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A Level Core Practicals

A-Level Physics Practicals

This document covers the core practical procedures across the A-Level Physics course, organized by module

Module 3: Mechanics

1. Investigating Motion and Collisions

Focuses on verifying momentum conservation or investigating the relationship between force and acceleration.

Equipment

  • Trolleys or air track gliders
  • Air track or friction-compensated ramp
  • Light gates and a digital data logger
  • Interrupter cards (of known length)
  • Masses and string (if investigating $F=ma$)

Method & Data Analysis

  1. Set up the air track or ramp. If using a ramp, tilt it slightly to compensate for friction.
  2. Attach an interrupter card to the trolley and set up two light gates.
  3. For a collision, place one trolley at rest and launch the second toward it.
  4. Record initial velocity ($u$) and final velocities ($v$) using light gates.
  5. Measure the mass of each trolley.
  6. Data Analysis: Compare initial momentum ($m_1u_1 + m_2u_2$) to final momentum ($m_1v_1 + m_2v_2$).
  7. Data Analysis: Calculate kinetic energy ($1/2mv^2$) to determine if the collision was elastic.

Improving Accuracy

  • Use an air track to eliminate friction.
  • Ensure interrupter cards are vertical and measured precisely.
  • Repeat measurements and calculate a mean.

Safety

  • Use a "catch box" to stop trolleys falling.
  • Securely attach masses to the string.

2. Determining Acceleration of Free Fall ($g$)

Measuring $g$ using a falling object and electronic timing.

Equipment

  • Electromagnet and steel ball bearing
  • Trapdoor and base unit
  • Electronic timer or data logger
  • Metre ruler and plumb line

Method & Data Analysis

  1. Position the electromagnet at height ($h$) above the trapdoor.
  2. Release the ball; the timer starts on release and stops when the trapdoor is hit.
  3. Repeat for at least five different heights.
  4. Data Analysis: Use $h = 1/2gt^2$ (from $s = ut + 1/2at^2$ where $u=0$).
  5. Data Analysis: Plot $h$ vs $t^2$. Gradient = $g/2$.

Improving Accuracy

  • Use a small, dense ball to minimize air resistance.
  • Measure height from the bottom of the ball to the top of the trapdoor.

Safety

  • Switch off electromagnet when not in use.
  • Keep floor clear of trip hazards.

3. Determining Terminal Velocity in Fluids

Investigating motion when drag force equals weight.

Equipment

  • Large transparent cylinder
  • Viscous liquid (Glycerol or heavy oil)
  • Steel ball bearings (varying sizes)
  • Stopwatch and rubber bands (for markers)

Method & Data Analysis

  1. Mark equal intervals on the cylinder using rubber bands.
  2. Drop the ball bearing into the center.
  3. Record time at each marker; constant time between markers indicates terminal velocity.
  4. Data Analysis: Calculate $v = \Delta s / \Delta t$.
  5. Data Analysis: Plot velocity vs time; the plateau is terminal velocity.

Improving Accuracy

  • Drop in the center to avoid "wall effects."
  • Use a tall enough cylinder to ensure terminal velocity is reached.
  • Use video analysis for more precise timing.

Safety

  • Clean spills immediately (slippery).
  • Wear goggles to prevent splashes.

4. Experimental Determination of Centre of Gravity

Using the principle of moments to locate the balancing point.

Equipment

  • Irregularly shaped flat object (lamina)
  • Plumb line (string and weight)
  • Clamp stand, pin, and pencil

Method & Data Analysis

  1. Make three holes near the edges of the lamina.
  2. Suspend the lamina and plumb line from a pin through one hole.
  3. Mark the path of the plumb line on the lamina.
  4. Repeat for other holes.
  5. Data Analysis: The intersection of the lines is the centre of gravity.

Improving Accuracy

  • Ensure the lamina swings freely.
  • Use a thin, sharp pencil for lines.
  • Space holes widely around the perimeter.

