HOW TO SOLVE PROBLEM IN CURRENT ELECTRICITY
current is the rate of flow of electron per unit time, is
the quantity of electrons that flow through a conducting wire. current I= dQ/dt
, where Q is the quantity of the current
and t is the time in seconds.
to calculate the quantity of current flowing through a
conducting wire of length L, cross sectional area A, the electron as an charge
q, if n number of electrons passes through a thin conducting wire , then the
total current Q, that flow can be given
by
Q=qnAL
if the wire has a drift velocity dv, the time
taken for the current to move from one end to another is , t=L/ dv ,
therefore L= dv t
now the current Q=qnAL
will be Q=qnA. dv t
From above I =Q/t
I= [qnA. dv t]/t = qnA. dv
CURRENT DENSITY=
quantity of current per unit cross sectional area at any point in space.
J= Q/A= qnA. dv/A
J= qndv
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