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ElectricalBasic Electrical
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Equation of current in vector method is

A

I=VRI = \frac{V}{R}I=RVтАЛ

B

I=XYI = \frac{X}{Y}I=YXтАЛ

C

I2=X2+Y2I^2 = X^2 + Y^2I2=X2+Y2

D

I=XтИТYI = X - YI=XтИТY

Correct Answer

тЪЩя╕П TE тАв Technical Concept & PrincipleElectricalBasic Electrical
Option C

I2=X2+Y2I^2 = X^2 + Y^2I2=X2+Y2

Quick Summary:

In an A.C. parallel circuit, the total current is the phasor sum of the branch currents. According to the vector addition rule for orthogonal components (like active and reactive currents), the magnitude of the resultant current is found using the Pythagorean theorem, represented as I2=Ia2+Ir2I^2 = I_a^2 + I_r^2I2=Ia2тАЛ+Ir2тАЛ.

тЪЩя╕ПTETechnical SolutionConcept & Principle
ЁЯТб Explanation

In an A.C. parallel circuit, the total current is the phasor sum of the branch currents. According to the vector addition rule for orthogonal components (like active and reactive currents), the magnitude of the resultant current is found using the Pythagorean theorem, represented as I2=Ia2+Ir2I^2 = I_a^2 + I_r^2I2=Ia2тАЛ+Ir2тАЛ.

ЁЯФв Key Formulas

I=Ia2+Ir2I = \sqrt{I_a^2 + I_r^2}I=Ia2тАЛ+Ir2тАЛтАЛ тАФ Magnitude of total current

I2=X2+Y2I^2 = X^2 + Y^2I2=X2+Y2 тАФ Pythagorean relationship for orthogonal currents

тЪЩя╕П Working Principle

In A.C. circuits containing resistance (R) and reactance (X), the current components are in quadrature (90┬░ apart). The total current III acts as the hypotenuse of a right-angled triangle where the horizontal base is the active (in-phase) current and the vertical height is the reactive (quadrature) current. Consequently, the square of the resultant current equals the sum of the squares of its orthogonal components.

ЁЯУМ Key Points
  • тЦ╕

    A.C. currents cannot be added algebraically unless they are in phase.

  • тЦ╕

    The vector method accounts for the phase difference between resistive and reactive branches.

  • тЦ╕

    This concept is fundamental for calculating the power factor and total impedance in complex networks.

тЬЕ Advantages
  • тЦ╕

    Provides an accurate resultant magnitude for out-of-phase components.

  • тЦ╕

    Simplifies complex circuit analysis using right-triangle trigonometry.

тЭМ Disadvantages / Limitations
  • тЦ╕

    Only applicable for orthogonal (90┬░) components.

  • тЦ╕

    Requires knowledge of phase angles for non-orthogonal current additions.

ЁЯЫая╕П Applications / Uses
  • тЦ╕

    Power system analysis for inductive/capacitive loads.

  • тЦ╕

    Calculation of total line current in parallel R-L and R-C circuits.

ЁЯУД Additional Information
  • тЦ╕

    In the context of the question, X and Y represent the orthogonal components of the total current I, typically the active current (Icos╧Ж) and reactive current (Isin╧Ж).

  • тЦ╕

    Options A, B, and D are incorrect as they do not represent the magnitude of a resultant vector involving quadrature components.

ЁЯУК Diagram / Illustration
Phasor Summation Principle
I=X2+Y2I = \sqrt{X^2 + Y^2}I=X2+Y2тАЛ
Or, squared form:I┬▓ = X┬▓ + Y┬▓
тЬЕ

C is correct тАФ The equation I2=X2+Y2I^2 = X^2 + Y^2I2=X2+Y2 represents the Pythagorean relationship for the magnitude of a resultant phasor composed of two orthogonal components X and Y.

Core Concepts Used
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Phasor addition Orthogonal components Pythagorean theorem in A.C. circuits
ЁЯТб EXAM TIP

Always verify if the components are in phase or quadrature before applying addition rules; algebraic addition applies only to in-phase components.

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