Safety

  • Take care with pins to avoid finger pricks.
  • Secure the clamp stand to the desk.

5. Investigating Force-Extension Characteristics

Applying Hooke’s Law to determine material stiffness.

Equipment

  • Helical spring, rubber band, or polythene strip
  • Clamp stand and slotted masses
  • Millimetre ruler and set square

Method & Data Analysis

  1. Measure original length ($l_0$).
  2. Add masses in increments, recording the new length ($l$).
  3. Calculate extension $x = l - l_0$.
  4. Unload masses to check for plastic deformation.
  5. Data Analysis: Plot Force vs Extension.
  6. Data Analysis: Gradient of linear section is the spring constant ($k$) where $F = kx$.

Improving Accuracy

  • Use a set square to avoid parallax error.
  • Wait for oscillations to stop before reading.

Safety

  • Wear goggles in case the spring snaps.
  • Use a padded box under masses to protect feet.

Module 4: Electrons, Waves, and Photons

6. Determining the Young Modulus

Determining stiffness by measuring the ratio of tensile stress to tensile strain.

Equipment

  • Long, thin metal wire
  • G-clamp, pulley, and slotted masses
  • Micrometer and travelling microscope

Method & Data Analysis

  1. Measure wire diameter in several places to find average area ($A$).
  2. Measure original length ($L$) from clamp to marker.
  3. Add masses and measure extension ($\Delta L$) using a travelling microscope.
  4. Data Analysis: Calculate stress ($\sigma = F/A$) and strain ($\varepsilon = \Delta L/L$).
  5. Data Analysis: Plot Stress vs Strain. Gradient = Young Modulus ($E$).

Improving Accuracy

  • Use a long wire (3m+) for larger extensions.
  • Ensure the wire is straight and free of kinks.

Safety

  • Wear goggles; wire can whip if it snaps.
  • Use a padded box for falling weights.

7. Investigating Electrical Characteristics (I-V)

Examining how current varies with potential difference across components.

Equipment

  • Variable DC power supply or rheostat
  • Ammeter and Voltmeter
  • Components: Resistor, filament lamp, diode, thermistor

Method & Data Analysis

  1. Connect component in series with ammeter and variable resistor.
  2. Connect voltmeter in parallel across the component.
  3. Vary potential difference and record $I$ and $V$.
  4. Reverse connections for negative readings.
  5. Data Analysis: Plot $I$ vs $V$.

Improving Accuracy

  • Use a potential divider for better control at low voltages.
  • Switch off between readings to prevent heating.

Safety

  • Components can become hot; avoid touching during operation.

8. Determining the Resistivity of a Metal

Calculating material-specific property independent of dimensions.

Equipment

  • Resistance wire and micrometer
  • Ammeter, Voltmeter, and metre ruler
  • Jockey or crocodile clips

Method & Data Analysis

  1. Measure wire diameter to find area ($A$).
  2. Vary the length ($L$) of wire in the circuit.
  3. Record Resistance ($R = V/I$) for each length.
  4. Data Analysis: Plot $R$ vs $L$. Gradient = $\rho/A$.
  5. Data Analysis: $\rho = \text{gradient} \times A$.

Improving Accuracy

  • Pull wire taut against the ruler.
  • Use low current to minimize heating.

Safety

  • Wire can become very hot; do not touch while power is on.

9. Determining Internal Resistance

Investigating terminal voltage drop under load.

Equipment

  • Cell, variable resistor, and switch
  • Ammeter and Voltmeter

Method & Data Analysis

  1. Record e.m.f. ($\varepsilon$) with switch open ($I=0$).
  2. Close switch and vary current ($I$) using the variable resistor.
  3. Record terminal voltage ($V$) and $I$.
  4. Data Analysis: Use $V = \varepsilon - Ir$.
  5. Data Analysis: Plot $V$ vs $I$. y-intercept = $\varepsilon$, magnitude of gradient = $r$.

