Residual current

In the electrical circuits residual current is the electrical current which flows in a circuit when  the voltage is reduced to zero.

Somewhere it is called fault current. It is seen in the circuit, sometimes when we switch off the line then we got shocked while touching it. this is due to the residual current. Also we can realize that the wire is a little bit heated when we make voltage  suddenly to zero.

The main reason behind is the charge carriers ie; electrons. When the electrons are steadliy drifting in conductor wire it acquires current in the opposite of the motion of electrons. When the potential is reduced to zero instantaneously the voltage across the circuit becomes zero. In common sense there is no flow of electrons, but the drifting electrons have momentum because it has its own mass and velocity. At a instant time if it find ground or low potential it will recently discharge or earthen. If it don't get the way to flow the electrons having some momentum will collide with atoms in conductor and change their kinetic energy to heat energy. As we feel the wires hotter when we suddenly switch off.

It has also reverse process, when the wire is heated at zero voltage the free electrons in the conductor gain energy and start to flow on their favourable way, which is also called fault current. 

These type of effect could cause harmful disaster in the area of use so safety measures are also used to control these problems in electronics and electrical mercenaries. Residual current circuit breaker, sensors etc are used to defeat these problems.

Why to use N95 mask? Science behind the scene.

To preserve from pendemic disease, airborne particles we use mask.In current situation: Due to covid-19 doctors and experts recommend to wear N95 mask because it can filter 95% including big particles to nano particle. The thread is charged to attract nano particles and high filtration quality so it is very specific than other masks.

Filteration mechanisms of N95 mask

• Inertial impaction: With this mechanism, particles having too much inertia due to size or mass cannot follow the airstream as it is diverted around a filter fiber. This mechanism is responsible for collecting larger particles.
• Interception: As particles pass close to a filter fiber, they may be intercepted by the fiber. Again, this mechanism is responsible for collecting larger particles.
• Diffusion: Small particles are constantly bombarded by air molecules, which causes them to deviate from the airstream and come into contact with a filter fiber. This mechanism is responsible for collecting smaller particles.
• Electrostatic attraction: Oppositely charged particles are attracted to a charged fiber. This collection mechanism does not favor a certain particle size.
  

In all cases, once a particle comes in contact with a filter fiber, it is removed from the airstream and strongly held by molecular attractive forces. It is very difficult for such particles to be removed once they are collected. As seen in Figure 2, there is a particle size at which none of the “mechanical” collection mechanisms (interception, impaction, or diffusion) is particularly effective. This “most penetrating particle size” (MPPS) marks the best point at which to measure filter performance. If the filter demonstrates a high level of performance at the MPPS, then particles both smaller AND larger will be collected with even higher performance.

This is perhaps the most misunderstood aspect of filter performance and bears repeating. Filters do NOT act as sieves. One of the best tests of a filter’s performance involves measuring particle collection at its most penetrating particle size, which ensures better performance for larger and smaller particles. Further, the filter’s collection efficiency is a function of the size of the particles, and is not dependent on whether they are bioaerosols or inert particles.

Reference;Niosh science.

Alternate magnetic field of earth

Magnetic effect of electric current is one of the major effects which functions as the basic principle in appliances used in various fields of activities. The magnetic field around a current carrying conductor can be depicted by using magnetic field lines which are represented in the form of concentric circles around it. The direction of magnetic field through a current carrying conductor is determined by the direction of flow of electric current.

In case of earth the magnetic field, it is generated you electric currents due to the motion of convection currents of a mixture of molten iron and nickel in the Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo. Which is on the way from centuries.

From different research and data it is found that the earth magnetic field is collapsing. The north and south pole are shifting from initial position.

 Earth's present-day magnetic field is, in fact, much stronger than normal. The dipole moment, a measure of the intensity of the magnetic field, is now 8 × 1022 amps × m2. That's twice the million-year average of 4× 1022 amps × m2.

To understand what's happening, says Glatzmaier, we have to take a trip ... to the center of the Earth where the magnetic field is produced.

At the heart of our planet lies a solid iron ball, about as hot as the surface of the sun. Researchers call it "the inner core." It's really a world within a world. The inner core is 70% as wide as the moon. It spins at its own rate, as much as 0.2° of longitude per year faster than the Earth above it, and it has its own ocean: a very deep layer of liquid iron known as "the outer core

." 

It takes billions of years to alternate the position of North and South pole. Noone knows exactly that why the magnetic field of earth flip flop.

What is your opinions on this content ?………

Superconductor and its reality.

The superconductor which we heard is the type of conductor having negligible or about to zero resistance. The pure superconductor in is not found freely in nature. When the substance is cooled less then or equal to critical temperature it behaves like a superconductor as we know about Mercury(Hg).

As we all know that in superconductor the resistance is negligible or you can say that no resistance. According to our theory in superconductor the energy gap between valence band and conductance band is negligible because these two band are very closed to each other i.e the electron of valence band can go freely in conductance band and similarly converse is also true.And finally these band will be become a single band in which electron can move freely

The great misconceptions is that, when we use superconductor instead of Conductor and passed electric charge with help of electric field for a second, the light bulb doesn't off for long lasting.the thing to be noted is that the superconductor doesn't acquire any resistance ideally. But when we use light bulb it will provide some resistance to glow, since we can make the light glowing(for some more time) after electric field is stopped. It is because the resistance offered by light can deaccelerate the electron through the bulb, By deaccelerating the electrons results to stop the moving electrons.

  

If you have any suggestions please drop on the comment section below.

Do you know the secret of turmeric?

Yes, the turmeric basically being used in every dish for colour (yellow) and smell . Without its presence the food is not satisfying for our eyes. 

