# IITJEE PHYSICS:Current Electricity Part -I

Agenda: Summary of Current Electricity

-A current flows along a metal or wire when battery is connected to it.
-Current in a wire is due to free electrons moving along the wire
-The Battery has a Potential difference between its poles due to chemical changes inside the battery.The Potential difference pushes the electrons alongs the metal.The Potential diffrence between the terminal is call the EMF of the battery.
-One pole of the battery is called positive pole and another one is call the negative pole.
-Current direction is opposite to the electron flow direction.
-EMF is measured in Volt

Electric current is defined as the rate at which charge flows inside the conductor
so
I=Q/t
- Its unit is Amphere
Also I=dQ/dt

Drift speed of electrons inside the conductor
vd=I/neA
Where I is the current,n is the number of the electron per unit volume ,e is the electronic charge and A is the area of the crossection of the conductor

Ohms Law

V=IR
where V is the Potential difference accross its ends
I is the current flow
And R is the electrical Resistance of the conductor.Electrical Resistance unit is Ohm

ELectrical Resistivity

It is defined as
ρ=RA/L

Where R is the Resistance
A is the crossectional Area
L is the length

Series Resistors

R=R1+R2+R3

Parallel Resistors

(1/R)=(1/R1)+(1/R2)+(1/R2)

Terminal Voltage of the Cell

V=E-Ir

where E is the EMF of the cell and r is the internal resistance of the Cell

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