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Physics Practical

 

Introduction 

In this article, I will explain to you everything you need to know on how to conduct physics practicals. 

physics practical
physics calculations

Conducting physics practicals simply refers to carrying out an experiment in the laboratory to confirm the factual evidence of a theory.

You carry out a series of experiments to accumulate data for comparison. Thereafter, you plot a graph to calculate the gradient. 

Guidelines on how to conduct physics practicals would be given to you so that you don’t end up making mistakes. 

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What is the difference between Theory and Experiment

When we talk about theory, we are simply referring to a statement of fact due to the availability of experimental evidence to support it. A theory may be disapproved if there is no experimental evidence to support it.

Whenever we come up with a theory, we need to perform an experiment to ascertain its existence. 

By performing an experiment, we will be able to monitor and accumulate data that can support the theory we earlier came up with. 

The theory is an idea, while an experiment is practical that supports the existence of the idea. 

How to Report a physics Experiment  

Here are the procedures one needs to follow to report a physics experiment:

  1. You need to come up with a title for the Experiment
  2. The next step is to write the aim of your experiment. 
  3. You now mention the names of the apparatuses you use for the experiment. 
  4. Draw a diagram of how the apparatuses were set up and label your diagram 
  5.  Draw a table for recording your data 
  6. Fill in the table with the results you obtain from the series of individual experiments. 
  7. State the theory of the experiment to back up your reason why the procedures and the readings are mandatory. 
  8. Apply the equation you need to make certain calculations to come up with your readings 
  9. Draw your graph 
  10. Find the gradient or slope of the graph 
  11. In some cases, you may also need to apply the result from your slope to make calculations. The formula will be given to you. 
  12. State the precautions you observed while carrying out the practical to get an accurate reading. 
  13. You also need to avoid common errors while carrying out a physics experiment. 
  14. Additionally, you need to wear a lab coat before entering the Physics Laboratory. You need to focus on your practical skills to avoid making unnecessary mistakes. 

How to Plot and Calculate a Graph 

To plot a beautiful graph, you will need to maintain calmness and concentrate on the practical. By plotting a graph, you will understand the accuracy of your data. 

The aim of plotting a graph is to show the relationship between variable quantities during physics practicals.

After plotting a graph, you will need to find the following:

  • Gradient or slope 
  • The intercept on the x-axis or y-axis.
  • Apply any of the formulas they give you to make your deductions. 

The items you will need to plot a graph include:

  • A set of mathematical set
  • A sharp pencil 
  • A transparent ruler 
  • A razor or sharpener 
  • A neat graph book 
  • A broomstick for drawing curves 
  • A biro 

What types of graphs we can plot?

To understand how to conduct physics practicals, we must first know three types of graphs and they are:

  1. Straight line graphs
  2. A parabola or quadratic curve 
  3. An inverse graph 

How to Calculate the Slope or Gradient of a Graph

To find a slope of a graph, follow the following steps:

  1. On the graph, there is an x-axis and a y-axis
  2. They form a plane
  3.  The y-axis is on the vertical line of the graph
  4.  Also, the  x-axis is on the horizontal line of the graph
  5.  The y-axis is connected to the x-axis at the zero point
  6.   Also, the line that goes up, starting from zero is a positive y-axis
  7.   Additionally, the line that goes right, starting from zero is a positive X-axis
  8. We also have another line that moves down. This is a negative y-axis.
  9. From the left side of the plane, we have a negative X-axis
  10. Indicate your readings on the appropriate axis (y-axis and x-axis)
  11. Use a transparent ruler to connect the readings on the y-axis and the x-axis
  12. Apply the same ruler to draw a straight line between the two axis
  13. Ensure to apply pencil throughout your work
  14. Select two points on the line you have drawn with the ruler
  15. Connect the two lines to find your slope
  16. You need to know that Y = mx + c, where c is the intercept.
  17. This is how to calculate your slope by using [ Slope, S = (y2 – y1) / (x2 – x1)] 
  18. The plane is as (x , y)
  19. You can show coordinate points as M (x2 – x1) and N (y2 – y1)
  20. Subtract y1 from y2
  21. Also, subtract x1 from x2
  22. Divide (y2 – y1) by (x2 – x1) to get the slope 
  23. We also know slope as a gradient

How to Find an Intercept on a Graph

To find an intercept, you will have to extend the plotted line to cut through the y-axis or x-axis. The scale at which the plotted line cuts through any of the axis is the intercept of the graph. 

The graph should start from the origin at (0,0) for you to find the intercept. 

What are the Common Errors you Might Notice During Physics Practical

The common errors you need to avoid while carrying out physics practicals are:

  • Systematic Errors 
  • Random Errors 
  • Erratic Errors 
  • Zero Errors 
  1. Systematic Error is an error due to unforeseen circumstances like faulty lab apparatus and a blowing fan. 
  2. Random error is an error caused by poor judgment while reading the data.
  3. Erratic error is the type of error due to a lack of focus by the person doing the experiment. 
  4. Zero error is the type of error due to a bad pointer in an apparatus or faded calibration.

A sample of How to Conduct Physics Practical

Here is a sample of a question and answer on how to conduct physics practicals from West African Examination Council (WASSCE) – 2008

Question

You are provided with a uniform meter rule, a knife edge, masses, and other necessary apparatus.

  1. Suspend a meter rule horizontally on the knife edge. Read and record the point of balance G of the meter rule. keep the knife edge at this point throughout the experiment.
  2. Using the thread provided, suspend the object labeled W at the 15cm mark of the meter rule.
  3. Suspend a mass M of 20g on the other side of G. Adjust the position of the mass until the meter rule balances horizontally again.
  4. Read and record the position Y of the Mass M on the meter rule.
  5. Determine and record the distance L between the mass and G. Also, determine and record the distance D between W and G.
  6. Repeat the procedure for four other values of M = 30, 40, 50, and 60g. In each case, ensure that W is kept constant at the 15cm mark and the knife edge at G.
  7. Evaluate L-1 in each case. Tabulate your readings.
  8. Plot a graph of M on the vertical axis against L-1 on the horizontal axis
  9. Determine the slope, S, of the graph.
  10. Evaluate S/D
  11. State two precautions are taken to obtain accurate results.

Solution

Here is the solution to the above question

Aim of the practical

An experiment to determine the equilibrium of a meter rule with several masses.

Table for the experiment

where G = 49.50cm, D = 34.50cm

M(g)Y(cm)L(cm)L-1 (cm-1)
20.0099.2549.750.020
30.0084.0034.50.030
40.0075.3725.870.040
50.0070.2020.700.050
60.0066.7517.250.060
Table for meter rule experiment
how to conduct physics practical
Graph

Slope

To find the slope, we say 

\frac{y_2-y_1}{x_2-x_1}

Therefore, the slope, S, is equal to 

\frac{(60\;-\;20)}{(0.05\;-\;0.02)}

S = 1333.3gcm

To find S/D we now say

S/D = 1333/34.5 = 35

Precautions

  1. I ensure that all fans are switched off to avoid breeze from affecting the stability of the meter rule
  2. I ensured that the mass is properly hung on the required calibration.

Reference:

BBC

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