### 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.