Chapter 8: Electricity and magnetism Unit 3: Energy in Motion Chapter 8: Electricity and magnetism

Electricity and Magnetism Electricity and Magnetism – the two forces are inseparable. {Complicated electrical equipment and electronics work because of the positive and negative charges that are a part of tiny atoms}

Electricity Man observed electricity long before the parts of an atom were understood. The ancient Greeks noticed that amber produced a spark when rubbed with fur. Only within the last 150 years has man been able to harness electricity for practical use. Thomas Edison invented the electric light bulb in 1879, revolutionizing the use of electricity.

Electricity Static Electricity – occurs when electrical charges build up on the surface of an object (rubbing 2 objects together may cause electrons to move from one object to the other) One object gains extra electrons and has a negative (-) charge and the other object loses electrons and has a positive (+) charge Objects with like charges (positive & positive or negative & negative) repel each other

Electricity Objects with unlike charges (positive & negative) attract each other When you walk across carpet on a cold day, your shoes collect charges. These charges build up on your body and when you reach for the doorknob, the electricity discharges, or jumps, from your hand to the doorknob. This causes a spark and a shock. The most dramatic kind of static electricity is lightning – it is a result of charges building up in the clouds during a thunderstorm.

Current Electricity In order for electrical energy to be useful, it must have a continuous flow of electrons. Current electricity is the flow of electrons around a circuit. Two things are necessary to make current electricity There must be a circuit, a continuous unbroken path, through which electricity can flow The circuit must have a power source that causes the electrons to start moving

Conductors and Switches Conductor – a material that allows electricity to flow through it easily. Most metals are good conductors because metals loosely hold their electrons. Switch – a conductor that can be moved to either bridge or not bridge the gap in a circuit.

Conductors and Switches Closed circuit – when the switch is closed, the circuit is complete, so electricity flows easily Open circuit – an open switch breaks the circuit, so the electrons cannot travel through a complete path Short circuit – electricity may take an unexpected path because it always flows through the easiest path. Short circuits can cause sparks and fires. Fuses and circuit breakers provide buildings and houses protection from short circuits

Insulators and Resistors Insulator – a material that does not conduct electricity well (it doesn’t allow electricity to flow through it). Plastic, wood and glass are all good insulators. A wire without a coating of plastic would be very dangerous. Resistor – a material that reduces the flow of electrons. As electrons push harder to get through a resistor, friction causes the resistor to become hot. The resistor heats up and it may begin to glow. The heating element in a toaster and the metal wire, or filament, in a light bulb are resistors.

Kinds of Circuits Series circuits – has only one path, or one circuit, for the electricity to travel. If the path has a break at any point, the current cannot complete the circuit (when a filament in a light bulb burns out, the circuit opens and breaks the path of electricity). Parallel circuits – has multiple paths for the electricity to flow (On a newer Christmas light strand, if one bulb burns out, it does not affect the other circuits. The other bulbs will light because the electricity can complete its path.)

Measuring Electricity Volt – the measurement of the amount of electricity push or force in a circuit (the wiring in a typical house carries 115-120 volts of electrical force) Watt – the measurement of power, or how fast work is done (i.e.; a 100-watt light bulb uses more power than a 60-watt light bulb) The electric meter on a house measures the amount of power being used in the house. Power is measured in kilowatts (1kW = 1000 watts).

Measuring Electricity Ampere (amps) – the unit used to measure how much current flows through a given part of a circuit in one second (circuit breakers typically allow 15 0r 20 amperes of current to pass through a circuit safely – if more amperes than allowed pass through the circuit, the circuit will open) The 3 basic units of measurement – volts, watts, and amperes – are related to each other (watts divided by volts = amps, so 240 watts divided by 120 volts = 2 amps)

Batteries Electric cell – a device consisting of two metals and an electrolyte (any liquid or paste that conducts electricity) that cause a chemical reaction. It uses chemical energy to produce an electrical current. Battery – device that uses chemical reactions to provide the force needed for an electrical current. A battery has one or more electric cells.

