TECHNOLOGIES

Structurally and construction wise a direct current motor is exactly similar to a DC generator, but electrically it is just the opposite. Here we unlike a generator we supply electrical energy to the input port and derive mechanical energy from the output port. We can represent it by the block diagram shown below.

Here in a DC motor, the supply voltage E and current I is given to the electrical port or the input port and we derive the mechanical output i.e. torque T and speed ω from the mechanical port or output port.

The input and output port variables of the direct current motor are related by the parameter K.

So from the picture above we can well understand that motor is just the opposite phenomena of a DC generator, and we can derive both motoring and generating operation from the same machine by simply reversing the ports.

Secrets behind the rotation:

According to Faraday’s law an emf induced in any circuit is due to the rate of change of magnetic flux linkage through the circuit. As the rotor winding in an induction motor are either closed through an external resistance or directly shorted by end ring, and cut the stator rotating magnetic field, an emf is induced in the rotor copper bar and due to this emf a current flows through the rotor conductor.

Here the relative velocity between the rotating flux and static rotor conductor is the cause of current generation; hence as per Lenz's law the rotor will rotate in the same direction to reduce the cause i.e. the relative velocity.

Thus from the working principle of three phase induction motor it may observed that the rotor speed should not reach the synchronous speed produced by the stator. If the speeds equals, there would be no such relative velocity, so no emf induction in the rotor, & no current would be flowing, and therefore no torque would be generated. Consequently the rotor can not reach at the synchronous speed. The difference between the stator (synchronous speed) and rotor speeds is called the slip. The rotation of the magnetic field in an induction motor has the advantage that no electrical connections need to be made to the rotor.

Thus the three phase induction motor is:

• Self-starting.

• Less armature reaction and brush sparking because of the absence of commutators and brushes that may cause sparks.

• Robust in construction.

• Economical.

• Easier to maintain.

Young people are experiencing depression, anxiety, and sleep deprivation because they feel a constant need to be on social media sites 24x7, according to new research.

Professors from the University of Glasgow questioned over 460 respondents aged between 11 and 17 regarding their overall -- but specifically night-time -- social media use, and also measured sleep quality, self esteem, and emotional investment in the sites.

Results showed how a constant need to make them selves available online was making teens feel tired down, and anxious as they struggled to keep in-the-loop with what was happening on the internet.

One of the researchers, Dr Heather Cleland Woods, described how adolescence can be a period of in creased vulnerability for the onset of depression and anxiety, with poor sleep quality contributing to this. She said: "Evidence is increasingly supporting a link between social media use and wellbeing -particularly during adolescence -but the causes of this are unclear."

Motorcycle engines may be two-stroke or four-stroke internal combustion engines, but other types have been used in small numbers. The engine typically drives the rear wheel. Most engines have a gearbox with two to six ratios, reverse gear is rare but does exist for sidecar use. Power is sent to the driven wheel by belt, chain or shaft. In Europe, before the 1969 Honda CB750 engine capacities  typically ranged from about 50 cc to 750 cc; but since then machines with capacities up to 2,300 cubic centimetres (140 cu in) Triumph Rocket 3  have become common. In the USA, motorcycles with large capacities have been common for much longer. 

Working vedio:

https://www.youtube.com/watch?v=fNcZDrfT498

The Lenovo IdeaPad Yoga 13 is a convertable laptop created by Lenovo and first announced at the International CES 2012 in January. The Yoga 13 gets its name from its ability taken on various form factors due to its screen being mounted on a special two-way hinge.

The name "Yoga" is a reference to the unit's design that makes use of a double hinge to allow four different configurations in order to provide maximum flexibility to the user.

The Yoga 13 is 17mm thick. The Yoga's hybrid design was achieved through the use of a special patented hinge that allows the keyboard to flip flush to the back of the display. The Yoga 13’s hinge allows the device to be held partway open so it can be set upright on a flat surface as a display. When the keyboard is folded away the computer functions as a touch-controlled tablet. Much of the Yoga 13's usability as a tablet is made possible through Microsoft's windows 8

The HTC One (codenamed and retroactively called ME) is a touch screen based Android smartphone designed, developed, and manufactured by HTC. The smartphone was unveiled on 19 February 2013, at press events in New York City and London and is HTC’s seventh flagship smartphone. It is the successor to the company’s 2012 flagship model, the One X—which was critically acclaimed, but commercially unsuccessful due in part to insufficient marketing efforts. To make the device stand out among its competition, the HTC One was developed with a major emphasis on unique hardware and software features; which included aunibody aluminum frame, a 1080p full-HD display, dual front-facing stereo speakers, a camera with a custom image sensor and the ability to automatically generate montages of media, an updated version of HTC’s Sensor user experience, BlinkFeed—anaggregatorof news and social network content, and an electronic program guide app with the ability to serve as a universal remote via an IR blaster located in the device’s power button.