It is a known fact that from the scattering of α – particles, scientist Rutherford concluded that the atom of any element consists of central core called nucleus and electrons moving around it. The entire mass of the atom and positive charge is concentrated inside the nucleus. The nucleus is supposed to consist of two particles, the proton and the neutron. Their masses are nearly the same as : Continue reading “Parts of nucleus”
A rectifier is a device that converts alternating current into direct current.
Half wave rectifier:
In this rectifier, the PN junction diode is connected to an input AC supply with the help of a primary coil, which will induce an emf in the secondary coil and ultimately the output is taken across the load resistance (RL).
Let at any instant S1 is positive and S2 is negative. Due to this polarity the junction diode is forward biased so it will start conducting and output is obtained. Continue reading “Half wave rectifier operation”
There are four major modes that the waves transmitted from a transmitter may follow to reach the destination and they are
(a) Surface wave propagation
(b) Space wave propagation
(c) Troposphere propagation
(d) Ionosphere propagation. Continue reading “Modes of wave propagation”
Let us derive the relation of electric field intensity at finite distance from transmitter Antenna
If a horizontal Hertzian dipole antenna is used as a transmitter antenna above the horizon, then energy will travel like a wave in free space. Therefore, the amplitude of electric field vector in the radiation field can be given as : Continue reading “Electric field intensity at finite distance from transmitter Antenna”
Today we will discuss a very important relation related to wave propagation. The equation is known as Friis free space equation.
As only a small fraction of radiated power is received at the receiver from an isotropic radiator in free space, but the received signals, must be 10-20 dB above the receiver noise to complete the link between transmitter (TX) and receiver (RX) antenna. The amount of received power depends on transmitted power, gains of transmitter and receiver antennas and separation between them, operating frequency and path attenuation. Thus in order to describe the characteristics of wave propagation, it is necessary to derive equation relating to these parameters. The expression relating these parameters is known as Friis free space wave equation. Continue reading “FRIIS FREE SPACE EQUATION”
When a radio wave is radiated from the transmitting antenna, it spreads in all directions with decrease in amplitude with increasing distance because of spreading of the electromagnetic energy through larger surface areas and it follows inverse square law. This law states that the intensity of the radiating waves is inversely proportional to the square of the distance from the radiator.
Electromagnetic wave in the frequency spectrum of 0.001 to 1016 Hertz are termed as radio waves, but broadly speaking by radio waves, in this chapter, mean that band of electromagnetic energy which covers the frequency range from few kHz.
In a PN junction diode holes are the majority carriers on P side whereas electrons are the majority carriers on n-side. The process of diffusion takes place due to which the majority carriers diffuse from one region to the other so the P-region becomes less positive and the n-region becomes less negative.
An imaginary battery is developed across the junction which prevents further movement of majority carriers and the voltage so developed is known as the potential barrier. The layer is known as the depletion layer. Continue reading “How depletion layer or potential barrier is formed in the PN junction diode”