We were recently hired to produce a series of animation clips for Science Photo Library, showing how various things work. Here are our favourite 8!
Clip 1 ) Catalytic converter. It consists of a honeycomb structure, which provides a large surface area. The inside surface is lined with the catalyst, which is a combination of rhodium (Rh) and platinum (Pt) metals. On the rhodium, nitrogen oxides (nitric oxide, NO, shown here) are reduced to nitrogen and oxygen. On the platinum, carbon monoxide (CO) reacts with oxygen to form carbon dioxide;
Clip 2 ) Fuel cell. Hydrogen is introduced at the anode side, and oxygen at the cathode. A catalyst splits the hydrogen into two protons and electrons. The membrane allows the protons through to the cathode, but forces the electrons down a wire. The flow of electrons through the wire can perform electrical work. On the cathode side, the protons and electrons react with an oxygen atom, forming water;
Clip 3 ) Photocopier. Inside the machine is a rotating drum covered in a photoconductive material. The drum is charged by a corona wire (also covered in +). A bright light is used to illuminate the paper to be copied. The light is reflected via a system of mirrors to the charged drum. The photoconductive coating becomes conductive when exposed to light, so the bright, reflective regions of the paper cause the drum surface to discharge in the same pattern. A toner (negatively charged) is then applied to the drum, and is attracted to the positively charged regions, forming a toner pattern identical to the original. A blank sheet of paper is then charged and is passed under the drum, transferring the toner to the paper, reproducing the initial image;
Clip 4 ) Electron Microscope. An electron gun at the top of the column produces a beam of fast-moving electrons. These are focused by magnetic lenses , which deflect the negatively-charged electrons. A sample is introduced into the beam, absorbing and interacting with some electrons, and the remainder are focused onto a screen at the bottom;
Clip 5 ) PET scanner. The patient ingests the fluorodeoxyglucose, a radioactive tracer, and it spreads throughout the body like normal glucose, being absorbed by more active tissues, including tumours. However, the chemical has been designed to contain a radioactive 18-F fluorine atom in place of one of the normal hydroxide groups. When it decays, it emits a positron (red), which quickly collides with an electron (blue), leading to the annihilation of both, and the emission of two gamma rays (yellow) in opposite directions. The PET scanner detects these gamma rays, and uses them to locate tissues with a high glucose uptake, as seen on the screen;
Clip 6 ) Nuclear reactor. This is a pressurised water reactor, the most common type in operation. At the heat of the reactor is the core, which contains the nuclear fuel, uranium. When a neutron (yellow) hits a U-235 nucleus, it undergoes fission (left inset), releasing three more neutrons. Initially these neutrons are very fast, reducing the chances that they’ll fission another U-235 atom. However, the reactor core contains water under high pressure. Water acts as a neutron moderator (central inset), slowing it down and increasing its chances of fissioning another U-235 (right inset). This process continues in a chain reaction, producing a large amount of heat. To help control the rate of the reaction, control rods can be raised or lowered into the core. These contain boron-10 (inset), which has a high neutron absorption capability, reducing the number of neutrons available for fission. Outside the core, the hot water from the reactor (orange) is passed into a secondary water system in heat-exchanging pipes. This converts the cool water (blue) into steam (red), which drives a conventional electricity generating turbine, which sends power out to the grid;
Clip 7 ) Loudspeaker. Inside the loudspeaker is a magnet, with the south pole surrounded by a coil of wire attached to a paper cone. When the wire carries a current, I, it induces a magnetic field around the wire. This interacts with the field of the magnet, producing a force that moves the coil. The direction of the movement can be predicted using a left-hand rule, demonstrated at bottom left. This moves the coil and its attached cone, which generates sound waves. Controlling the varying current flowing in the wire therefore controls the vibration of the cone, and hence the sound it produces;
Clip 8 ) CD player. Animation showing how the tracks of microscopic bumps on a CD’s surface are used to encode digital data. If you compare a reference beam and the data beam, you can see that a change in the surface causes constructive or destructive interference with the outgoing beam, and so the changes in topology can be detected. A change in the surface topology is registered as a 1 and no change is registered as a 0.
Science Photo Library provides licensing of striking specialist science imagery, with more than 350,000 images and 20,000 clips.
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