Practice

 

With the Exams so near now, all there is time for is Practice, Practice, Practice

Ethanol Fuel Cell

 Using an ethanol fuel cell to power led lights and a fan. Fuel cells can be of several different types and comparing them gives the students some idea of how they could be used in the real world.

ATP

What makes ATP, ADP, and AMP so valuable? They are used in DNA and RNA to store and release energy and as signals inside cells. Each day, we recycle kg of these to keep us alive.
 

Iron Ore Extraction

 Very small-scale extraction of ores. On a wooden spill with iron oxide Fe(III)O and some Sodium Carbonate, and place in a Bunsen Burner. The iron oxide is not magnetic, but the iron produced at the end is magnetic, and the filings can be collected and moved by a magnet.

Momentum inline and stacked

 Inelastic collisions comparing one @pascoscientific smartcart hitting two stacked and two inline. Does it make a difference? Not much since the wheels are nearly frictionless. But it is an interesting experiment to do.

Circle Theorems

Students remember all the Circle Theorems so that they can solve the A-level problems. Finding the Midpoint of a chord, then finding a perpendicular and another perpendicular, allows the student to find the centre of the circle.
 

Cathode Ray Tube

 Taking a good look at the insides of an oscilloscope to discover how a Cathode Ray Tube works. Once commonplace, now students don't know what it is, and the technology about how it works, and its history in the discovery of particles.

Practising Serial Dilutions

 Practising Serial dilutions as part of an A-Level Experiment Practice. Some of the students have to do practical experiments, and it is essential to get them to practice the sorts of things they will be doing.

Turing Tumble

Using the Turing Tumble by @UpperStoryCo, the students worked out some assembly language and followed the logic of what was happening to the bits. Using the ball bearings, the students saw how the gates set bits, so they could try adding some bits together and check whether they got the correct answer.

 

Chemistry Mechanisms

 A-Level  Chemistry learning mechanisms of chemical reactions. This is the reaction of Bromine with Propene. We need to draw the curly arrows from the bond to the atom, from the Pi Bond to the Bromine and from the Bromine-Bromine bond to the far Bromine atom.

Model Eye

 Learning how the eye works using the @pascoscientific demo eye and a light source.First, the students experiment with the variable lens, discovering how the lens's shape can be altered by adding or removing water. They then place this into the eye to obtain a sharp image on the retina.

Learning Formulae

 The Easter Holidays are for practising lots of exam questions and discovering that, in addition to the formulae on the exam sheet, there are loads of formulae that you are not given and have to memorise.

Coulombs Law

Coulomb's Law, A Level Physics, measuring the force between two charged polystyrene spheres. Given lots of different equipment and access to the Internet, students had to come up with ways to measure the force between the two spheres. 

 

Measuring Invisible Forces: Coulomb’s Law in the A-Level Physics Lab

If you’ve ever rubbed a balloon on your jumper and stuck it to the wall, congratulations—you’ve seen Coulomb’s Law in action (albeit in a slightly chaotic way).

But how do we go from balloon static to the precise mathematical description of electric forces between charges?

Let’s explore Coulomb’s Law, how students can research it, and—most excitingly—how it can be measured in the A-level Physics laboratory with some clever kit and a steady hand.

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🧲 What is Coulomb’s Law?

Coulomb’s Law describes the electrostatic force between two point charges. In simple terms:

Like charges repel, unlike charges attract—and the strength of that force depends on the size of the charges and how far apart they are.

Mathematically, it’s written as:

$$F = k \frac{|q_1 q_2|}{r^2}$$

Where:

• $F$ is the electrostatic force between the charges,

• $q_1$ and $q_2$ are the magnitudes of the two charges (in Coulombs),

• $r$ is the distance between the centres of the charges (in metres),

• $k$ is Coulomb’s constant ($8.99 \times 10^9 \, \text{Nm}^2/\text{C}^2$).

Notice the inverse square law: if you double the distance between charges, the force drops by a factor of four.

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🔍 Researching Coulomb’s Law

Students preparing to study or demonstrate Coulomb’s Law can approach the research in three main ways:

1. Theoretical Background

Start with a textbook or a reliable online source (like Physics Classroom, HyperPhysics, or Khan Academy). Look for:

• The historical context (Charles-Augustin de Coulomb’s torsion balance in 1785),

• The equation and what each term means,

• How electric field and force relate to charge and distance.

2. Simulations

Interactive tools like the PhET “Electric Forces and Fields” simulator allow students to change charges and distances and see the force vectors in real time. This helps visualise the law in action before touching any lab equipment.

3. Historical Experiments

Research the torsion balance Coulomb used. It’s a delicate device with a bar suspended by a fibre, showing the torque created by repulsive or attractive electric forces. Most school labs don’t have one, but understanding it helps grasp how Coulomb verified the law.

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🧪 Measuring Coulomb’s Law in the Lab

This is where theory meets experiment—and it’s a challenge because electrostatic forces are small and sensitive to environmental interference (like moisture in the air or your hand waving nearby).

Here are a few methods suitable for A-level:

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Method 1: Using a Modern Coulomb Torsion Balance Kit

Some A-level labs are equipped with a Pasco Coulomb’s Law apparatus or similar kits. These often contain:

• A torsion balance with a lightweight conducting sphere,

• A second charged sphere brought near to interact electrostatically,

• A scale or angular measurement to track the force,

• A way to measure distance between charges.

