The current in a wire is 
. Charge 
passes one point in the wire in time 
. State
the relation between , and ,
which of the quantities , and are base quantities.
The current in the wire is due to electrons, each with charge 
, that move with speed 
along the wire. There are 
of these electrons per unit volume.
For a wire having a cross-sectional area 
, the current is given by the equation:
where 
is a constant.
State the units of , , , and in terms of the base units.
By considering the homogeneity of the equation, determine the value of .
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