Question

The reciprocal of impedance of an electric current is?
(A) Admittance
(B) Susceptance
(C) Conductance
(D) Reactance

Answer 1

Hint The reciprocal of impedance is admittance. The mathematical expression for admittance is: $Y = \dfrac{1}{Z}$ where, Z is the impedance. Unit of impedance is ohm, $\Omega$ and the unit of admittance is mho,$\mho$.

Complete step by step solution
In quantitative terms, in a two terminal electronic circuit, the ratio of the complex representation of a sinusoidal voltage,$V = |V|{e^{i(\omega t + {\phi _V})}}$ between the two terminals of the circuit and the complex representation of current, $I = |I|{e^{i(\omega t + {\phi _I})}}$flowing through the two terminals is termed as impedance, Z. In polar form, it is represented as $Z = \left| Z \right|{e^{i\theta }}{\text{ or as }}\left| Z \right|\angle \theta$ where, $\left| Z \right|$represents magnitude of impedance, Z and $\theta$represents argument of the complex number, Z. In Cartesian form, impedance is represented as $Z = R + iX$ where R is the resistance in the circuit and X is the reactance in the circuit.

Impedance has the same units as resistance, SI unit is ohm ($\Omega$). But, resistance is simply the ratio of voltage and current in an electric circuit, i.e. $R = \dfrac{V}{I}$ whereas, impedance is a complex ratio.
Admittance for an electric circuit is defined as the reciprocal of the impedance, i.e.$Y = \dfrac{1}{Z}$. The unit for admittance is Siemens or mho ($\mho$).

Therefore, option (A) is correct.

Note Qualitatively, impedance is the measure of the opposition to the flow of electric current in a circuit whereas admittance is the measure of how easily a circuit allows electric current to flow through it. So, there is an inverse dependence.