Page 312 - General Knowledge

GENERAL KNOWLEDGE 2019

9. ELECTRICITY

 Electricity is a basic part of our nature and it is one of our most widely used forms of energy.
 Conductors are materials through which electricity can flow. Copper, silver and aluminium
are good conductors.
 Insulators are materials through which electricity cannot flow. Glass and plastic are good
insulators.
 An electric circuit is a complete conducting pathway for the electric current to flow from one
terminal of an electric cell or battery back to the other terminal.
 It consists of three essential items:
 A power supply to provide the electrical supply
 A load in which electrical energy is converted into other forms of energy
 A conducting path which allows electrons to flow around the circuit.
Current
 An electric current is a flow of electric charge. It is measured in amps (A), using an ammeter.

 For current to flow, there must be a complete pathway from the negative terminal to the
positive terminal. Charge has the symbol Q, and is measured in coulombs, symbol C. The
current flows from the positive side to the negative side around the circuit. The flow depends
on three factors:
 The pressure causing the current to flow
 How fast the current flows
 What resistance to its flow the current meets in the conductor
Voltage

 The amount of energy forcing electric charge through the circuit.
 It is measured in volts (V), using a voltmeter.
 The bigger the voltage, the faster the current flow.
Resistance
 The measure of how much a conductor slows down the flow of current. It is measured in
ohms, and it there are factors that determine the resistance.
 These include the type of material, its length and the thickness of it.
 Resistors are components which are used to provide resistance to current flow.
Ammeter
 It is used to measure the size of an electric current flowing in a circuit.
 It measures the current in amperes (A) or as mill amperes (mA).
 The +ve terminal should always be connected in series so it is closer to the power supply. It
is placed in series with the circuit.
Voltmeter
 It is used to measure the voltage gain across the terminals of a power supply or voltage drop
across parts of an electric circuit. (V) It should be connected in parallel to a globe.

Superconductors
 Superconductors are conductors of electricity where the resistance is non-existent or very
little.
 The resistance to the electricity in a wire will occur as the temperature is cooled towards
absolute zero (-273.14 degrees C).

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