Electricity

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• Electricity

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Electric current

• An electric current is a flow of charge.
• Two things are needed to make charge flow
• a) an energy source, such as a cell
• b) a complete circuit of conducting
  materials.

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Electric current

• Why are electric currents useful?
• electric currents can transfer large amounts of
  energy from place to place very quickly.

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Things to remember about current

• Current is a flow of charge.
• The current transfers energy.
• Current does not get used up
• ie the current leaving the cell is identical to
  the current returning to the cell.

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Ammeters

• Ammeters are instruments that measure values for
  current flow.

Ammeter circuit symbol
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Using an ammeter

• To use an ammeter remember the following
• to make sure that all the current goes through
  it, the ammeter must be wired in series.
• It doesnt matter where the ammeter goes in a
  series circuit.
• It does matter where the ammeter goes in a
  parallel circuit.

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Electric current model - series circuit
Cell
Chemical to electrical potential energy
charge
conducting materials
Electrical potential to light energy
Lamp
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Things to remember about series circuits

• Current flow is identical in all parts of a
  series circuit.
• Any break or gap in a series circuit will stop
  everything from working
• so the position of a switch doesnt matter.
• Adding things to a series circuit will reduce the
  size of the current.

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Electric current model - parallel circuit
Cell
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Things to remember about parallel circuits

• Current flow will be different in some parts of a
  parallel circuit.
• Switch positions are important in parallel
  circuits.
• Adding things in parallel increases the current
  flow in the main part of the circuit
• this is because it creates more pathways.

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Series circuit problems
L3
L2
A1
L1
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Parallel circuit problems
L2
2A
L1
L4
A1
L3