Students follow a method like:

1. Charge the spheres (using a Van de Graaff generator or charging rod),

2. Measure the angle of twist in the torsion wire (proportional to force),

3. Measure distance between charges,

4. Repeat with different distances and/or charge magnitudes.

Plotting $F$ against $1/r^2$ should give a straight line, proving the inverse-square relationship.

✅ Top Tip: Do this in a dry room with minimal air currents. Keep mobile phones away.

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Method 2: Parallel Plate Repulsion

If a torsion balance isn’t available, students can try a basic version using:

• Two lightweight foil disks or spheres on insulating threads,

• A known charge transferred by rubbing or induction,

• A ruler or protractor to measure repulsion distance.

While not precise, it demonstrates the principle qualitatively. A graph of repulsion distance versus applied charge gives students a sense of the relationship between force and charge.

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Method 3: Use a Top Pan Balance

If equipment is limited, assess understanding using simulations where:

• Students set up charges and vary the distance,

• One sphere is placed on a balance and the other is suspended above and moved down. The change in Mass is recorded.

• Plot force vs distance graphs and analyse gradients.

Whilst this method is not precise, the students can see the force changing, and if they can work out the charge on the sphere using some type of charge meter, then this will work.

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📊 Analysing Results

After collecting data:

• Plot $F$ vs $1/r^2$ – the graph should be linear if Coulomb’s Law holds.

• Use the gradient to calculate $k$, and compare with the theoretical value.

• Discuss sources of error: inconsistent charging, movement of air, inaccurate distance readings, etc.

Extension for keen students: Try to calculate the charge on one of the spheres by rearranging Coulomb’s Law. This introduces the idea of using experimental data to estimate charge—a great link to later studies in fields and electronics.

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🧠 Final Thoughts

Coulomb’s Law is one of those elegant physics laws: deceptively simple, yet deeply powerful. It’s the electric version of Newton’s Law of Gravitation—and just as fundamental to our understanding of the universe.

By researching the theory, experimenting carefully, and analysing results critically, A-level students not only grasp the concepts—they develop the skills of real scientists.

Learning to use a simple microtome

 

We took a slice of a transverse section through a rosemary leaf using a microtome and a cut-throat razor, taking ever-thinner slices until we could get one that was about one cell thick. This was then stained and placed on a microscope slide with a cover slip.

Did I forget something?

 A level psychology Someone walks upstairs and having got there can’t remember why they walked up the stairs does forgetting get worse with old age or is it due to the way we learn?

Computer Projects

 It is that time of year when the year 12 students need to start thinking about A-level Computing Projects. The first step is to think of a project that can fulfil the exam criteria to gain the maximum potential marks.

pH Curve

 Chemistry GCSE: I needed a pH curve for revision to show the students. With the @pascoscientific drop counter, a pH probe, and a temperature probe - 2 experiments in one, with some Potassium Hydroxide in a beaker and some HCl delivered by the drop counter, we had the pH Curve and all the data to go with it.

Damped oscillations

 Investigating Damping using a @Pascoscientific smartcart as a pendulum. Having the smartcart on a track at a steep angle with a spring. Changing the spring constant by changing the spring and adding air resistance created light, heavy and critical damping

Primary Socialisation

 A level Sociology Education is the key to learning how to behave in society. Some sociologists argue that cultural factors are the main explanation for differences in educational achievement. Differences in primary socialisation may mean that some groups find it easier to engage with the culture of the school.

Eclipse

 In Physics, we explore why eclipses don’t happen every month — despite regular new and full moons. We also look at how the Moon’s changing distance from Earth creates different types of eclipses and how this is all controlled by gravity and angular momentum..

Capillary Rise

 How does transpiration work, and how does capillary rise help the plants? We investigated the bores of different-sized capillary tubes to find out the effects of having smaller bores.  The smaller the bore, the higher the rise. Next, to measure the size of the xylem cells. 

Building Computer Race

Practice is over. The teams are set. All have the same hardware to assemble, the motherboard, processor, RAM, Graphics card and USB Board, but who can assemble the parts, install the Operating system and hook up to the network the fastest.

Making Butanoic Acid

 Making Butanoic Acid from Butanol by refluxing with acidified Potassium Dichromate and then distilling the Acid into a conical flask for later experimentation. Getting students to learn skills by building the apparatus from scratch and discovering all about ground glass joint laboratory equipment.

Circuit emulation

 Setting up circuits in @pascoscientific Capstone, to emulate different electric circuits. Faster than building the circuits for electricity revision, the emulators can calculate the resistances, current and voltages.

Looks like Maths

Many of us have a compartmentalised brain—Chemistry is Chemistry, and Maths is Maths. When students find an easy Maths problem in Chemistry, it is suddenly more difficult because they perceive it as the wrong subject.

Measuring the Speed of Sound

 Measuring the speed of Sound using a tuning fork and a tube, pulling out the slider until the loudest sound can be heard and measuring the distance from the tuning fork. This gives the wavelength. Repeat this several times to get a good average, and then work out how much of a wavelength the distance is calculated at the velocity of sound in air at this temperature.