Cineálú Iompairchumhachta: Cén mian leis?

Cén é an Impíd Eileacra?

I réamhainn eolaíochta eileacra, is tomhas é an impíd eileacra ar an gcosaint a chuirtear i bhfeidhm ag comhdraideal nuair a chuirtear comhdraideal isteach agus a chuirtear voltaic isteach. Forbraíonn an impíd an coicéad go dtí comhdraideal neamhchothrom (AC) circuits. Tá méid agus phase ag an impíd, cosúil leis an gcóicead, atá leis an mhéid amháin.

Compared to electrical resistance, the opposition of electrical impedance to current depends on the frequency of the circuit. Resistance can be thought of as impedance with a phase angle of zero.

Is circuit inductach puroilíontach é áit a lagann an comhdraideal 90° (eileacra) i dtaobh an voltaic a chuirtear isteach. Is circuit capacitach puroilíontach é áit a dhéanann an comhdraideal 90° (eileacra) i dtaobh an voltaic a chuirtear isteach. Is circuit resistive puroilíontach é áit nach lagann ná déanann an comhdraideal leadradh i dtaobh an voltaic a chuirtear isteach. Nuair a dhreapar circuit le direct current (DC), níl aon idirbhá intíre idir impíd agus cóicead.

In a practical circuit where both inductive reactance and capacitive reactance present along with resistance or either of capacitive or inductive reactance presents along with resistance, there will be leading or lagging effect on the current of the circuit depending on the value of reactance and resistance of the circuit.

In the AC circuit, the cumulative effect of reactance and resistance is termed as impedance. The impedance is normally denoted by English letter Z. The value of impedance is represented as

Where R is the value of circuit resistance and X is the value of circuit reactance.
The angle between applied voltage and current is

The inductive reactance is taken as positive and capacitive reactance is taken as negative.

Impedance can be represented in complex form. This is

The real part of a complex impedance is resistance and the imaginary part is reactance of the circuit.

Let us apply a sinusoidal voltage Vsinωt across a pure inductor of inductance L Henry.

The expression of current through the inductor is

From the expression of the waveform of the current through the inductor it is clear that the current lags the applied voltage by 90° (electrical).

Now let us apply same sinusoidal voltage Vsinωt across a pure capacitor of capacitance C farad.

The expression of current through the capacitor is

From the expression of the waveform of the current through the capacitor it is clear that the current leads the applied voltage by 90°(electrical).

Now we will connect the same voltage source across a pure resistance of value R ohm.

Here the expression of current through the resistance would be

From that expression, it can be concluded that the current has the same phase with the applied voltage.

Impíd de Circuit RL Sraithe

Let us derive the expression of the impedance of a series RL circuit. Here resistance of value R and inductance of value L are connected in series. The value of reactance of the inductor is ωL. Hence the expression of impedance in complex form is

The numerical value or mod value of the reactance is

Impíd de Circuit RC Sraithe

Let us connect one resistance of value R ohm in series with a capacitor of cap