O Level Pure Physics Practical Tips: What to Look Out For
The O Level Pure Physics practical exam can be anxiety-inducing for many students. From setting up apparatus to accurately collecting and analysing data under pressure, there are numerous factors that can affect performance.
This guide outlines the key areas to focus on during revision and offers targeted tips for common Physics practical questions. With adequate preparation and knowledge of core concepts, students can gain confidence to tackle this challenging component of the Pure Physics exam.
1. Master Key Concepts
Concepts are fundamental building blocks representing basic ideas such as Force, mass, distance, and time. Understanding the underlying principles helps students effectively design, conduct, analyse, and troubleshoot problems.
For example, in experiments involving heat transfer and thermal equilibrium, students should understand how different materials with varying specific heat capacities affect the final temperature when they are brought into thermal contact. By understanding this relationship, they can predict and explain how the mass of each material and the initial temperatures interact to determine the final equilibrium temperature.
The use of units and symbols is crucial for defining and working with physics concepts and should be learned together. They provide a shorthand for formulas and a standardised system to measure quantities consistently, such as Joules (J), kilograms (kg), and degrees Celsius (°C).
True understanding goes beyond rote memorisation. Students can confidently tackle unfamiliar problems and scenarios in the practical exam without panicking when they grasp the fundamental principles and concepts.
2. Memorise Theory and Learn to Use Equipment
Theories are built on concepts. They are explanatory frameworks that explain why and how physical phenomena occur. The most effective Physics practical exam preparations connect theoretical knowledge with practical application.
Each topic in the Pure Physics syllabus has relevant formulas, definitions, and equations. Students should compile all relevant equations and formulae in one place for easy revision.
Students must also combine theory with hands-on practice to understand why they are doing the experiment and what the results should indicate. Lab sessions also teach students these important lessons:
Safe selection and handling of lab equipment
Development of experiment planning skills
Understanding the order of operations in experiments
Precise measurement taking
Familiarity and efficiency in conducting common experiments
Strategies for avoiding common mistakes and errors during practical exams
3. Visualise Problems with Diagrams
Drawing or sketching diagrams is a powerful technique that helps students understand, analyse, and develop problem-solving plans. Visualising problems on paper is a good habit to develop and can be used when practising in a lab or at home without equipment. Developing these visualisation skills helps a student to:
Organise information and plan a solution
Simplify complex scenarios or break multi-step questions into a tangible form
Minimise misinterpretations and identify potential mistakes
Explain their problem-solving approach to the examiner
Visually represent theoretical concepts such as forces, change in motion, and directional movement, for example, with arrows
In some rare cases, examiners are giving marks for workings that include calculations, experiment setups, units, and measurements
4. Practice Graphs and Tables
Graphs and tables are essential tools for analysing data and communicating findings. Students are often asked to draw graphs and tables to solve problems using numerical or other data.
Practise drawing them with scenarios from textbooks or past papers:
Draw graphs carefully with sharp or mechanical pencils. Neatness and accuracy go hand-in-hand
Understand the roles of variables • Independent variables: the elements altered during an experiment (x-axis) • Dependent variables: the outcomes or measured responses (y-axis)
Choose an appropriate scale and use sensible ratios (e.g., 2cm representing 1, 2, or 5 units) to make it easy to interpret
Label axes clearly with their quantity and unit in this format: title (units)
The origin of a graph does not always have to start from (0,0) as long as it effectively communicates the results of the experiment
Denote points precisely with small crosses or ‘x’
Practice drawing best-fit lines to represent relationships and overall data trends (linear, curved, etc.)
Add a short, descriptive title at the top of each graph
Common O-Level Physics Practical Questions
This section covers the most common exam questions in the Pure Physics practical paper, helping you become familiar with key areas like Newtonian mechanics, optics, and electrical circuits.
I. General Physics
Measuring the Period of a Pendulum
Pendulums are often used to demonstrate perfect energy transfers. Students have to measure the period of a simple pendulum with a stopwatch. Given apparatus might include a metre rule, pendulum, a retort stand with clamp, and split cork.
