Topic 6: Generators and Motors A device that converts mechanical energy into electrical energy is known as a GENERATOR. What materials are needed to assemble an electromagnet (there are three things)? A power source, a coil of wire, and a soft iron core. AC stands for ALTERNATING CURRENT (two words). DC stands for DIRECT CURRENT (two words). An AC GENERATOR has a coil of wire rotating inside a stationary field magnet. Massive AC GENERATORS can be used to power entire cities. A DC GENERATOR is also called a dynamo. It sends current in only one direction because of how the armature is connected to a split ring commutator. An electric motor is constructed in the same way was a generator, but instead it takes ELECTRIC ENERGY (two words) and converts it to MECHANICAL ENERGY (two words). Topic 7: Electricity in the Home Define TRANSFORMER (but remember that there are two types): Can increase or decrease voltage for efficient transmission over long distances. “Step up” transformers increase voltage, “step down” decreases voltage. Define CIRCUIT BREAKER: A switch and safety device that can cut off all power coming into the home. Electrical cables contain three wires. Name them, describe what they do, and what colour each one is. Black (hot), white (neutral), copper/green (ground). Only the black and white wires carry electrical current. Define POWER: Energy per unit of time. In electricity, it’s the amount of electric energy (measured in joules) that is converted into other forms of energy every second. Label the two triangles using power, energy, and time in one, and power, current, and voltage in the other. Also include the units of each. P
E
I
P
V
T
1000 W is equal to 1 kW. Most power companies measure electric energy in kWh (kilowatt hours). Define EFFICIENCY: A ratio comparing the amount of energy output with the energy that went into a device. What is the equation for calculating efficiency? Efficiency = output energy x 100% input energy Make sure you know how to complete some of the problems that we worked on in class! Answer KEYS are on my website!! Topic 8: Electricity Production and the Environment Define THERMO-­‐ELECTRIC GENERATOR: Convert heat energy into electric energy Define NON-­‐RENEWABLE: Resources that are limited. Cannot be replaced as fast as they are being used. Define RENEWABLE: Resources that can be continually replenished. Define GEOTHERMAL ENERGY: Energy that comes from the heat of the Earth Define BIOMASS: Solid material from living things that can be burned in thermo-­‐electric generators. Define THERMAL POLLUTION: A change in the environment that is caused by heat. This happens when warm water is returned directly to the lake or river from which it was taken. It was used in the electric energy generating process. Define THERMONUCLEAR: When nuclear fission occurs it creates energy in the form of heat. This heat is then used to increase the temperature of water, turning it into steam, which is then used in the generator. Define COGENERATION SYSTEMS:
Cogeneration, combined heat and power, is the simultaneous production of electrical and thermal energy from one fuel source. The waste heat from electricity generation is recovered and used for applications such as space heating and cooling, water heating, and industrial process heat. By making use of the waste from one process in the production of the other, substantial gains in energy efficiency can be realized.