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SCIENCE 9
UNIT 4
ELECTRICAL PRINCIPLES AND TECHNOLOGIES
TOPIC 1 ELECTRIC CHARGES
STATIC ELECTRICITY- a charge produced by rubbing or touching objects together
UNBALANCED CHARGES- a more correct term for static electricity, because the
charges are not stationary; rather they move
LAWS OF CHARGES- Laws that describe the behaviour between charged and
uncharged objects:
1. Unlike charges attract
2. Like charges repel
3. Charged objects attract uncharged (neutral) objects
INSULATORS- any material in which the charge stays on the spot where the object is
rubbed; most non-metals are insulators
CONDUCTORS- materials that allow charges to move freely; most metals are
conductors
SUPERCONDUCTORS-materials that offer little or no resistance to the flow of charges
DISCHARGE- small spark or accumulated charge
NEUTRALIZED- became balanced
GROUNDING- connecting an object to Earth with conducting wire to safely rebalance a
charge
TOPIC 2 ELECTRICITY WITHIN A CIRCUIT
CIRCUIT- continuous pathway for a charge
BATTERY- a combination of cells, either wet or dry
SWITCH- used to open or close a circuit to control the flow of current through it
RESISTOR SYMBOL- used to represent one of many different loads in a circuit diagram
LOADS- items along a circuit that convert electricity into other forms of energy
AMPERES- the unit used to measure electric current (A). Milliamperes (mA) is also
commonly used
GALVANOMETER- an instrument used to measure very weak current
AMMETER- an instrument used to measure larger currents
POTENTIAL DIFFERENCE- the difference in potential energy per unit of charge
between one point in the circuit and another point in the circuit
VOLTAGE- a common term referring to potential difference
VOLT- standard unit for voltage (V)
VOLTMETER- the instrument used to measured voltage
TOPIC 3 RESISTING THE MOVEMENT OF CHARGE
RESISTANCE- the property of a substance that hinders motion of electric charge and
converts electric energy into other forms of energy
OHM- the standard unit for resistance
OHMMETER- an instrument to directly measure resistance
OHM’S LAWR=V
I
Resistance = voltage (potential difference)
current
Voltage (potential difference) = current x resistance
Current = voltage (potential difference)
Resistance
V = IR
I=V
R
SERIES CIRCUITS- circuits with only one current path
BRANCH- each current path in a parallel current; a parallel circuit has a series of
branches connected side by side
TOPIC 4 THE ENERGY CONNECTION
THERMOCOUPLE- a loop of two wires made of different types of metals that converts
heat to energy
THERMO-ELECTRIC GENERATOR- plants that burn fossil fuels to produce electricity
TOPIC 5 PORTABLE POWER
ELECTROCHEMICAL CELL- voltage that is generated by placing different metals in a
solution
ELECTRODES- the two metals in a voltaic or electrochemical cell
ELECTROLYTE- a substance that conducts an electric current, and in which the
electrodes are placed
PRIMARY CELL- a battery that cannot be charged
SECONDARY CELL- a rechargeable battery
TOPIC 6 GENERATORS AND MOTORS
ELECTRIC GENERATOR- a device that converts mechanical energy into electric
energy
ELECTROMAGNET- a strong temporary magnet, created by inserting a soft iron core
into a coil of wire and then passing a current through the wire
ALTERNATING CURRENT- electricity produced in a generator where the current
flowing from the generator changes direction regularly
DYNAMO- a generator that produces direct current
COMMUTATOR- a part of the dynamo generator that serves to reverse the induced
current as it changes direction, making the current flow in only one direction
ROTOR- the rotating core of an AC motor
STATOR-a stationary part of a motor surrounding the rotor, The simplest form of stator
is a two-pole electromagnet
TOPIC 7 ELECTRICITY IN THE HOME
TRANSFORMERS- used to “step-up” the voltage for efficient transmission of current
over long distances
CIRCUIT BREAKER- acts as a switch and safely device that can cut all power coming
into the home
FUSE- a device containing a metallic conductor that melts when heated by excessive
current
NEUTRAL WIRE- one of the “live” wires in electric cables, which returns low energy
electricity back to the breaker panel; the neutral wire is white and insulated
HOT WIRE- one of the “live” wires in electric cables, which carries high energy
electricity; the hot wire is black and insulated
GROUND WIRE- a device to safely channel any energy that has “leaked” out; the
ground wire is either bare copper or covered with green insulation
ELECTRICAL CODE- the set of standards for electrical work
DIGITAL ELECTRONIC TECNOLOGY- machines that process numerically coded
information
BINARY CODE- two states (on or off) that represent numbers and letters
TRANSISTORS- electronic switches in modern digital devices
POWER- energy per unit time
Power (in watts) = Energy (in joules)
Time (in seconds)
P=E
t
Power (in watts) = Current (in amps) X Voltage (in volts) P = IV
Current = Power
Voltage
I=P
V
Voltage = Power
Current
V=P
I
EFFICIENCY = USEFUL ENERGY OUTPUT
TOTAL ENERGY INPUT
SHORT CIRCUIT-
X 100%
TOPIC 8 ELECTRICITY PRODUCTION AND THE ENVIRONMENT
THERMO-ELECTRIC GENERATOR- plants that burn fossil fuels to produce electricity
NON-RENEWABLE RESOURCES- fuels that are consumed faster than they can be
replaced by nature
RENEWABLE RESOURCES- resources that can be continually replenished
OPEN PIT MINING-mining in which the fuel, such as coal, is uncovered and dug
directly from the ground
SCRUBBERS-a device that uses a sorbent to reduce oxide emissions
GREENHOUSE GAS- gases that help regulate the temperature on Earth by holding in
the heat from the Sun in our atmosphere
NUCLEAR FISSION- the process whereby uranium is split into smaller atoms, releasing
energy
THERMONUCLEAR ELECTRIC GENERATION- using the energy released in nuclear
fission to generate electricity
THERMAL POLLUTION-occurs when warm water is returned directly to the lake or
river from where it is taken, increasing the water temperature
CONGENERATOR SYSTEMS- electricity generating stations that produce electricity
and also supply thermal energy