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ELECTRONIC/COMPUTER AGE Electronic/Computer Age Electronics – Electrical signals can carry information quickly over wires or through the air by radio – Light, Appliances and Entertainment Atoms – An atom is the tiniest part of a material – There are only 109 elements known to exist – Compounds --- different kinds of atoms combined together, e.g. table salt, water etc – A compound has properties all its own – Atoms are made of smaller particles with their own properties – Protons and neutrons in the nucleus and electrons in the orbits circling the nucleus --- protons and electrons have diff. charges Electronic/Computer Age Electric Current – Materials whose atoms give up some electrons easily are conductors – Materials that hold tightly to their electrons are insulators – The flow of electrons is current --- Amperes – 1 amp = 6 billion billion electrons flowing past a point in 1 sec – Electromotive force makes a current flow --- Volts – A battery provides electromotive force – Resistance is the opposition to a flow of current --- Ohm’s law – V = IR or I = V/R Electronic Components & Circuits – Electronic components or parts control the flow of electricity --- each component has its own symbol – Circuits --- different forms in which components are connected – Schematics --- drawings that show plans for circuits – A resistor is used to control the flow of current --- 0.1 – 106 – Color coded bands indicate the resistance in ohms – Semiconductors are neither good insulators or good conductors, e.g silicon – A diode is made using a semiconductor, it lets current flow in only one direction Electronic Components & Circuits Transistor – A resistor that lets a small amount of current control the flow of a much larger amount of current, e.g. motors, computers – It is a square wafer a few thousandths of an inch on a side – A thermistor has a resistance that changes with temperature – A photoresistor has a resistance that changes with the amount of light hitting it Printed Circuits – Solder is a method of joining two wires together – Wires’ contact causes an unintended flow of current --- short circuit --- use of insulation – A printed circuit board is a thin board of an insulating material like fiberglass – The conducting paths are photographically placed over it Electronic Components & Circuits – Once components are mounted on the board, they can be soldered by an automatic soldering machine Integrated Circuits – It provides a complete circuit on a tiny bit of semiconductor – They are often less than 1/10th of an inch in length and width – The drawing of a chip is photographically reduced to form a mask – Chips have replaced large bulky circuits and are quite less in volume and price – Computers are built using large ICs Analog and Digital Circuits – An analog circuit works with analog signals – In digital circuits, a voltage above a certain value is coded as a 1 and a voltage below that value is coded as a 0.