Key concepts
The period refers to the time it takes for one complete oscillation
The longer the string of a pendulum, the longer its period
Common sources of error include the impact of air resistance and friction at the pivot point, both of which increase the period slightly with each oscillation
Practical tips
Formula for the period of a pendulum: T=2π√L/g • T (period) • π (pi) • l (length of string) • g (acceleration due to gravity)
Repeat the experiment several times to get the average time for one oscillation to reduce the impact of human reaction time and random errors
Start timing when the oscillations are steady and regular
Always keep the string straight when moving the pendulum or measuring the height from the bob to the experiment surface/table
h can be measured more accurately by using a set square to check that the metre rule is perpendicular to the surface and drawing a line to measure h from the middle of the pendulum to the surface.
Do not push the pendulum. Instead, release it from a small angle
Spring Extensions
Springs are often used to demonstrate a clear and predictable relationship between force, extension, and compression (also known as Hooke’s Law).
Key concepts
Applying a force to an object can cause it to change shape, bend, stretch, compress, or a combination of these.
The force needed to extend or compress a spring is directly proportional to the extension or compression as long as the spring's elastic limit is not exceeded
To calculate the force on the spring, multiply the mass on it (in kg) by 9.81N/kg (the gravitational field strength)
Extension = length - unloaded length
Practical tips
Repeat the experiment a few times to take the averages (more accurate)
Keep the ruler vertical to increase the accuracy of measurements
Graph axes: Force (N) on the x-axis and extension (mm) on the y-axis
Moment
The Principle of Moments describes how forces cause objects to rotate. Imagine a balanced seesaw: the principle of moments explains how the weights and positions of people on either side keep it from rotating.
Key concepts
Principle of Moments: For an object to be in rotational equilibrium, the clockwise and anticlockwise moments about any point must be equal
Moment = Fd • F (force, measured in N) • d (perpendicular distance from the pivot)
Moments (or torque) can act in two directions: clockwise and anticlockwise. It's crucial to correctly identify the direction of each Moment
Equilibrium is a state with no net turning effect and no net force acting on an object
By adding weights systematically to achieve balance, students can observe that equilibrium is only reached when the clockwise and anticlockwise moments about the pivot are equal
Practical tips
Accurately position the pivot, weights, and measuring distances
Carefully adjust the position of weights to achieve equilibrium
Use a ruler with suitable precision (e.g., a millimetre scale)
Measure the distance from the pivot to the lines of action of the forces perpendicularly
Use the provided gravitational field strength in your calculations (usually taken as 10 N/kg)
Minimise friction at the pivot point
Repeat readings to improve reliability
Gravitational Acceleration
Experiments to determine the acceleration due to gravity may come in a few formats, such as a pendulum suspended from a retort stand or dropping an object from a known height.
Key concepts
Free fall: Objects near the Earth’s surface accelerate downwards due to gravity. It is often denoted with ‘g’ (~9.8m/s2)
The formula for free fall: h=1/2gt^2
The graph should be a straight line if the object has a constant acceleration
Practical tips
Minimise wind, drafts, or external forces that could affect the motion of the object
Prepare your data in a table, recording the distance or height (h) and time taken (t)
Repeat the experiment multiple times with different heights or string lengths to identify any outliers
Thermal Physics
Specific Heat Capacity
Heating a material increases the kinetic energy of its molecules, causing them to move faster and resulting in a higher temperature.
Key concepts
Definition of specific heat capacity: the energy required to raise one kilogram (kg) of a material by one degree Celsius (°C)
Temperature reflects the average kinetic energy of the molecules within a substance
The amount of energy required depends on the mass and substance of the material and the desired temperature change.
Some materials require less energy to change temperatures. For example, lead (129 J/kg°C) versus wood (1700 J/kg°C)
Measuring the temperature rise alone isn't enough to determine the change in thermal energy. The mass of the material and its specific heat capacity also play crucial roles in how much heat is required to raise the temperature
Practical tips
Formula to calculate the amount of thermal energy required: change in thermal energy (J)= mass (kg) × specific heat capacity (J/kg°C) × change in temperature (°C)
Use an apparatus suitable for measuring the specific heat capacity of the sample material
Handle hot materials and temperatures with care
Total Internal Reflection in Semi-Circle Glass Block
This experiment allows students to visualise and measure the critical angle and understand the conditions required for total internal reflection (TIR).
