02Particle
Something has to push it
An electric field does work on the charge. Inside a radio frequency cavity the field flips in step with the particle, so every gap it crosses adds energy instead of taking it back.
E FIELDdoes work on the charge
One electron.Two worlds.One story.
Accelerated at CERN, drifting through copper, landing on phosphor: one particle, followed the whole way.
Interactive guide · for the curious of every age
03Particle
Kilometres of machine, for one particle
The hardware repeats: vacuum pipe, cavity, magnet, cavity, magnet. That rhythm is what the scale is made of, and the electron passes all of it in a fraction of a second.
≈ 27 kmcircumference of the largest ring at CERN
04Particle
A magnetic field steers, it does not speed up
The force is always at right angles to the motion, so it bends the path and leaves the energy untouched. Everything about where the particle goes is decided here.
B FIELDbends the path, adds no energy
05Particle
Hold on to the particle. Change everything else.
The machine falls away and its repeating structure reassembles at a scale a hundred billion times smaller. The rings become copper ions. The electron has not moved.
same particledifferent world
06Current
A wire is not empty
Copper carries a sea of electrons that belong to no single atom. Switching on a field does not create them. It only gives their motion a direction.
8.5 × 10²⁸ m⁻³conduction electrons in copper
07Current
The electrons barely move
Thermal motion is violent, random and goes nowhere. On top of it the field adds a drift so slow that you could walk the length of a cable faster than the charge inside it.
≈ 0.1 mm/sdrift velocity in a household wire
08Current
The energy does not wait
The lamp lights the instant you press the switch, because what travels is the electromagnetic field around the conductor, not the charge inside it.
≈ 2 × 10⁸ m/sspeed of the energy front
09Current
Now reverse it, a hundred times a second
With alternating current the electrons stop advancing and oscillate about a fixed point. The field around the wire builds, collapses, and builds again the other way.
50 Hzthe direction reverses 100 times a second
10Current
Sweep it sideways and it becomes a signal
Deflect the same oscillation across a screen at a steady rate and time becomes a horizontal axis. The shape that appears is not decoration, it is the voltage.
64 µsone line of a 625 line picture
11Current
Analogue is a shape. Digital is a number.
Measure the same curve at fixed instants, round each measurement to the nearest level, and the picture becomes a stream of values that can be copied without loss.
8 bit256 levels per sample
12Beam
The signal has somewhere to go
Behind the glass there is a vacuum, a gun and a coil. A picture tube is a particle accelerator that fits in a living room, and it was built by the million.
≈ 25 kVfinal anode voltage
13Beam
Heat a metal until it lets go
A cathode at eight hundred degrees releases electrons, a grid decides how many get through, and a stack of electrodes at rising potential gathers the rest into a beam.
≈ 800 °Ccathode temperature
14Beam
The same trick, one room away
Coils around the neck make a magnetic field that sweeps the beam across the screen and down it. Nothing mechanical moves. The picture is drawn by a field.
15 625 Hzline frequency of a 625 line system
15Image
The electron becomes light
It arrives carrying the energy of twenty five thousand volts, hands it to a phosphor crystal, and the crystal gives a fraction of it back as light. That is the whole picture, one impact at a time.
a few mshow long the phosphor keeps glowing
16Image
The scale changes. The physics stays the same.
Charge, an electric field to give it energy, a magnetic field to steer it, and a screen to stop it. Twenty seven kilometres or forty centimetres, the list does not get longer.
27 km → 40 cmthe same four steps
Laboratory
Interactive modules
Go deeper, hands-on simulations and clear explanations.
- 01Accelerator basicsSee how electrons are produced and accelerated in particle accelerators.Open module →
- 02The flow of currentTrace the motion of electrons in the circuits that power everyday devices.Open module →
- 03Inside the picture tubeThe electron gun, deflection coils and the image scanning process.Open module →
- 04Waveforms and signalsUnderstand the video signal and how information rides a carrier wave.Open module →
- 05Analog versus digitalCompare a continuous signal with a stream of bits and see the difference.Open module →
- 06From antenna to imageThe TV signal's path, from waves in the air to pixels on screen.Open module →