Which is true for admittance?

Question

Examoogle · Accepted Answer

$Y = \frac{I}{V}$

Explanation: Admittance ($Y$) is defined as the reciprocal of impedance ($Z$) in an electrical circuit. It represents the ease with which an alternating current flows through a circuit element or network, measured in Siemens (S).

Working Principle: In an A.C. circuit, Ohm's law is expressed as $V = I 	imes Z$. By rearranging this for admittance, we define $Y = \frac{1}{Z}$. Substituting $Z = \frac{V}{I}$ into the definition of $Y$ gives $Y = \frac{1}{\frac{V}{I}} = \frac{I}{V}$, which indicates how much current flows for a given applied voltage.

Key Formulas: $Y = \frac{1}{Z} = \frac{I}{V}$ — Fundamental definition of admittance; $Y = G + jB$ — Complex form involving Conductance (G) and Susceptance (B)

Key Points: The SI unit of admittance is the Siemens (S) or Mho ($mho$).; Admittance is a complex quantity composed of real part conductance and imaginary part susceptance.; Higher admittance indicates a lower impedance and therefore higher current flow for a given voltage.

Advantages: Simplifies calculations in parallel A.C. circuits as admittance values add directly ($Y_{total} = Y_1 + Y_2 + ... + Y_n$).; Useful for analyzing networks containing parallel branches.

Disadvantages: Less intuitive than resistance or impedance for series circuits.; Involves complex numbers, which can lead to calculation errors if polar and rectangular conversions are not managed carefully.

Applications: Power system analysis for parallel load distribution.; Radio frequency (RF) circuit design and filter synthesis.

Additional Info: Option C ($Y = V/I$) represents impedance ($Z$), which is the inverse of admittance.. Option D ($Y = Z$) is mathematically incorrect as $Y = 1/Z$.

Answer: B is correct — Admittance ($Y$) is the ratio of current ($I$) to voltage ($V$), which is the reciprocal of impedance ($Z = V/I$).

Exam Tip: Always remember that in parallel circuits, it is easier to sum admittances than to calculate total equivalent impedance using the reciprocal sum formula.

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