Types of AC Circuits
There are three types of AC Circuits :
- Purely Reactive
- Purely Capacitive
- Purely Inductive
Purely Reactive
A purely resistive circuit has a very negligible amount of inductance such that the reactance offered by such circuits is very small when compared to the resistance even at normal frequency.
V=Vmsin(ωt)
The current flowing through the purely resistive circuit can be derived as
I=VR
=VmRsin(ωt)
I=Imsin(ωt)
Purely Capacitive
The circuit containing only a pure capacitor of capacitance C farads is known as a Pure Capacitor Circuit. The capacitor works as a storage device, and it gets charged when the supply in ON and gets discharged when the supply is OFF.
The equation of the alternating voltage that is applied across the circuit is
V =Vmsinωt (1)
At any point in time, let the charge of the capacitor be
q =CV (2)
The current flowing through the purely capacitive circuit is given by:
i =dq/dt
Substituting (2) in the above equation,
i =d(CV) (3)
i =d (CVmsinωt)/dt
=CVm ˟ d(sinωt)/dt
i =ωCmcosωt=Vm ˟ ωC ⨯ sin(ωt+π2)
i =VmXcsin[ωt+π/2] (4)
where is Xc=1/ωC
Current will be maximum when sin(ωt+π/2)=1 . Hence,
Im =VmXc
On substituting this in (4) we get,
i =Imsin(ωt+π2)
Purely Inductive
The circuit which contains only inductance (L) and not any other quantities like resistance and capacitance in the circuit is called a Pure inductive circuit. In this type of circuit, the current lags behind the voltage by an angle of 90 degrees.
The equation of the alternating voltage that is applied across the circuit is
V=Vmsinωt (1)
This results in current flow along with an induced emf given by
e=−L(di/dt)
Since the induced emf is equal and opposite to the applied voltage,
V=−(−L⨯(di/dt))
Vmsinωt=L(di/dt)
dI=VmLsinωtdt (2)
Integrating both sides of (2) we get,
I =VmωLsin(ωt−π2)
=VmXLsin(ωt−π2) (3)
where XL is the opposition offered by pure inductance to the flow of alternating current and is called inductive reactance.
The maximum current will be when sin(ωt−π2)=1
Im=VmXL (4)
Substituting (3) in (4) we get,
I=Imsin(ωt−π/2)
Working Principles of Alternating Current Generator
Do you ever wonder what kind of current flows in the power lines of our household? Is it the same current that is generated in electronic devices with DC battery supply or is it something different? In this article, we will discuss a different current that alternates i.e. varies in magnitude and direction. This type of current is called alternating current.
Alternating current is generally seen flowing in power lines(telephone cables, office lines) and normal household electricity that comes from a wall outlet. It is basically used for industrial, chemical, and domestic power usage where it is transmitted over a long distance. The most common frequency for AC power in many parts of the world is 50 or 60 hertz (Hz), meaning the direction of the current changes 50 or 60 times per second. On the contrary, we have DC current which flows in one direction and doesn’t change polarity.
In this article, we will see all the terminologies related to AC current, the method used for generating AC current, and the difference between AC and DC current. We will also discuss the phasors and the application of AC currents. The later part of this article will talk about AC circuit analysis.