Definition electric current in a wire

Electric current : the amount of charge per unit time that crosses the imaginary surface of a wire.

I  = Δ Q /Δt

  • I       electric current  in A
  • ΔQ  the charge passed in C  (1 Coulomb is the unit of charge)
  • Δt    time in s (!) 

Example

The electric current in a wire is 500 mA.

Calculate the charge passed through the imaginary surface of the wire in 2.0 min

I  = Δ Q /Δt

0.5 = Δ Q/120

Δ Q = (0.5)( 120) = 60 C

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