for SI Units

Why do we use SI units?

These prefixes are used for the sake of convenience as sometimes, we have to measure numbers that have to do with nanotechnology and thus it would be cumbersome to mention this quantity a number of times. These SI units are are important and can be applied at the later part of our lives. Thus I take it upon myself to memorize the prefixes and what they stand for. This is a simple table that will illustrate what i have said.

Physical quantities and units

SI units

SI units defines 7 base quantities and units.
QUANTITIES                                UNITS
Time-> t                                second-> s
Length-> l                              metre-> m
Mass-> m                              kilogram-> kg
Temperature-> T                    kelvin-> K
Electric current-> I                 ampere-> A
Amount of substance-> n        mole-> mol
Luminous intensity                   candela-> cd

We use prefixes for SI units such as tera, giga, mega, kilo, deci etc. They all are representations of the standard forms.

Basic Laboratory Orientation

What should you do when in the laboratory.

1) When you accidentally spill some strong acid onto your skin, you should wash it thoroughly with plenty of water.

2) If there is excess acid from your experiment, you should pour the acid into a special bottle meant for disposal and follow instructions from the teacher.

3) A non-luminous flame should not be left alone as it cannot be seen easily and other people might not see the flame and burn themselves.

4) The best way to light a Bunsen burner is to open the air-hole ignite a lighter near the mouth of the barrel and turn on the gas tap slowly.

5) Adult supervision is required for students to enter the science laboratory as the laboratory can be a dangerous place if the users are not careful.

6) You should not run around in the laboratory as the laboratory is very dangerous as they might be injured.
7) If there is anything broken in the laboratory, the teacher must be informed immediately as others may get hurt.

Graphs

Graphing Scientific Data

Sometimes, we plot scientific data that is recorded in a graph format. The graph is made up of the x and y-axis and at the top of the graph, it is usually the y-axis against the x-axis. We have to scale the graph so that it covers about 3/4 of the page. Scales should not differ by multiples of 3 as well. Each of the graph points has to be marked by an X. We don't connect all of the points but we either draw a best fit line or a best fit curve. We draw the best fit line by drawing the line in the average of the points. If one of the scales has 1 d.p., the rest of the scales must also have 1 d.p.