a) electric charge

• define electric current

• state the formula for electric current

• electric current = the rate of the flow of charge (the coulombs of charge that pass a specific point in a circuit per second)

• I = ∆Q/∆t

  • electric current (A) = the charge transferred (C) / time (s)

• explain the concept of elementary charge

• explain what is meant by a relative charge

• one coulomb contains many electrons/protons

  • the (constant) elementary charge (e) of each electron/proton in one coulomb is ±1.6×10^-19C

  • the charge of any charged object is a multiple of the elementary charge, so charge is quantised

• relative charge is measured against the elementary charge

  • ±1e = ±1.6×10^-19C

  • the relative charge of a an electron/proton = ±1e

• explain how objects become electrically charged

• state the formula for the net electric charge of an object

• most charged objects have either lost (gained a positive charge) or gained (gained a negative charge) electrons

• Q = ±ne

  • net charge of an object (C) = number of electrons lost or gained × elementary charge

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