BY APPLYING THIS LAW THEREFORE WE SHOULD UNDERSTAND THE RELATIONSHIP THE CORE ELEMENTS OF THE CIRCUITS WHICH IS :
VOLTAGE CURRENT AND RESISTANCE
REPRESENTED IN MATHEMATICAL FORMULA
V = I times Z
VOLTAGE IN VOLTS (V)CURRENT IN AMPERES (I)IMPEDANCE IN OHMS (Z)
The term impedance is used to include both inductive and capacitive reactance and resistance because all three are forms of opposition to the flow of current.
In AC circuits impedance is made up of electrical resistance, electrical reactance and both of them impede the flow of currents through a circuits .
Most of everyday use ,specially home appliances and other device are both reactive and resistive loads. so it is important to know all this things to measure electrical consumption.
What is resistive loads ?>
A common example of resistive loads are light bulb and heater .
In an AC resistive circuit, the current alternates exactly in step with the voltage. In either case, Ohms Law can be applied and we can measure resistance directly on a circuit like DC circuits do.
so ..applying ohms law formula
Ohm's Law V = A x R where:
V = voltage (volts)
A = current (amps)
R = resistance (ohms)
A = current (amps)
R = resistance (ohms)
But still we treat resistance as impedance in AC circuits.
Reactive loads
Reactive loads are loads that treat both reactance and resistance which behave differently in a circuit.
It may contain either capacitor or inductor which we cant measure directly .Reactive loads create impeding force to change the flow of current, which we can measure as capacitive or inductive reactance
Whenever there is an inductor, or coil, in a circuit, we call its impeding force to current flow "inductive reactance." For a circuit with a capacitor, the impeding force is called "capacitive reactance."
Inductive reactance XL
To understand more, Inductor is simply a coil of wire. But when current is present in a coil it generate electrical field or" induced field "which depends on the number of turn .The greater the number of turns the higher the induce field.This phenomenon is called "inductance."
To measure the inductive we have
XL =2p x f x L.
Where:
XL = inductive reactance measured in ohms
2 = a constant (2 x 3.1416 = 6.28)
f = the AC frequency of the electrical supply in hertz
L = the inductance value of the coil in henries.
2 = a constant (2 x 3.1416 = 6.28)
f = the AC frequency of the electrical supply in hertz
L = the inductance value of the coil in henries.
Capacitive Reactance XC
When a capcitor i s present on a AC circuits we can call it a capacitive circuits which behave differently .
Unlike inductors, a capacitor store ,charge or build voltage potential when electrical current is present.
The amount of charging a capacitor can achieve is called capacitance and is measured in Farads, or microfarads ,µF
.
A capacitor is comprised of two or more electrically conductive surfaces called "plates," insulated from each other by a material called a dielectric. Materials such as air, paper, mica and oil can be used as dielectrics.
Capacitor oppose the alternating current flow due to capacitive reactance which can be measured in Ohms
The formula for calculating the Capacitive Reactance, or impedance of a capacitor is:
Capacitive reactance, denoted as x sub c (XC), is equal to the constant one million (or 106) divided by the product of 2p ( or 6.28) times frequency times the capacitance .
where:
XC = Capacitive reactance measured in ohms.
f = is the AC frequency in Hertz.
C = is the capacitance in microfarads.
f = is the AC frequency in Hertz.
C = is the capacitance in microfarads.
In applying the Ohms law in a capacitive circuit ? first we must determine the capacitive reactance value
for example :
If we have 40 micro farad capacitor connected 230 v 60 Hertz AC source
1,000,000
XC = --------------------------------------------
6.28 x 60Hz x 40 micro farad
= 66.3 Ohms
Applying the ohms law
I = V/Xc
I = 230 V /66.3 ohms
I = 3.4 Amps