Improving Accuracy

  • Use a new battery for stable readings.
  • Close switch only briefly for each reading.

Safety

  • Avoid short circuits to prevent cell damage or leaks.

10. Investigating Potential Divider Circuits

Creating specific output voltages using resistor combinations.

Equipment

  • Power supply, fixed resistors
  • Thermistor or LDR
  • Voltmeter, water bath/lamp

Method & Data Analysis

  1. Set up two components in series.
  2. Measure $V_{out}$ across one component.
  3. Vary temperature (thermistor) or light (LDR).
  4. Data Analysis: Compare to $V_{out} = V_{in} \times (R_2 / (R_1 + R_2))$.

Improving Accuracy

  • Keep thermometer and thermistor close together.
  • Measure distance to light source for LDR.

Safety

  • Keep water away from power supplies.

11. Using an Oscilloscope to Determine Frequency

Measuring time periods to calculate wave frequency.

Equipment

  • Oscilloscope (CRO)
  • Signal generator

Method & Data Analysis

  1. Connect signal generator to CRO.
  2. Adjust Time-base to see at least one full cycle.
  3. Measure horizontal divisions for one cycle.
  4. Calculate Period ($T$) = divisions $\times$ Time-base.
  5. Data Analysis: Frequency $f = 1/T$.

Improving Accuracy

  • Measure across multiple cycles and divide.
  • Align cycle start with a major grid line.

Safety

  • Ensure equipment is PAT tested.

12. Demonstrating Wave Effects in a Ripple Tank

Visualizing reflection, refraction, and diffraction.

Equipment

  • Ripple tank, motor-driven dipper
  • Strobe light
  • Barriers and glass blocks

Method & Data Analysis

  1. Set up shallow water and constant dipper frequency.
  2. Use strobe to "freeze" waves.
  3. Use barriers for reflection/diffraction and glass blocks for refraction.
  4. Data Analysis: Measure $\lambda$; calculate $v = f\lambda$.

Improving Accuracy

  • Use a strobe for stable measurements.
  • Ensure tank is level and on a damped surface.

Safety

  • Keep water away from electricity.
  • Be aware of strobe sensitivity (epilepsy).

13. Observing Polarising Effects

Demonstrating transverse wave planes.

Equipment

  • Microwave transmitter/receiver and metal grille
  • Light source and polarising filters

Method & Data Analysis

  1. Light: Rotate one filter relative to another; observe intensity changes.
  2. Microwaves: Rotate metal grille between transmitter and receiver.
  3. Data Analysis: Note absorption when wires are parallel to electric field oscillation.

Improving Accuracy

  • Use a digital light sensor.
  • Keep metal objects away from microwave path.

Safety

  • Do not look directly at high-intensity light.

14. Investigating Refraction and Total Internal Reflection

Mapping light paths across media boundaries.

Equipment

  • Ray box, glass blocks (rectangular and semi-circular)
  • Protractor and paper

Method & Data Analysis

  1. Trace block outline and entry/exit rays.
  2. Measure angles of incidence ($i$) and refraction ($r$).
  3. For TIR, use semi-circular block and increase $i$ until refraction disappears.
  4. Data Analysis: Plot $\sin i$ vs $\sin r$. Gradient = $n$.
  5. Data Analysis: Verify $n = 1 / \sin C$.

Improving Accuracy

  • Use a thin ray and sharp pencil.
  • Use a large protractor.

Safety

  • Ray boxes get hot; turn off when not in use.

15. Superposition Experiments

Investigating interference patterns from coherent sources.

Equipment

  • Two speakers/Laser/Microwaves
  • Double-slit slide and screen

Method & Data Analysis

  1. Shine laser through double-slit.
  2. Measure slit separation ($d$), distance to screen ($D$), and fringe width ($w$).
  3. Data Analysis: $\lambda = \frac{dw}{D}$.

Improving Accuracy

  • Ensure $D$ is large ($2\text{m}+$).
  • Measure across several fringes and divide.