Chemical background

Turmeric (Curcuma longa) is used as spice, preservative, colouring matter and has wide range of medicinal and pharmacological applications. It exhibits anti-inflammatory, anti-HIV, anti-bacterial, antioxidant, nematocidal, antiparasitic, antispasmodic and anticarcinogenic activities. It is a potent scavenger of a variety of reactive oxygen species (ROS) including superoxide anion, hydroxyl radical, singlet oxygen, peroxynitrite and nitric oxide. It is a inhibitor of ROS generating enzymes, cyclooxygenase and lipoxygenase and plays active role in the inhibition of COX-I and COX-II enzymes that are involved in the inflammatory reaction. The turmeric extract protects lipids, haemoglobin, and red blood cells from lipid peroxidation induced by hydrogen peroxide.  

Did you ever notice the turmeric also behave like indicator as we use phenolphthalein, methyl orange, litmus paper and so on to identify whether substance is acidic, basic or neutral by their change in colour. Termeric powder has its own property that, when it is kept contact with basic subsistences in aqueous form the original yellow colour changes to pink red.   As we make the solution of turmeric powder and mixed it with some sodium hydroxide solution the colour change occured. Also we experimented on both strong and weak base from potassium hydroxide to ash. Though it couldn't be use for acidmetry but efficient to know whether the substance is acidic or basic by its colour change.

In case of acid ,it doesn't respond physically so there is no change in colour with acids.

Since turmeric is only an indicator for base.

For any suggestions leave a comment below.

Thermocouple and its basic principle

Thermocouple is the device which is made up of combination of two different material (wires) in the specific circuit. It's main significance is that the junction points show the surprising behaviour in the closed circuit.

Principle

The principle of thermoelectric effect(caused by the thermocouple in the circuit) is that when we connect the two different wires like as copper and iron . If electric charge is passed through it in the specific direction ie;copper to iron, as in the figure. We find that the one junction get hotter and another junction begins to cool . That is the result of thermoelectric effect. As we know metals like iron, copper,silver etc has different free electron density. We know the fact that iron contains more free electron density than that of copper metal. When both wire are connected, there will form two junctions with high free electron density to low free electron density and vice versa ie,from iron to copper and vice versa. When electric field in a specific direction is applied the electricity passes through both junctions. In the junction when field passes through iron to copper the junction starts to get hot. Spontaneous process are from high to low ,when electric field is passed through iron to copper junction due to high electron density electrons passes to low electron density ie copper so there is not energy absorbed by surrounding but also heated by the kinetic energy of electrons so that results to heat the junction.

When the electricity is passed from copper to iron junction ,(lower electron density to higher electron density) the process is non spontaneous process so to pass electrons from lower density to higher it needs some energy which it gains by the surrounding, that phenomenon result to make junction cold.

By the complete closed circuit we can get one hot and another cold junction. That can be used in several devices, equipments and accessories.

The lightest electromagnetic shielding material

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic components or the transmission of signals. High-frequency electromagnetic fields can only be shielded with conductive shells that are closed on all sides. Often thin metal sheets or metallized foils are used for this purpose. However, for many applications such a shield is too heavy or too poorly adaptable to the given geometry. The ideal solution would be a light, flexible and durable material with extremely high shielding effectiveness.

Aerogels against electromagnetic radiation

A breakthrough in this area has now been achieved by a research team led by Zhihui Zeng and Gustav Nyström. The researchers are using nanofibers of cellulose as the basis for an aerogel(lightest solid), which is a light, highly porous material. Cellulose fibers are obtained from wood and, due to their chemical structure, enable a wide range of chemical modifications. They are therefore a highly popular research object. The crucial factor in the processing and modification of these cellulose nanofibres is to be able to produce certain microstructures in a defined way and to interpret the effects achieved. These relationships between structure and properties are the very field of research of Nyström's team at Empa.

The researchers have succeeded in producing a composite of cellulose nanofibers and silver nanowires, and thereby created ultra-light fine structures which provide excellent shielding against electromagnetic radiation. The effect of the material is impressive: with a density of only 1.7 milligrams per cubic centimeter, the silver-reinforced cellulose aerogel achieves more than 40 dB shielding in the frequency range of high-resolution radar radiation (8 to 12 GHz) - in other words: Virtually all radiation in this frequency range is intercepted by the material.

Ice crystals control the shape

Not only the correct composition of cellulose and silver wires is decisive for the shielding effect, but also the pore structure of the material. Within the pores, the electromagnetic fields are reflected back and forth and additionally trigger electromagnetic fields in the composite material, which counteract the incident field. To create pores of optimum size and shape, the researchers pour the material into pre-cooled molds and allow it to freeze out slowly. The growth of the ice crystals creates the optimum pore structure for damping the fields.

With this production method, the damping effect can even be specified in different spatial directions: If the material freezes out in the mold from bottom to top, the electromagnetic damping effect is weaker in the vertical direction. In the horizontal direction—i.e. perpendicular to the freezing direction—the damping effect is optimized. Shielding structures cast in this way are highly flexible: even after being bent back and forth a thousand times, the damping effect is practically the same as with the original material. The desired absorption can even be easily adjusted by adding more or less silver nanowires to the composite, as well as by the porosity of the cast aerogel and the thickness of the cast layer.

The lightest electromagnetic shield in the world

In another experiment, the researchers removed the silver nanowires from the composite material and connected their cellulose nanofibres with two-dimensional nanoplates of titanium carbide, which were produced using a special etching process. The nanoplates act like hard "bricks" that are joined together with flexible "mortar" made of cellulose fibers. This formulation was also frozen in cooled forms in a targeted manner. In relation to the weight of the material, no other material can achieve such shielding. This ranks the titanium carbide nanocellulose aerogel as by far the lightest electromagnet