AC circuits Flashcards
What is a capacitor?
A capacitor is formed from two conducting plates separated by a thin layer called dielectric.
How does a capacitor work?
If a current (i) flows, positive charge (q) accumulates on the upper plate, while a balancing negative charge is present on the lower plate.
What is the formula for potential energy difference (voltage) in a capacitor?
v = d / (Aε) * q
What does capacitance measure?
Capacitance is the ability of the capacitor to store electric charges.
What is the relationship between capacitance (C), charge (q), and voltage (v)?
C = q / v
What is the unit of capacitance?
Farad (F)
What is the formula for capacitance of a parallel-plate capacitor?
C = (ε0εrA) / d
What do ε0 and εr represent in the capacitance formula?
ε0 is the absolute permittivity of free space, and εr is the relative permittivity of the dielectric material.
What is the capacitance of a multi-plate capacitor with uniform dielectric?
C = (ε0εrA) / d * (n - 1)
What is the formula for capacitance of a multi-plate capacitor with different dielectrics?
C = (d1 / (εr1 + εr2 + εr3)) * (ε0A / d2)
What is the characteristic of capacitors connected in series?
The total charge (Qt) is equal across all capacitors: Qt = Q1 = Q2 = … = Qn.
What is the voltage relation for capacitors in series?
The total voltage (Vt) is the sum of individual voltages: Vt = V1 + V2 + … + Vn.
What is the capacitance relation for capacitors in series?
1 / Ct = 1 / C1 + 1 / C2 + … + 1 / Cn.
What is the characteristic of capacitors connected in parallel?
The total voltage (Vt) is equal across all capacitors: Vt = V1 = V2 = … = Vn.
What is the capacitance relation for capacitors in parallel?
Ct = C1 + C2 + … + Cn.
What is an inductor?
An inductor is a passive electrical component that stores energy in its magnetic field.
What is the current relation for inductors in series?
The current (i) is the same through all inductors: di/dt = di1/dt = di2/dt = … = din/dt.
What is the voltage relation for inductors in series?
Vt = V1 + V2 + … + Vn.
What is the inductance relation for inductors in series?
Lt = L1 + L2 + … + Ln.
What is the current relation for inductors in parallel?
di/dt = di1/dt + di2/dt + … + din/dt.
What is the voltage relation for inductors in parallel?
Vt = V1 = V2 = … = Vn.
What is the inductance relation for inductors in parallel?
1 / Lt = 1 / L1 + 1 / L2 + … + 1 / Ln.
What is reactance in AC circuits?
Reactance is the non-resistive component of impedance, arising from inductance or capacitance.
What is impedance in AC circuits?
Impedance is the effective resistance of an electric circuit to alternating current, combining ohmic resistance and reactance.
In a capacitor, current leads voltage by how many degrees?
90 degrees.
In an inductor, voltage leads current by how many degrees?
90 degrees.
What does the term ‘in-phase’ mean in AC circuits?
Voltage and current reach their zero, peak, and valley points at the same time.
What is Euler’s identity?
e^(j(ωt + φ)) = cos(ωt + φ) + j sin(ωt + φ)
What does the phase angle (φ) represent?
The phase angle in degrees or radians.
What is the formula for angular frequency (ω)?
ω = 2πf
What is the relationship between frequency (f) and period (T)?
T = 1/f
What is the rms value of a current?
The effective value of an alternating current.
What happens when AC voltage is applied across pure resistance?
It draws a current that is in-phase with the AC voltage.
What happens when AC voltage is applied across pure inductance?
It draws a current that lags the AC voltage by 90 degrees.
What is the current behavior in a pure inductance when AC voltage is applied?
The current lags the AC voltage by an angle of 90°.
In the formula ( X_L = 2pi f L ), what does each symbol represent?
- ( X_L ) = inductive reactance, ohms
- ( f ) = frequency, Hertz (Hz)
- ( L ) = inductance, Henry (H)
What occurs when an AC voltage is applied across pure capacitance?
The current leads the AC voltage by an angle of 90°.
What is the formula for capacitive reactance?
The formula is ( X_C = rac{1}{2pi f C} ).
In a series R-L circuit, how does the current behave with respect to the AC voltage?
The current lags the AC voltage with an acute angle Ɵ.
What is the formula for total impedance in a series R-L circuit?
The formula is ( Z = sqrt{R^2 + X_L^2} ).
What happens in a series R-C circuit when an AC voltage is applied?
The current leads the AC voltage with an acute angle Ɵ.
What is the behavior of current in a series L-C circuit?
The current can either lag or lead with the AC voltage by an angle of 90°.
In a series R-L-C circuit, how does the current behave?
The current can either lag, lead, or be in-phase with the AC voltage.
What is the formula for total impedance in a series R-L-C circuit?
The formula is ( Z = sqrt{R^2 + (X_L - X_C)^2} ).
What is the relationship for total impedance in a series circuit?
The total impedance ( Z_t = Z_1 + Z_2 + … + Z_n ).
What is the formula for total impedance in a parallel circuit?
The formula is ( rac{1}{Z_t} = rac{1}{Z_1} + rac{1}{Z_2} + … + rac{1}{Z_n} ).
What is the basis of nodal analysis in AC circuits?
The basis is Kirchhoff’s current law (KCL).
What forms the basis of mesh analysis?
Kirchhoff’s voltage law (KVL) forms the basis.
Fill in the blank: In a series R-C circuit, the total impedance is given by ( Z = sqrt{R^2 + ______^2} ).
X_C
True or False: In a series L-C circuit, the current is always lagging.
False
What does KCL stand for?
Kirchhoff’s Current Law.
What does KVL stand for?
Kirchhoff’s Voltage Law.
What angle does the current lag in a series R-L circuit?
The current lags with an acute angle Ɵ.
What angle does the current lead in a series R-C circuit?
The current leads with an acute angle Ɵ.
What is the impedance in a series circuit with an inductive reactance of 8 Ω and a capacitive reactance of 18 Ω connected in parallel?
The total impedance is 16.62 Ω.
What is the impedance of a circuit with resistance R and inductive reactance X_L?
The impedance ( Z = sqrt{R^2 + X_L^2} ).
What is the value of inductance that causes a current of 2 A lagging in a series L-C circuit?
The value of inductance must be calculated based on the circuit parameters.