Batteries Wet cell batteries are rechargeable batteries that must remain upright and are not very portable. The electrolyte fluid used in a wet cell battery is usually corrosive or poisonous. Dry cell batteries are more commonly used. Instead of having electrolyte fluid, they have an electrolyte paste. They can be used in any position and they are sealed and less likely to expose a person to the poisonous electrolyte. In “dead” batteries, one of the metals is used up or the electrolyte is depleted.

Magnetism Magnet – any material that has the ability to attract iron (they also attract objects made from nickel and cobalt, and they have 2 poles – a north pole and a south pole) Magnetic field – the area around a magnet that magnetism affects. Magnetic force is strongest at the poles of a magnet and the middle is the weakest. Magnets are similar to static electricity in that they both can repel and attract other objects (the south pole of one magnet is attracted to the north pole of another magnet; two south poles or two north poles will repel each other)

Electricity and Magnetism Electricity and magnetism are related – a flow of electricity can produce a magnet, and a magnet can produce electricity Hans Christian Oersted (UHR sted) discovered that current traveling through a wire produces a weak magnetic field in the wire in 1820. In 1831, Joseph Henry and Michael Faraday both discovered (although not working together) that moving a magnet around or through a loop of wire produces electricity in the wire. They also found that moving a wire between the north and south poles of 2 magnets produces electricity in the wire. Either the wire or the magnet must be moving. (Generators use this principle to make electricity)

Electromagnets In 1825 William Sturgeon discovered that adding a metal core to a coil of wire increases the magnetism even more. Electromagnet – a coil of wire with a core attached to an electrical source. When electricity travels through the coil of wire, the core acts like a magnet. If no electricity runs through the coil, the core is not magnetized.

Generators Generator – a machine that converts motion into electrical energy Most electric power plants use turbines to power generators. The turbine has blades that are moved by water, steam, or wind. As the blades turn, a shaft turns a magnet within a coil of wire. The spinning magnet creates an electric current in the coil of wire. Most electrical power plants have stationary coils and moving magnets rather than spinning coils and stationary magnets, because this takes less energy.

Electronics Electronic device – an object that uses electricity to communicate information Electronic devices are similar to electrical devices, but they are not the same. They both use current electricity, and both can do work. However, electronic devices can communicate information, but electrical devices cannot. Electrical device = toaster Electronic device = television

Electronics Electrical signal – an electric current that carries information Electronic devices use a code called the binary system. The binary number system is used to communicate in computers. The numeral 0 indicates an open circuit The numeral 1 indicates a closed circuit Using this code, electronic devices can communicate almost any piece of information

Integrated Circuits Integrated circuit – (IC) a very small circuit with all of its parts built into it. Integrated circuits are called microchips because they are made from chips of silicon. Silicon, a major ingredient of sand, is an excellent semiconductor. Semiconductor – a material that conducts electricity better than insulators but not as well as conductors Integrated circuits signal information by varying the amount of electricity by opening and closing circuits in sequence.

Computer Parts The electronic device called a computer uses many, many integrated circuits connected together. A computer can communicate information and save, process, and recover that information. CPU (central processing unit) acts like the brain of the computer. It tells the other parts what to do. ROM (read only memory) is built-in memory and programs, sets of instructions that tell the computer what to do. It is like your long-term memory! RAM (random access memory) stores facts temporarily. It is similar to your short-term memory.

Computer Parts A computer cannot save information in RAM or ROM. It can be saved in data storage devices, like a hard drive, CD or flash drive. Computers gain information through input devices such as keyboard, mouse, modem or scanner. It gives information through output devices such as monitors and printers.

Computer “Intelligence” A computer knows only two things, open and closed circuits. An open circuit means 0 or no. A closed circuit means 1 or yes. By sequencing the open and closed circuits, a computer can signal information using the binary number system. A computer only seems to have intelligence – it can only do what the programmer and designer tell it to do. It can recall facts quickly, but it doesn’t understand the facts.

Computer “Intelligence” The Bible says that true intelligence is more than just knowing facts. Wisdom is knowing, understanding, and remembering the facts. Understanding is knowing when and how to use the facts. Discerning what is true and what is a lie is also a part of understanding. The greatest of all wisdom is to know and understand God (Jeremiah 9:23-24) “Get wisdom; get understanding: forget it not.” (Proverbs 4:5)