Test: Admittance - Electrical Engineering (EE) MCQ

It is the measure of flow of current which is allowed by the circuit. 

Key Points:
Admittance (Y) is the measurement quantity that tells us how easily a conducting device can allow the flow of current through it. 

Admittance can be defined as a reciprocal of impedance (Z). i.e Y = 1/Z

Admittance measures the flow of current allowed by the circuit which is the inverse of the impedance function.

Admittance (Y):

The admittance of an AC circuit is defined as the reciprocal of its impedance (Z) i.e.

Y = 1 / Z = I / V

The unit of admittance is siemens (S).

Impedance (Z) is the opposition to alternating current flow, admittance (Y) is the inducement to alternating current flow.

Components of Admittance:

Depending upon the nature of reactance, the impedance of an AC circuit can be expressed in the complex form as :

Z = R + j X_L

or, Z = R – j X_C

Here, R is the resistive or in-phase component of Z while X_L or X_C is the reactive or quadrature component of Z.

Using Admittance Triangle,

or,

From the above triangle,

Hence, Y = G ± j (B_c - B_L)

Formula:

The admittance(Y) can be written as:

Y = G ± jB

G = Conductance

B = Susceptance

The impedance(Z) of a circuit can be written as:

Z = R ± jX

R = Resistance

X = Reactance

The relation between impedance and admittance

Z=1Y

Calculation:

Y = 3 + j4

Resistance (R) = 3 / 25 Ω

Resistance

It is an electrical parameter that is used as the measurement of opposition to the electric current.

The reciprocal of the resistance is called the 'Admittance'.

Resistance is defined as:

R = ρl / A

ρ: Resistivity of the material

l: length of the conductor

A: Area of the cross-section of the conductor.

It is measured in Ω.

Impedance:

The complex quantity of the resistance is defined as the Impedance of a circuit. 

It is the same as that of the resistance.

Admittance

It is defined as the parameter which is used to measure the flow of current easily in a circuit.

admitatance = 1 / resistance

It is measured in Ω^-1 or Siemens(S).

From Ohm's law admittance is:

Admittance = I / V

Capacitance

It is an electrical element that stores energy in the form of a static electric charge.

Energy stored in a capacitor is:

E = 1 / 2CV²

V: Voltage across the capacitor.

SI unit is Farads. (F)

Conclusion:

Option 2 is correct.

The relationship between the impedance and admittance is given by:

 Z = 1/Y

where Z = Impedance

Y = Admittance

The impedance is analogous to admittance in the following ways:

In a parallel circuit, we consider admittance instead of impedance, where admittance is the reciprocal of impedance.

We know that admittance is the reciprocal of impedance, hence the correct expression for admittance is:
Y = 1/Z.

he unit for admittance is ohm^-1 because the unit of impedance is ohm and admittance is the reciprocal of impedance.

We know that: Y = 1/Z.
Substituting the value of Z from the question, we get
Y = 1/4 = 0.25
⇒ Y= 0.25 ohm^-1.

As the impedance increases, the admittance decreases because admittance is equal to 1 / impedance.