Download Meeting NCTE – 7th Feb 2008

Electric Circuit
Components are connected together with electrical wire to form
a closed loop.
Components are
represented by symbols
Electric Circuit
•Electrical wire used to connect components is a conductor.
•A conductor allows electric current to flow through it easily.
•Good conductors include: copper, gold, silver, tin
•Copper wire is generally used as it is most cost effective.
•All electrical wires have a plastic cover.
•Plastic is an insulator.
•An insulator does not allow current to flow through it.
•Avoids electric shock.
•Insulators include: plastic, glass, wood
Electric Circuit
Electric Current is the flow of electrons around a circuit.
Electrons have a negative charge
Electric Circuit
•Electric current is measured with an Ammeter
•The ammeter is placed into the circuit (in series)
•Unit of measurement is the Ampere or ‘amp’
•Represented by the letter I .
I=3A
Electric Circuit
•Voltage is measured using a Voltmeter.
•The voltmeter is placed across a component (in parallel)
•Unit of measurement is the Volt.
•Represented by letter V.
Electric Circuit
•Resistance is the opposition to the flow of electric current.
•All components have resistance.
•Electrical wire has resistance.
•Unit of measurement is the Ohm (Ω)
•Represented by the letter R
Ohm’s Law
Voltage , Current & Resistance are calculated using Ohm’s Law
V  IxR
V
I
R
V
I
R
V
R
I
Series Circuit
•Components are connected one after the other
•There is only one path for current to flow around
•The current at all points in a series circuit is equal
Series Circuit
The voltage is shared between the components in a series circuit.
•Components of equal resistance : voltage is shared equally
Series Circuit
The voltage is shared between the components in a series circuit.
•Components of unequal resistance : voltage is shared
proportionally
Parallel Circuit
•Components are connected side by side
•There is more than one path for current to flow around
Parallel Circuit
The voltage across each path is always the same as the applied voltage
• When component resistance in each path is the same
Parallel Circuit
The voltage across each path is always the same as the applied voltage
• When component resistance in each path is different
Parallel Circuit
The voltage across each path is always the same as the applied voltage
• When there is more than one component in a path
Parallel Circuit
•The current is divided between the paths proportionally (Ohm’s Law)