Safety

  • Laser Safety: Never look directly into the beam.

16. Determining the Wavelength of Light

Using diffraction to measure nanometer-scale wavelengths.

Equipment

  • Laser, diffraction grating
  • Metre ruler and tape measure

Method & Data Analysis

  1. Shine laser through grating onto screen.
  2. Measure distance to screen ($D$) and distance to maxima ($x$).
  3. Calculate slit separation $d$ from lines per mm.
  4. Data Analysis: Use $d \sin \theta = n\lambda$ where $\tan \theta = x/D$.

Improving Accuracy

  • Large $D$ reduces percentage uncertainty.
  • Measure between orders (e.g., $+1$ to $-1$) and divide.

Safety

  • Standard laser safety protocols.

17. Observing Stationary Waves

Demonstrating interference forming nodes and antinodes.

Equipment

  • Vibration generator, signal generator
  • String, pulley, and weights

Method & Data Analysis

  1. Vary frequency until a standing wave forms.
  2. Find harmonics.
  3. Data Analysis: Node-to-node distance = $\lambda/2$.
  4. Data Analysis: Calculate $v = f\lambda$.

Improving Accuracy

  • Use a sharp bridge for the fixed end.
  • Repeat for multiple harmonics.

Safety

  • Wear goggles in case the string snaps.

18. Determining the Speed of Sound in Air

Using resonance in a closed pipe.

Equipment

  • Resonance tube, cylinder of water
  • Tuning forks, metre ruler

Method & Data Analysis

  1. Hold vibrating fork over tube and raise from water until resonance.
  2. Measure air column length ($L$).
  3. Data Analysis: First resonance $L + c = v/4f$ ($c$ is end correction).
  4. Data Analysis: Plot $L$ vs $1/f$. Gradient = $v/4$.

Improving Accuracy

  • Average length from raising and lowering.
  • Perform end correction.

Safety

  • Mop up water spills.

19. Determining the Planck Constant ($h$)

Using LED "turn-on" voltage.

Equipment

  • LEDs of different wavelengths
  • Power supply, voltmeter, resistor

Method & Data Analysis

  1. Increase voltage until LED just glows; record threshold $V_0$.
  2. Repeat for different colors.
  3. Data Analysis: $eV_0 = hc/\lambda$.
  4. Data Analysis: Plot $V_0$ vs $1/\lambda$. Gradient = $hc/e$.

Improving Accuracy

  • Use a dark room to see initial glow.
  • Extrapolate $I-V$ graph to $I=0$.

Safety

  • Do not exceed LED current rating.

20. Demonstration of the Photoelectric Effect

Evidence for light as a particle.

Equipment

  • Gold-leaf electroscope, zinc plate
  • UV lamp, emery paper

Method & Data Analysis

  1. Clean zinc plate and place on negatively charged electroscope.
  2. Shine UV; leaf falls as electrons emit.
  3. Repeat with glass (absorbs UV) or positive charge (no emission).
  4. Data Analysis: $hf = \Phi + KE_{max}$.

Improving Accuracy

  • Ensure zinc is freshly sanded.
  • Use a dry room.

Safety

  • UV Safety: Wear UV-filtering goggles; do not look at lamp.

Module 5: Newtonian World and Astrophysics

21. Experimental Evidence of Electron Diffraction

Demonstrating wave-like nature of electrons.

Equipment

  • Electron diffraction tube
  • EHT power supply

Method & Data Analysis

  1. Accelerate electrons through graphite target.
  2. Measure diffraction ring diameters ($D$) on screen.
  3. Data Analysis: Calculate $\lambda = \frac{h}{\sqrt{2meV}}$.
  4. Data Analysis: Verify with $n\lambda = d \sin \theta$.

Improving Accuracy

  • Darkened room for visibility.
  • Measure at multiple voltages.

Safety

  • High Voltage: Do not touch terminals.
  • Fragile Vacuum: Handle tube with care.

