CIE IGCSE Physics

Revision Notes

4.2.5 Current

Electric Current

  • When two oppositely charged conductors are connected together (by a length of wire), charge will flow between the two conductors

 

Flow of charge, IGCSE & GCSE Physics revision notes

Charge can flow between two conductors 

  • This flow of charge is called an electric current
    • The greater the flow of charge, the greater the electric current

 

Extended Only

Charge, Current & Time

  • The current is the charge passing a point in a circuit every second

(It is helpful to think of current as the charge per second)

  • Charge, current and time are related by the following equation:

Current charge equation, IGCSE & GCSE Physics revision notes

  • Where the symbols:
    • Q stands for charge (measured in coulombs, C)
    • I stands for current (measured in amps, A)
  • You can rearrange this equation with the help of the formula triangle:

Current charge time triangle, IGCSE & GCSE Physics revision notes

Use the formula triangle to help you rearrange the equation

 

Measuring Current

  • Current is measured using an ammeter
  • Ammeters should always be connected in series with the part of the circuit you wish to measure the current through

Measuring current, IGCSE & GCSE Physics revision notes

An ammeter can be used to measure the current around a circuit

 

Current & Electrons

  • In a metal, current is caused by a flow of electrons

electrons-and-current, IGCSE & GCSE Physics revision notes

In metals, the current is caused by a flow of free (delocalised) electrons

 

Extended Only

Electrons & Conventional Current

  • Electrons are negatively charged
  • This means that the electrons flow from negative to positive
  • Conventional current, however, is still defined as going from positive to negative

Electrons vs current, IGCSE & GCSE Physics revision notes

By definition, conventional current always goes from positive to negative (even though electrons go the other way)

 

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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