Waves

Waves are everywhere. Sound waves, visible light waves, radio waves, water waves, microwaves, sine waves, cosine waves, earthquake waves, and slinky waves and are just a few of the examples of our daily encounters with waves.

 

Important basic characteristics

Important basic characteristics of waves are wavelength, amplitude, period, and frequency. Wavelength is the length of the repeating wave shape. Amplitude is the maximum displacement of the particles of the medium, which is determined by the energy of the wave. Wavelength represented by  the Greek letter lambda

 

Transverse waves

Transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

 

Longitudinal waves

Longitudinal waves the displacement of the medium is parallel to the propagation of the wave.

 

Speed of sound

The speed of sound in Air is 340 m/s .The speed of sound depends on the medium that the waves pass through, and is a fundamental property of the material. The speed varies depending on atmospheric conditions; the most important factor is the temperature Humidity has little effect on the speed of sound, nor does air pressure by itself Air pressure has no effect at all in an ideal gas approximation.

 

Resonance

The word resonance comes from Latin and means to ‘resound ‘to sound out together with a loud sound. Resonance is a common cause of sound production in musical instruments. When a sound or light wave strikes an object, it is already vibrating at some particular frequency. If that frequency happens to match the resonant frequency of the object it’s hitting, then you’ll get what’s called resonance. Resonance occurs when the amplitude of an object’s oscillations are increased by the matching vibrations of another object. If a second interconnected object or instrument vibrates or oscillates at that specified frequency then the first object can be forced to vibrate at a frequency higher that its natural harmonic frequency. This phenomenon is known as resonance.

 

Reverberation

The natural echo of a room is called reverberation. Reverberation is a measure of how much the sound is reflected around the room. Materials that are soft and uneven (like curtains, carpets and cushions) absorb sound much more than they reflect it, and decrease reverberation. Reverberation is the phenomenon of persistence of sound after it has been stopped as a result of multiple reflections from surfaces such as furniture, people, air etc. within a closed surface. These reflections build up with each reflection and decay gradually as they are absorbed by the surfaces of objects in the space enclosed.

 

Echo

A reflected sound can be heard separately from the original sound if the sound source is closer to the receiver while the reflecting hard surface is sufficiently far from receiver. Such reflected sound is called an echo. What is minimum distance for an echo to be produced? It’s Depends on the quality of the sound. The minimum distance to hear an echo will be partly based upon the observers ability to resolve different sounds. Assuming a sharp sound the minimum distance (d=vt) to hear distinct echo is 17m considering the speed of sound to be 340m/s.

 

Acoustics

Sound is the sensation caused in the ear by the vibration of the surrounding air or other medium. Noise is unwanted sound. When noise exceeds the permissible level, it causes various problems for the listeners. Ventilation and air-conditioning systems may also be a source of nuisance. Reverberation is particularly noticeable in cathedrals and other large buildings where multiple sound reflections can occur from walls, roof and floor. The characteristics of a building in relation to sound are called its acoustics, and the pioneer work in this field was carried out in the early twentieth century by Professor W. C. Sabine of Harvard University. Building acoustics concerns the level of acoustic comfort for the occupants of buildings. Acoustic and noise control plays a very important role in the design and construction of building-s.

Seismic waves

Recordings of seismic waves from earthquakes led to the discovery of the earth’s core and eventual maps of the layers of the Earth’s inside. Seismic waves travel fast, on the order of kilometers per second (km/s). The precise speed that a seismic wave travels depends on several factors, most important is the composition of the rock. Earthquakes generate three types of seismic waves: P (primary) waves, S (secondary) waves and surface waves, which arrive at seismic recording stations one after another. Both P and S waves penetrate the interior of the Earth while surface waves do not. Due to this, P and S waves are known as ‘body waves’.

 

joule’s law
The principle that the rate of production of heat by a constant direct current is directly proportional to the resistance of the circuit and to the square of the current.  When a current of I amperes passes through a circuit of resistance R ohms for a time of t seconds then the heat produced is given by the relation.
H=I2 Rt joules. The relation is known as the joule’s law of heating. It states that the heat produced is proportional to Square of the current I. Resistance of the circuit R.  The time t during which the current flows through the circuit.