22. Observing Brownian Motion

Evidence for kinetic theory of gases.

Equipment

  • Smoke cell, microscope, lamp

Method & Data Analysis

  1. Seal smoke in cell and illuminate from side.
  2. Observe random, jerky motion under microscope.
  3. Data Analysis: Conclude bombardment by invisible air molecules.

Improving Accuracy

  • Ensure cell is airtight.
  • Let lamp warm up to avoid convection.

Safety

  • Use matches/smoke in ventilated area.

23. Determining Specific Heat Capacity

Measuring energy to raise material temperature.

Equipment

  • Metal block, immersion heater, thermometer
  • Ammeter, Voltmeter, Stopwatch, Insulation

Method & Data Analysis

  1. Measure mass ($m$) and insulate block.
  2. Record Temperature vs Time while heating.
  3. Data Analysis: $E = VIt$.
  4. Data Analysis: $P = mc \times (\Delta \theta / \Delta t)$.

Improving Accuracy

  • Use oil in holes for thermal contact.
  • Measure max temperature after heater is off.

Safety

  • Heater gets very hot; use only when submerged.

24. Determining Specific Latent Heat

Energy for change of state at constant temperature.

Equipment

  • Ice/Water, immersion heaters, balances

Method & Data Analysis

  1. Use a "test" and "control" setup for melting ice.
  2. Measure mass melted by heater ($m = m_{test} - m_{control}$).
  3. Data Analysis: $L_f = VIt / m$.

Improving Accuracy

  • Ensure ice is at $0\text{°C}$.
  • Steady boil for vaporisation.

Safety

  • Avoid steam burns and keep water from electronics.

25. Investigating Gas Laws

Exploring P, V, and T relationships.

Equipment

  • Boyle’s Law apparatus, constant volume bulb
  • Pressure gauge, water bath

Method & Data Analysis

  1. Boyle: Plot $P$ vs $1/V$.
  2. Pressure: Plot $P$ vs $T$ (Celsius); extrapolate to $P=0$ for absolute zero.

Improving Accuracy

  • Change volume slowly (isothermal).
  • Submerge entire gas volume in water bath.

Safety

  • Do not exceed pressure limits.

26. Investigating Circular Motion

Relationship between force, mass, velocity, and radius.

Equipment

  • Rubber bung, tube, string, masses
  • Stopwatch, balance, ruler

Method & Data Analysis

  1. Whirl bung in horizontal circle with hanging mass providing centripetal force ($F=Mg$).
  2. Maintain constant radius ($r$) and record time for 20 rotations.
  3. Data Analysis: Calculate $v = 2\pi r / T$.
  4. Data Analysis: Plot $F$ vs $v^2$. Gradient = $m/r$.

Improving Accuracy

  • Use slow-motion camera for rotations.
  • Whirl as horizontally as possible.

Safety

  • Clear "no-go" zone for swinging bung.
  • Wear goggles.

27. Determining Period/Frequency of SHM

Factors affecting oscillating systems.

Equipment

  • Masses, spring or pendulum
  • Stopwatch, fiducial marker

Method & Data Analysis

  1. Displace mass and record time for 20 oscillations.
  2. Vary mass (spring) or length (pendulum).
  3. Data Analysis (Spring): Plot $T^2$ vs $m$. Gradient = $4\pi^2/k$.
  4. Data Analysis (Pendulum): Plot $T^2$ vs $L$. Gradient = $4\pi^2/g$.

Improving Accuracy

  • Use fiducial marker at equilibrium.
  • Small angles ($<10^\circ$) for pendulum.

Safety

  • Padded catch box for falling masses.

Module 6: Particles and Medical Physics

28. Investigating Capacitors in Combination

Verifying series and parallel rules.

Equipment

  • Capacitors, multimeters

Method & Data Analysis

  1. Measure $C_{total}$ for series and parallel arrangements.
  2. Data Analysis: Parallel $C_{total} = \sum C$; Series $1/C_{total} = \sum 1/C$.

