Current
Current is the flow of electrical charge carriers like electrons.
Current flows from negative to positive points.
The SI unit for measuring electric current is the ampere (A).
One ampere of current is defined as one coulomb of electrical charge moving past a unique point in a second. Electric current is widely used in household and industrial appliances
I = Q/t
Voltage
Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light.
Resistivity
Resistivity is directly proportional to length of conductor.
Resistivity is inversely proportional to cross sectional area of conductor.
R ∝ L
R ∝ 1/A
ஃ R ∝ L/A
ஃ R = ⍴ L/A
⍴ = resistivity of conductive material
⍴ = R A / L
Unit = Ω . m
Alloys have more conductivity and less resistivity.
Insulators have high resistivity and less conductivity
Resistors behavior in series and parallel
Series
If we have 3 resistivity materials and connected in series then total voltage drop is equal to sum of individual.
V = V1 + V2 + V3
As per ohm's law ( V= IR )
IR = IR1 + IR2 + IR3
so, R = R1 + R2 + R3
Parallel
I = I1 + I2 + I3
As per ohm's law ( V= IR )
V/R = V/R1 + V/R2 + V/R3
1/R = 1/R1 + 1/R2 + 1/R3
Power
Power is defined as work done per unit time
P = Electrical energy consumed / Time
= W/t
Unit =kWh, Joule
Frequency
Frequency is the number of times a sine wave repeats, or completes, a positive-to-negative cycle.
Our house hold power has rating 50 A current, 230 V Voltage, 50 Hz Frequency. 50 Hz means 50 AC Wave cycle in 1 second.