Alternating Current Flashcards
(29 cards)
What is Alternating Current?
The current whose magnitude and direction changes with time and attains the same magnitude and direction after a definite time interval.
What is the instantaneous value of AC?
The instantaneous value of AC is -
I = I₀sinωt
[ ω = 2π/T = 2πv ]
What are the advantages of AC over DC?
- AC generation is easy and economical.
- It can be easily converted into DC.
- In AC, energy loss is minimum, so it can be transmitted over large difference.
What are the advantages of DC over AC?
- Ac shock is attractive while DC shock is repulsive.
- AC is more dangerous than DC.
- AC cannot be used for electroplating process because here constant current is needed.
What is Alternating Voltage?
The voltage whose magnitude direction changes with time an attains the same magnitude and direction after a definite time interval.
What is the instantaneous value of Alternating emf?
E = E₀sinωt
What is the root mean square of value of AC?
It is the value of constant current which would produce the same amount of heat in a given resistance in a given time as is produced by the AC through the same resistance at the same time during the complete cycle.
Iᵣₘₛ = I₀/√2
Iᵣₘₛ = 70.7% of I₀
What is the average current value of AC?
It is defined as the steady value of current which sends the same charge through a given circuit in the half cycle as given by the AC in the same circuit for the same interval of time.
Iₐᵥ = 2I₀/π
Iₐᵥ = 63.7% of I₀
What are Phasor Diagrams?
A diagram representing alternating current and emf as rotating vectors with the phase angle between them.
AC through Inductor?
An inductor with self-inductance is connected to an AC source with instantaneous emf.
What is AC through a Resistor?
Zero phase difference between instantaneous alternating current and emf.
What is AC through a Capacitor?
In a perfect capacitor, the current leads the voltage by a phase angle of π/2 radians or the voltage lags behind the current by a phase angle of π/2 radians.
Why do capacitors block DC?
The emf of the capacitor becomes the same as the source which ends the potential difference, stopping the flow of current.
What is Inductive Reactance?
The opposing nature of the inductor to the flow of alternating current.
Xₗ = ωL
What is Capacitive Reactance?
The opposing nature of the capacitor to the flow of alternating current.
X꜀ = 1/2πvC
What is AC through the L-C-R circuit?
An inductor, a capacitor, and a resistor are connected in series.
Z = E₀/I₀ = √R + (Xₗ - X꜀)²
What is an Impedance?
It is the total resistance of a circuit applied in the path of alternating current.
What happens when Xₗ = X꜀?
Voltage and current are in the same phase. So, the AC circuit is non-inductive.
What happens when Xₗ > X꜀?
Voltage leads the current by a phase angle Ø. Therefore, the AC circuit is an inductance-dominated circuit.
What happens when Xₗ < X꜀?
Voltage lags the current by a phase angle Ø. Therefore, the AC circuit is a capacitance-dominated circuit.
What is a steady-state solution?
Any arbitrary value of t and draw different phasors which shows the relative angle between different phasors. The solution so obtained is called a steady-state solution.
What is Resonance?
In a series L-C-R circuit, when the phase between current and voltage is zero, the circuit is said to be a resonant circuit.
What is called resonant frequency?
The frequency at which Xₗ and X꜀.
Vᵣ = 1/2π√LC
What is the average power associated with an AC Circuit?
Average power is defined as the rate of doing work.
Pₐᵥ = EᵣₘₛIᵣₘₛcosØ