Improving Accuracy

  • Account for zero error of meter.

Safety

  • Check polarity of electrolytic capacitors.

29. Investigating Capacitor Charge and Discharge

Exponential decay of voltage/current.

Equipment

  • Capacitor, resistor, DC source, stopwatch

Method & Data Analysis

  1. Charge capacitor then discharge through resistor.
  2. Record $V$ vs time.
  3. Data Analysis: Plot $\ln V$ vs $t$. Gradient = $-1/RC$.
  4. Data Analysis: Time constant $\tau$ is time to fall to $37%$.

Improving Accuracy

  • Use high-resistance voltmeter.

Safety

  • Capacitors store energy; discharge safely.

30. Determining Magnetic Flux Density ($B$)

Using a current balance to measure force.

Equipment

  • Magnets, top-pan balance, stiff wire
  • Power supply, ammeter

Method & Data Analysis

  1. Place magnets on balance and tare.
  2. Run current through wire between magnets.
  3. Record mass change ($\Delta m$) for different currents ($I$).
  4. Data Analysis: $F = \Delta mg$. Plot $F$ vs $I$. Gradient = $BL$.

Improving Accuracy

  • Wire must be perfectly perpendicular to field.
  • Use high-precision balance.

Safety

  • Strong magnets (keep away from cards/pacemakers).

31. Investigating Magnetic Flux with Search Coils

Mapping field strength and orientation.

Equipment

  • Search coil, solenoid, signal generator, CRO

Method & Data Analysis

  1. Place search coil in solenoid with AC field.
  2. Record induced e.m.f. ($V_0$).
  3. Vary angle ($\theta$) or position.
  4. Data Analysis: $V_0 \propto BAN\omega$.

Improving Accuracy

  • High frequency for larger e.m.f.
  • Keep away from other metal objects.

Safety

  • Do not let solenoid overheat.

32. Investigating Transformers

Turn ratios and voltage relationships.

Equipment

  • C-cores, copper wire, AC supply, voltmeters

Method & Data Analysis

  1. Wrap primary and secondary coils on C-cores.
  2. Measure $V_p$ and $V_s$ for different $N_s$.
  3. Data Analysis: $\frac{V_s}{V_p} = \frac{N_s}{N_p}$.

Improving Accuracy

  • Clamp cores tightly.
  • Laminated cores reduce losses.

Safety

  • Low Voltage AC Only.

33. Absorption of Alpha, Beta, and Gamma Radiation

Testing penetrating power.

Equipment

  • Sources, G-M tube and counter
  • Absorbers: Paper, Aluminum, Lead

Method & Data Analysis

  1. Measure background count.
  2. Measure count rate with source and different absorbers.
  3. Data Analysis: Use corrected count rate (Total - Background).

Improving Accuracy

  • Long counting times.
  • Constant source-tube distance.

Safety

  • Time, Distance, Shielding. Use forceps.

34. Determining the Half-Life of an Isotope

Measuring decay rate over time.

Equipment

  • Protactinium generator, G-M tube, data logger

Method & Data Analysis

  1. Shake generator and record count rate every 10s.
  2. Data Analysis: Plot corrected count rate vs time.
  3. Data Analysis: Find time to halve ($t_{1/2}$). Or plot $\ln(\text{Count Rate})$ vs $t$; gradient = $-\lambda$.

Improving Accuracy

  • Start readings immediately after shaking.

Safety

  • Sealed source but handle with care.

35. Simulation of Radioactive Decay

Statistical model using dice.

Equipment

  • Large number of dice

Method & Data Analysis

  1. Roll dice and remove those showing a "6".
  2. Record remaining dice ($N$) vs throw number ($t$).
  3. Data Analysis: Plot $N$ vs $t$ for exponential curve.
  4. Data Analysis: Verify $\lambda = 1/6$.

Improving Accuracy

  • Use large starting number (500+).

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