Practical Quick Revision
Category Archives: Practical Skills
How to read the voltmeter
In the lab, usually we use these two types of voltmeter. One with a range of 0 to 3 V and the other with a range of 0 to 5 V.
Watch the video to learn how to read the respective voltmeter and how to record the reading.
How to read digital micrometer screw gauge
Refer to this link on the analogue micrometer screw gauge
https://youtu.be/jqvYjaOUa20
Reading micrometer screw gauge practice
https://youtu.be/S1Mvb5kHnJg
How to read measuring cyclinder
Physics Practical – Graph Plotting ASPL
In general, the plotting of graph for Physics practical is usually 4 marks.
The break down of the 4 marks are as below:
- A: axes (label the axes with physical quanity / units, and the vertical and horizontal lines drawn)
- S: scale (ensure 1st and last point occur more than half of the graph paper, just scale with 2 cm is to either 1, 2 or 5 units)
- P: points (plot the points clearly on the graph with crosses ‘x’)
- L: best fit line or best fit curve based on the points.
Go through the video to have a better idea on how to plot the graph and get the marks.
Drawing the best fit line or curve
1st Electricity Experiment
Below is a simple electrical experiment to determine the resistance of the unknown resistor. Take some time to look through these series of video to have a better understanding on how to do the connection and taking readings from the instruments.
Refer to this blog post for better understanding of the experiment and some information on ohmic conductor.
Finding unknown resistor R and setting up the electrical circuit
Basic set up
If Connections of Ammeter/Voltmeter are swopped
Different types of connecting wires
Connecting Variable Resistor
How To Read An Ammeter
How to Read A Voltmeter
Pins inside and outside of beaker filled with water – 2012 sciphy practical
A pin in the beaker of water appears higher than its actual position due to refraction of light.
In this experiment, you have to adjust the pin at the cork to a suitable height, such that the pin and the image of the pin inside the beaker of water is aligned and that ‘pins at position of no parallax’ position.
The video below guides you in adjusting the height of the pins to locate correct height.
Similar kind of experiment: Pins with Lens and mirror
Practical – Lens Experiment
The video below shows a typical lens experiment. (reference to O-Level SciPhy 2015). I will briefly go through the set-up, main steps and how to get the 1st set of readings.
In the next video, it highlights the various types of lens practical which you might have in the school lab. e.g. different kind of crossed-wire, a beaker of water as a converging lens and different kind of images formed.
Key points:
1) Make sure the object (illuminated crossed-wire), lens and screen are aligned properly.
2) Source of Error: identifying the sharpest image
Improvement: (i) Repeat the experiment a few times for the same
independent variable to identify the sharpest image.
(ii) Move the lens (or screen) forward and backward about
the sharp image, until the sharpest image is determined.
3) In general, the focal lens of the lens used in the lab is usually 10 cm or 15 cm. Most lens experiment requires you to find the focal length. There is also a easy way to quickly determine the focal length before starting the experiment.
Refer to this post for another lens experiment which is different and more challenging.
Centre of Gravity
Simple electric circuit set up
This simple circuit involves a resistance wire on the meter rule and the use of jockey tapping at different length L on the resistance wire.
Note that this is not a potential divider. Rather this set up works like a variable resistor (rheostat) in the circuit. When the switch is closed (jockey NOT tapping on resistance wire), there is no current flowing as voltmeter (infinity resistance) is connected in series with the ammeter and the battery. Hence the voltmeter is showing the battery’s electromotive force (emf) of 3.0 V.
When the switch is closed and the jockey is tapped on the resistance wire on the ruler, the longer the L (length of resistance wire), the higher the resistance of the circuit, the higher the potential difference (voltmeter) across the resistance wire and the smaller the current through the ammeter. Hence the tapping of the jockey on the resistance wire is similar to adjusting the resistance on the variable resistor.
(If you are wondering why the voltmeter is not showing the emf of the battery when the jockey touches the resistance wire L, it is because in reality there is internal resistance in the battery or even in the connecting copper wire. For olevel theory we assume no internal battery resistance or resistance in copper wire or ammeter).
To learn how to set up the experiment, refer to the video below.
Both ammeter and voltmeter have two terminals, (positive and negative). The conventional current must flow into the positive terminal (+) of the meters and out of the negative terminal (-). If the connection is the opposite, the needle will deflect below the zero marking. Refer to the video below.
Sometimes, the connection terminals on the voltmeter and ammeter are different. Likewise, different types of wire with different connection heads have to be used. Refer to the video to see how are they connected in general.
Click here for another set up of a simple electrical circuit to determine the unknown resistor.
Setting up a retort stand and pendulum experiment
In this post, we will be going to the basics of setting up the retort stand and pendulum experiment. Most probably, this will be the first experiment which you will perform in the lab. Let’s start with the setting up the retort stand, boss and the clamp.
Next we will take a look at how you set the up the apparatus for the pendulum experiment.
How is the period affected by length, mass of bob, and angle of release? Click on this post to find out more.
Click here to see how to use a digital stopwatch.
Factors that affect the period T of a pendulum
Period, T, is the time taken for one complete oscillation.
The period T of a pendulum is affected by the following factors.
1) the length of the pendulum:
– the longer the length, the longer the period (i.e. swing slower)
2) the gravitational field strength, g
– the greater the g, the shorter the period (i.e. swing faster)
(e.g. the g on earth is 10 N/kg while that on the moon is 1.6 N/kg, hence the period on      the moon will be longer)
NOTE: (common misconceptions)
Period, T, of the pendulum is NOTÂ affected by
1) the angle of release (as long as the angle of release is between 10 to 15 degrees)
(if the angle of release is small, the swing will not be fast and air resistance will not be     significant)
2) the mass of the pendulum ball
Refer to the video below for the demonstration of the above concepts.
Pendulum: Displacement-time vs KE-time graphs
How to set up the pendulum experiment?
Click here to view the video
Evan's Space 