Fuse
a fuse is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit. There are several different types of fuses.  The most common fuse used in homes is a circuit breaker. Circuit breakers are switches that open up to stop current in the event of an overload. They can be closed by the flip of a switch. Circuit breakers are common in homes, businesses and industrial services. The another is cartridge fuse. Cartridge fuses are held in place by spring clips and are easy to replace when necessary.

 

Different type of bulb

 

Incandescent bulbs
Application:Domestic use
Advantage: Direct connection without intermediate switchgear, Reasonable purchase price
Disadvantage: Low luminous efficiency and high electricity consumption, Significant heat dissipation, Short service life

Fluorescent tube
Application: Domestic , Shops, offices, workshops
Advantage: High luminous efficiency
Disadvantage: Low light intensity of single unit, Sensitive to extreme temperatures

LED
Application: Domestic, Shops, offices, Signaling ,emergency lighting
Advantage: Low energy consumption, Low temperature, long service life
Disadvantage: Low brightness of single un-ti

 

Arc lamps

 

Arc lamps are a category of lamps that produce light by an electric arc also known as a voltaic arc. The lamp consists of two electrodes that are separated by a gas. The lamp is named based on the type of gas that is used in the arc.

Electromagnetic induction

Electromagnetic induction is a process where a conductor placed in a changing magnetic field causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current - it is said to induce the current. Michael Faraday is given credit for the discovery of electromagnetic induction in 1831.

 

AC and DC generators

Generators use electromagnetic induction to convert mechanical energy into electrical energy. In an AC, or alternating current, generator, the electrical current periodically reverses direction. With a DC, or direct current, generator, the current flows only in one direction. There are several other primary differences between AC and DC generators Both AC and DC generators produce currents via electromagnetic induction. AC and DC generators serve different purposes. Homes typically use AC generators to power small motors and common electrical appliances. DC generators power very large electric motors — such as those needed for subway systems. Moreover, DC generators provide a reliable and efficient energy supply. The AC generator produces variable output voltage in term of amplitude and time. For some instance. The DC generator produces constant output voltage in term of amplitude and time. In AC generator uses slip ring and brush. Here does not use of commutator   In DC generator uses commutator and brushes. A split-ring commutator makes the current change direction every half-rotation, whereas a slip-ring commutator merely maintains a connection between the moving rotor and the stationary stator. Slip rings are useful for DC motors where the current has to change direction every half revolution whereas split rings are used to make constant current connection to a commutator, which is what you want for an AC motor.

 

Mutual induction

Mutual induction is a phenomenon when a coil gets induced in EMF across it due to rate of change current in adjacent coil in such a way that the flux of one coil current gets linkage of another coil.

 

Electrical power transformer

A transformer makes use of Faraday’s law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages. Electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings. It transforms power from one circuit to another without changing its frequency but may be in different voltage level.

 

self-induction

When the electric current in a coil changes, the magnetic flux linked with that coil also changes. Consequently, an emf is induced in the coil. This type of induction is called self-induction and the induced emf is called back emf.

 

Inductor

An Inductor is nothing more than a coil of wire wound around a central core. An inductor typically consists of an electric conductor, such as a wire, that is wound into a coil. An inductor also functions as a low-pass filter since fast-changing signal currents are not stable long enough to overcome the reverse EMF (electro-motive force) that the inductor generates in response to a change in current. An inductor that is magnetically coupled with another inductor is a transformer and this allows an alternating signal to induce another alternating signal magnetically with no actually electrical connection.

 

Power transmission and distribution losses

Electric power transmission and distribution losses refer to the losses that occur in transmission between the sources of supply and points of distribution, In other words, the loss of power that arises due to the inherent resistance and transformation inefficiencies in the electrical conductors and distribution transformers respectively are called transmission and distribution losses.

Remember
The earth pin is thicker and longer than the other two pins.
The basic unit of electricity is kilowatt hour.
in thermal power station heat energy is converted to electric power