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Electricity (Relationship between Electric Current & Potential…
Electricity
Electric Charge & Current
Electric field
A region around a charged particle or object within which a force would be exerted on other charged particles or objects
Electric current
I = Q/t
Q = ne (n= number of electron) (e=the charge of one electron)
Rate of electic charge flow through a cross section of a conductor
Scalar quantity
Electric charge
Different charge-attract
Source of electrical force
Electrial force between two charges-Electrostastic force
Same charge-repel
One electron carry charge of 1.6 X 10^-19 C (coulombs)
Electromotive Force & Internal Resistance
Electromotive Force
The work done by a source in driving a unit charge around a complete circuit.
Unit: Volt, V
Letter ‘ε’ represent e.m.f
e.m.f is not a kind of force
Formula
ε=V+Ir
ε=I(R+r)
Internal Resistance
Resistance present inside a cell, which is against the moving charge due to electrolyte in the cell
The presence of internal resistance causes a voltage drop when a current flows
Series and Parallel circuits
Series circuit
Has more than one resistor, but only one path through which the electricity flows
I=I1=I2=I3
V=V1+V2+V3
R=R1+R2+R3
Parallel circuit
Electric current passes through two or more branches or connected parts at the same time before it combines again
I=I1+I2+I3
V=V1=V2=V3
1/R=1/R1+1/R2+1/R3
Relationship between Electric Current & Potential Difference
Gravitational Potential
Work done per unit mass to move a point from infinity to another point
V=-GM/r
Electric Potential
Work done by moving a charge particle from infinity to another point is equal to the electric potential
Potential Difference
Difference in the amount of energy that charge carriers have between two points in a circuit
Electric Potential-Work required to move charge in electric field
Work done that required to move one coulumn of charge between two points
V=W/Q
1V=1JC^-1
Ohm's Law
Potential difference across an ohmic conductor is directly proportional to the electric current
V ∝ I
V=IR
Resistance
ratio of potential difference to the electric current.
Unit is ohm,Ω
Factors effect resistance
The longer the length of a conductor, the bigger is the resistance
The bigger the cross-sectional area of a conductor, the smaller is the resistance
Type of materials
Resistance of a metallic conductor increases with increasing temperature
Electrical Power & Energy
Electrical Energy
E= VQ
E= VIt
Energy derived from electric potential energy or kinetic energy
Electrical Power
Rate, per unit time, at which electrical energy is transferred by an electric circuit
E=Pt
P=VI
P=I^2R
P=V^2/R
Efficiency
(Output energy / Input energy) X 100%
(Output power / Input power) X 100%
