Principle of virtual work Virtual displacement An imaginary displacement which is consistent with the constraint relation at a given instant (without allowing the real time to change) is called a virtual displacement. A virtual infinitesimal displacement δx i  = dx i   at dt = 0                                    δx i  = dx i  | dt=0  Virtual work The work done by any force on a particle due to its virtual displacement is called a virtual work. Thus for a system of particle in static equilibrium, the work done by all the applied forces should vanish, provided that the virtual work done by all the constraint forces vanishes. This is called the principle of virtual work. To know about this lecture in more detail please visit on  https://youtu.be/XubK3iz8vGY  or  https://youtu.be/ISZr-XySgHk

Power Electronic Systems The output of a power electronic converter circuit depends on the requirement of the load. Example If the load is a dc motor, then the output of converter must be an adjustable direct voltage. If the load is a 3-phase induction motor, then the converter may have adjustable voltage and frequency at its output terminals. In power electronic systems, the feedback component measures a parameter of the load and also compare it with the command. For example it measures the speed in case of a rotating machine. To know about this lecture in more detail please visit on https://youtu.be/Yfwi8uHUIxY

Advantage and Disadvantage of Power Electronics Advantage of Power electronics Power electronics is used in space shuttle power supplies Since there is very low loss in power electronic devices so its efficiency is very high. Power electronic converter systems are highly reliable. Since there is no moving parts in power electronic systems so it has long life and also its maintenance cost is very less. The power electronic systems has fast dynamic response in comparison to electromechanical converter systems. Since the power electronic system has small size and also it has less weight so they occupy less floor space and hence their installation cost is also less. Now these days power equipments are being mostly used, so power semiconductor devices are being produced on a large scale, resulting in lower cost of converter equipment. Power electronics are used in computer and office equipments. It is used in uninterruptible power supplies. Power...

Constraints and its classification Constraints force Constraints are restrictions that limit the motion of the particles of a system. Physically constrained motion is realized by the forces which arise when the object in motion is in contact with the constraining surfaces or curves. These forces are called constraint forces. Properties of constraints force They are elastic in nature and appear at the surface of contact. They are so strong that they barely allow the body under consideration to deviate even slightly from a prescribed path or surface. This prescribed path or surface is called a constraint. The effect of constraint force is to keep the constraint relations satisfied. Classification of constraints           Scleronomic and Rheonomic This classification is based on time. The constraints are said to be scleronomic constraints, if the constraint relations do not explicitly depend on time. But if the constraint rela...

Biasing of pn junction A  p-n junction can be connected to an external battery by two ways.  The method of connecting the p-n junction to an external battery is known as biasing.  There are two types of biasing, forward basing and reverses biasing.  Forward Bias If p terminal of a p-n junction is connected to positive terminal of an external battery, and n terminal of it is connected to negative terminal of battery then such type of biasing is known as forward bias. It is clear from the figure given below. In forward bias the current flowing in the circuit is due to majority charge carriers and therefore the  resistance is very small and hence the current flowing in the circuit is of the order of milli ampere. In forward biasing as we increase the potential across the junction, the value of current in the circuit increases very small initially, but after a certain value of potential the depletion region breaks due to high potential across the junction and the v...

Principle of phase control The simplest form of controlled rectifier circuit consists of a single thyristor feeding dc power to a resistive load R. An SCR can conduct only when anode voltage is positive and a gating signal is applied. It is found that a thyristor blocks the flow of load current until it is triggered. Since by varying the firing angle, the phase relationship between the start of the load current and supply can be controlled, hence the term phase control is used for such a method of controlling the load current. Since this circuit produces only one pulse of load current during one cycle of source voltage, so it is single phase half wave circuit. To know about the principle of phase control by using a simplest form of controlled rectifier circuit which includes a thyristor, a resistor and an a.c. source please see our latest video on https://youtu.be/5qwOYhAWHsU The wave pattern of gate current, load voltage, load current an...

Conservation laws Conservation of linear momentum Conservation of angular momentum Conservation of energy Conservation of linear momentum In the absence of external force (F), the total linear momentum of the system (p) always remain constant. It means if F = 0, then p = constant Conservation of angular momentum In the absence of external torque (), the total angular momentum of the system (L) always remain constant. It means if torque = 0, then L = constant Conservation of energy Energy can neither be created, nor be destroyed, it can only be convert from one form to another, it means the total energy of an isolated system always remains constant.

Determination of specific charge by Helical method Sample reading Accelerating voltage (V a ) Current in solenoid when a.c. voltage is applied to XX plate Current in solenoid when a.c. voltage is applied to YY plate 600 0.42 0.50 700 0.44 0.52 800 0.46 0.58 Note:   Above readings are only for reference, students should perform the practical in their laboratory and get their own readings.