Key concepts
TIR occurs when the angle of incidence exceeds the critical angle; the light ray is completely reflected into the denser medium
Refraction: The bending of light as it passes from one medium to another due to a change in speed (i.e., from air to glass)
Refractive index: a measure of how much a medium slows light down (a higher number means light travels slower)
Critical angle: The angle of incidence at which the refracted ray travels along the boundary between the two media
Snell’s Law: the relationship between the angle of incidence (i) and the angle of refraction (r) for light passing between two media with different refractive indices (n₁ and n₂): n₁sin(i) = n₂sin(r)
Semi-circular glass or perspex blocks are ideal as the flat surface makes it easy to clearly observe the refracted ray and the transition to total internal reflection
Practical tips
Aim the light ray at the centre of the flat surface to ensure it hits the curved surface at a perpendicular angle (avoiding refraction at that point)
Gradually increase the angle of incidence to observe and measure the gradual change in the refracted ray
Find the critical angle by carefully identifying the point where the refracted ray travels along the flat surface
Take multiple measurements of the critical angle to calculate an average
Avoid parallax error by ensuring your eye is directly above the protractor
Keep the glass block in the same position when tracing and measuring angles
Once you know the critical angle (c) and the refractive index of the medium (n₁), calculate the refractive index of the block (n₂) using Snell’s Law: n₂ = n₁ / sin(c)
Converging lens to form a sharp image
A converging (or convex) lens forms an image by refracting (bending) light rays that pass through it. The type of image formed (real or virtual, upright or inverted, magnified or diminished) depends on the object's position relative to the lens.
Key concepts
The focal length (f) is the distance between the lens and the point where parallel rays of light converge after passing through the lens
Lens Formula: The relationship between the object distance (u), image distance (v), and focal length (f) is given by the lens formula: 1/f = 1/u + 1/v
The primary way to achieve a sharp image is to ensure that the object, lens, and screen are positioned according to the lens formula
Practical tips
For a real image, the object must be placed beyond the focal point of the lens
To make the image sharper, students may adjust the screen position without moving the lens and object
Positioning the screen at the correct image distance (v) as determined by the lens formula and the object distance (u) allows students to find the exact point where the light rays converge to form a clear image
Ensure that the light source is stable to avoid errors
Use a clean lens to avoid optical distortions
Position the screen perpendicular to the light rays and align the lens correctly
Avoid parallax error in measurements by ensuring that your eye is directly above the measurement point and measurements are taken perpendicular to the screen
Water Wave in Tank
A shallow tray of water may be used to measure and calculate the speed of water waves.
Key concepts
Wave speed is the speed at which a wave travels through a medium. It is determined by the properties of the medium (in this experiment, the water)
The concept of wave motion is the transfer of energy without transferring matter. In this experiment, the water molecules move up and down as the wave passes but don't travel across the tank/tub.
Equation: Speed = Distance / Time.
Practical tips
Create ripples gently with a ruler or other provided apparatus
Avoid splashing or creating turbulent waves
Measure the distance the waves travelled along the length of the tank
Start the timer as soon as you create the wave and stop it the moment the crest reaches the other end
Focus on timing the wave crest
Keep the water depth consistent throughout the experiment
III. Waves
Light Refraction in Glass Block
Students are tasked to investigate the refraction of light through a glass block. The angle of refraction is always smaller than the angle of incidence because light slows down in glass (higher density than air).
Key concepts
Refraction: The bending of light as it passes from one medium to another
Angle of incidence (i): The angle between the incoming light ray and the normal (a line perpendicular to the surface)
Angle of refraction (r): The angle between the refracted light ray and the normal
Practical tips
Trace the paths of the light rays accurately
Measure angles using a protractor
Measure the angle from the normal (central line)
Light rays entering the block refract away from the normal
At a 90° angle of incidence, the ray does not refract (i = r)
IV. Electricity and magnetism
Relationship between Voltage and Current
The relationship between voltage and current is expressed through Ohm’s Law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points.
