Introduction:- The current flowing in a DC circuit is basically calculated by ohm's law. The current is equal to voltage divided by resistance ie I =V/R. But in ac circuit effective resistance offered by an inductance or/and capacitance are also to be considered. The resistance to flow of ac current by an inductance is known as inductive reactance its value is given by 2πfL where f is frequency of supply and L is inductance of inductor coil. Inductive reactance is denoted by XL. Similarly the resistance offered by a capacitor is known as capacitive reactance given by 1/2πfC where f is frequency and C is capacitance of capacitor. Capacitive reactance is denoted by Xc. A circuit with two or all three components present, the effective resistance offered by circuit is known as impedance of circuit denoted by Z. Then current I =V/Z amps. Where Z is given by formula
Resistance:- When ac supply is given to a pure resistance. The current flowing trough resistance is equal to V/R amps and it is in phase with applied voltage. The vector diagram is given below.
Pure inductance:- When ac supply is given to a pure inductance the magnitude of current is given by V/XL where XL is known as inductive reactance is equal to 2πf,L. The current is 90 degree lagging to the voltage. The vector diagram is given below.
Pure capacitance:- When ac supply is applied to a pure capacitance the current flowing through capacitor is given by V/Xc where Xc is known as capacitive reactance, given by 1/2πfC. The current is leading voltage by 90 degree. The vector diagram is given below.
Series R L circuit:- Any inductance can never be a pure inductance it has some internal resistance also. So any inductance can be considered as an inductance in series with a resistance. So for this effective resistance offered is given by Z = √R2+XL2. So the current through inductance is I = V/Z amp. Current is lagging voltage by by an angle Φ = Cos-1 R/Z.
Series RC circuit:- When ac supply is applied to a series circuit of resistance and capacitance. In series combination of resistance and capacitance the resistance offered by circuit is given by impedance Z = √R2+ Xc2. So that current through circuit is I = V/Z. The current is leading voltage by an angle Φ = Cos-1 R/Z.
Series R L C circuit:- In series RLC circuit the current flowing through circuit is given by I = V/Z where Z is impedance of circuit given by formula
The current may be leading or lagging the voltage as per the value of capacitive / inductive reactance which ever is greater. The phase angle is given by Φ = Cos-1 R/Z. The difference of XL and Xc taken.
In this way the current and power factor of any series circuit can be calculated.
Resistance:- When ac supply is given to a pure resistance. The current flowing trough resistance is equal to V/R amps and it is in phase with applied voltage. The vector diagram is given below.
Series R L circuit:- Any inductance can never be a pure inductance it has some internal resistance also. So any inductance can be considered as an inductance in series with a resistance. So for this effective resistance offered is given by Z = √R2+XL2. So the current through inductance is I = V/Z amp. Current is lagging voltage by by an angle Φ = Cos-1 R/Z.
Series RC circuit:- When ac supply is applied to a series circuit of resistance and capacitance. In series combination of resistance and capacitance the resistance offered by circuit is given by impedance Z = √R2+ Xc2. So that current through circuit is I = V/Z. The current is leading voltage by an angle Φ = Cos-1 R/Z.
Series R L C circuit:- In series RLC circuit the current flowing through circuit is given by I = V/Z where Z is impedance of circuit given by formula
The current may be leading or lagging the voltage as per the value of capacitive / inductive reactance which ever is greater. The phase angle is given by Φ = Cos-1 R/Z. The difference of XL and Xc taken.
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