Dear students you can get your physics practical assignment for the M.Sc. IV semester from here. The links of the notes of different practical objects are given below: Practical Physics II Object 1 Velocity of ultrasonic sound using ultrasonic interferometer... https://youtu.be/6VzY_BjVkms Object 2 Lande g factor for an electron https://cutt.ly/NmRtXwJ Object 3 Heat capacity of unknown metal... https://cutt.ly/CmT5ivJ Object 4 ... https://... Object 5 ... https://... Attendance link https://...

Microwave ferrites The ferrite is a high resistance magnetic material, which mainly consists of ferrite oxide along with one or more other metals. The ferrites are extremely useful at microwave frequencies. It is found that the electromagnetic waves pass through ferrites with negligible attenuation. Also these materials produce a phase shift in the electromagnetic wave propagation, which can be influenced by the applied dc magnetic fields. Applications of ferrite Ferrites are used at radio frequencies in inductors as core material. The ferrites are also used in cathode ray tubes (CRT) of TV. The ferrites are used in microwave isolators, circulators, and switches. Characteristics of ferrite The ferrites which are used at microwave frequency have the specific resistivity of the order of 10 12   Ω-cm. It is found that the relative permittivity of ferrites lie in the range of 5-20. To know more about this lecture plea...

Resonators Resonators It is found that any distributed transmission line of length λ g /2 will resonate, if it is shorted or open at one end. This is the principle of resonators . A resonator is actually a device or a system that exhibits resonance or resonant behaviour. It means it naturally oscillates at some frequencies with greater amplitude than at other frequencies. The frequencies at which the device oscillate are known as resonant frequencies . The oscillations produced in a resonator can be either electromagnetic resonance or mechanical resonance. The resonators are used to generate either waves of specific frequencies or to select specific frequencies from a signal. The musical instruments use acoustic resonators and it produce sound waves of specific tones. Resonance The resonance is a phenomenon that consists of a given system, which is driven by another vibrating system or by external forces to oscillate with greater amplitude at some particular ...

Grand canonical ensemble Grand canonical ensemble Microcanonical ensemble is a collection of independent assemblies in which energy (E), volume (V), and number of particles (N) remain constant. Canonical ensemble is a collection of independent assemblies in which temperature (T), volume (V), and number of particles (N) remain constant. It mean a microcanonical ensemble ⟶ Canonical ensemble, if we ignore the condition E = constant. Therefore the energy exchange takes place in this ensemble. Actually in chemical process, the number of particles N varies and it is very difficult to keep the number of particles constant in various phenomenon like radioactive decay process. Thus grand canonical ensemble is an ensemble in which the exchange of energy as well as the number of particles takes place with the heat reservoir. The grand canonical ensemble is a collection of essentially independent assemblies having the same temperature T, volume V, and a chemical potential µ....

Liquid helium as a Boson system Ordinary helium consists almost entirely of neutral atom of the isotope 2 He 4 . Since the total angular momentum of these atom is zero, so it follow the Bose-Einstein statistics. Properties of helium at low temperature The helium gas at atmospheric pressure condenses at 4.3K temperature into a liquid helium having critical temperature 5.2K, and the density of this liquid helium is very low (ρ = 0.124 g/cm 3 ). On further cooling the helium to about 0.82K, it does not freeze, and the liquid helium remains into liquid state up to absolute zero temperature i.e., T = 0K. It means the helium does not solidified at atmospheric pressure. To get the solid state of helium, it is subjected to an external pressure of at least 23atm. Phase transition of liquid He For He 4 in liquid phase, there is another phase transition (λ-transition), which divides the liquid state into two phases HeI and HeII. While liquefying He at...

Rectangular cavity resonator A rectangular cavity resonator is a piece of rectangular waveguide of dimension a, b, and c. In figure a rectangular cavity resonator of sides a, b, c is shown. TE waves in a rectangular cavity resonator Here we will consider about two transverse electric waves, out of two one moves in +z direction and another in -z direction. Let the transverse component of electric field for TE waves propagating along +z direction be This equation give the resonant frequencies for different sets of m, n, p for different cavity modes. If two or more independent cavity modes have the same resonant frequencies then it is known as degenerate frequency. It is found that the modes TE 000 , TE 001 , TE 010 and TE 100 do not exist in the cavity. The lowest modes (dominant mode), which are possible in TE mode are TE 101 , TE 011 etc. The allowed frequencies corresponding to dominant modes is fundamental frequency. To know more about...

Determination of size of lycopodium power by forming diffraction fringes Sample reading Table for first order diffraction ring Table for second order diffraction ring Note:   Above readings are only for reference, students should perform the practical in their laboratory and get their own readings.