Key concepts
Ohm’s Law can be written in three ways: • I = V/R • V = IR • R = V/I
Potential difference (simply known as voltage) is the work done per unit charge to move a charge between two points in an electric field
Voltage and current behave differently in series and parallel circuits. • Series circuit: the current is the same throughout, while the voltage is divided across the components • Parallel circuit: the voltage is the same across each branch, while the current is divided
A rheostat, or variable resistor, is used to change the resistance in the circuit so the experimenter can observe the corresponding changes in voltage and current
Practical tips
Learn the standardised symbols for electrical circuits
The ammeter has to be connected in series with the resistor to measure the current flowing through it
The voltmeter has to be connected in parallel with the resistor to measure the voltage across it
Check the metres for zero error and adjust for it while taking measurements
If using a fixed resistor, the graph should be a straight line passing through the origin. The slope of the graph represents the resistance (R)
Use a low-voltage power supply and handle with care to avoid electric shock
Disconnect the circuit when not taking readings to prevent overheating
Use of Resistance Wire
Key concepts
The resistance of a wire depends on its length (L), thickness/cross-sectional area (A), and resistivity of the material (ρ)
Resistance (R) is the opposition to the flow of electric current, measured in ohms (Ω) • Higher resistance means less current will flow for a given voltage
For most conductors, resistance increases with temperature
Formula for Resistance: R = ρL / A
Practical tips
Connect the ammeter in series with the resistance wire to measure the current flowing through it
Connect the voltmeter in parallel across the wire to measure the voltage across it
Measure the length of the wire between the clips
Use suitable apparatus, such as a micrometre screw gauge, to measure the diameter of the wire
Avoid excessive current as it may heat the wire and alter its resistance
Use straight, uncoiled wires
Use of Light Dependent Resistor
Light-dependent resistors (LDR) are a type of resistor (or photoresistors) whose resistance changes with light intensity.
Key concepts
The ability of a material to change its electrical conductivity when exposed to light is known as photoconductivity
LDRs have resistance variation: high resistance in darkness and low resistance in bright light
LDRs have a response time to changes in light intensity. Observe how some are more sensitive to changes in light intensity than others.
Practical tips
Experiment in a dark room to minimise the possibility of ambient light interfering with results
Ensure that the circuits are connected properly
A typical circuit setup usually has an LDR connected in series with a fixed resistor and a voltmeter to measure the voltage
Position the light source at a fixed distance from the LDR for consistency
The graph should show a decreasing trend, indicating that resistance decreases as light intensity increases
Motor experiments
The motor effect can be used to create a simple direct current electric motor by placing coils of wires (or solenoids) into a magnetic field.
Key concepts
Fleming's Left-Hand Rule: This rule helps you determine the direction of the force on a current-carrying conductor in a magnetic field • First finger = Field • seCond finger = Current • thuMb = Motion/Force
Formula for Force: F (force) = BIL • B (magnetic field strength) • I (current) • L (length of the conductor in the field)
Magnetic fields have direction. The interaction between the magnetic fields of the coil and the magnets results in a force applied to the coil, causing it to rotate
Reversing the direction of the current or the magnetic field will reverse the direction of the force on the coil
Practical tips
Connect the coil to a DC (direct current) power supply with a variable voltage
Ensure the coil is positioned so that the magnetic field lines are perpendicular to the direction of current in the coil to maximise force
Observe the movement of the coil when the current is switched on and use Flemin’s Left-Hand Rule to verify the direction of force on it
Changing the current, strength of the magnetic field, or the number of coils in the wire will affect the force and movement
Securely suspend the coil and magnets to prevent movement during the experiment
Remove other sources of magnetic fields (i.e., electronic devices) to minimise interference
Master Your Physics Practical Exam With Keynote Learning
The final preparation stage lies in consistent practice with past year's papers and applying our list of useful study tips and strategies. Students who are well prepared for these practical questions will be able to excel when faced with the real deal. Be sure to use this guide as a helpful revision checklist while preparing for the Physics practical examination!
Need more support to boost your child’s confidence? Keynote Learning offers Physics tuition classes to help students become exam-ready, through targeted practice and personalised attention to weak areas.
