357. Q. & A.s SCI. & TECH. – 21

Q. &  A.s  ‑‑‑  SCI.  &  TECH. – 21

575Q. What devices are connected by Bluetooth?

        Bluetooth provides a secure way to connect and exchange information between devices such as

1.      Faxes,                                  

2.      Mobile phones,        

3.      Telephones,  

4.      Laptops,       

5.      personal computers,

6.      Printers,                   

7.      Digital cameras        

8.      Global positioning system (gps) receivers, and

9.      Video game consoles.

576Q. Why is it easier to remember words of a song than those of a paragraph?

Words of a paragraph

1.      We read the text of a paragraph and grasp the contents of it

2.      We should know reading and writing for this

3.      We should know grammatical rules

4.      Sentences cannot be remembered for ever.

Words of a song

1.      Song on the other hand carries both a meaning s well as a beauty of meaning

2.      There is rhyme and rhythm

3.      Even if language is not understood, the style of presentation attracts

4.      The words are concise

5.      Sense is more important than grammatical rules

6.      The language is simpler than the text matter

7.      Even if the words do not have meaning, the humming, the stress, …attract us

8.      A song can be remembered for ever

9.      That was why in olden days things were taught in a rhythmic manner.

Words in songs are usually simple and subtle whereas those in sentences are likely to be complex and big.

577Q. Why there are more Swamijis than Scientists in India?

1.      Indians are more religious minded.

2.      They believe in magic than logic.

3.      Self Exploitation and hypocrisy

4.      More fatalist than pragmatist

That is why there are at least 3 crore sadhus, Swamijis, foretellers, etc.

No Indian ever ruled India.

578Q. What is the effective range of Bluetooth?

        The effective range of Bluetooth varies due to

1.      propagation conditions,

2.      material coverage,

3.      production sample variations,

4.      antenna configurations and

5.      battery conditions.

579Q. List out the applications of Bluetooth.

A typical Bluetooth mobile phone headset.

·Wireless control of and communication between a mobile phone and a handsfree headset. This was one of the earliest applications to become popular.

·Wireless control of and communication between a mobile phone and a Bluetooth compatible car stereo system

·Wireless Bluetooth headset and Intercom.

·Wireless networking between PCs in a confined space and where little bandwidth is required.

·Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.

·Transfer of files, contact details, calendar appointments, and reminders between devices with OBEX.

·Replacement of previous wired RS-232 serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.

·For controls where infrared was often used.

·For low bandwidth applications where higher USB bandwidth is not required and cable-free connection desired.

·Sending small advertisements from Bluetooth-enabled advertising hoardings to other, discoverable, Bluetooth devices.

·Wireless bridge between two Industrial Ethernet (e.g., PROFINET) networks.

·Three seventh and eighth generation game consoles, Nintendo's WiFi and Sony's PlayStation 3, PSP Go and PSVita, use Bluetooth for their respective wireless controllers.

·Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a wireless modem.

·Short range transmission of health sensor data from medical devices to mobile phone, set-top box or dedicated telehealth devices.

·Allowing a DECT phone to ring and answer calls on behalf of a nearby mobile phone

·Real-time location systems (RTLS), are used to track and identify the location of objects in real-time using “Nodes” or “tags” attached to, or embedded in the objects tracked, and “Readers” that receive and process the wireless signals from these tags to determine their locations

·Personal security application on mobile phones for prevention of theft or loss of items. The protected item has a Bluetooth marker (e.g. a tag) that is in constant communication with the phone. If the connection is broken (the marker is out of range of the phone) then an alarm is raised. This can also be used as a man overboard alarm. A product using this technology has been available since 2009.

580Q. What are the devices in which Bluetooth works?

Devices

        A Bluetooth USB dongle with a 100 m range. The MacBook Pro, shown, also has a built in Bluetooth adaptor.

        Bluetooth exists in many products, such as the

1.      iPhone,

2.      iPad,

3.      iPod Touch,

4.      Lego Mindstorms NXT,

5.      PlayStation 3,

6.      PSP Go,

7.      telephones,

8.      the Nintendo Wii,

and some high definition

9.      headsets,

10.  modems, and

11.  watches.

581Q. What are the advantages of Wi-Fi?

        Wi-Fi allows cheaper deployment of local area networks (LANs).

        Also spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.

        Manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices.

        Different competitive brands of access points and client network-interfaces can inter-operate at a basic level of service.

        Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance are backwards compatible.

        Unlike mobile phones, any standard Wi-Fi device will work anywhere in the world.

        Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a strong passphrase is used.

        New protocols for quality-of-service (WMM) make Wi-Fi more suitable for latency-sensitive applications (such as voice and video).

        Power saving mechanisms (WMM Power Save) extend battery life.

582Q. What is an inverter? 

An inverter is a power device that transforms DC (Direct Current) into AC (Alternating Current). A typical application would be to convert your available battery or DC power to AC to power sensitive electronic devices that require clean, low distortion sine wave inputs (i.e. microprocessor based instruments and PLC's).

There are two types of "quality" inverters offered, "pure sine wave" and "modified sine wave". A 'pure sine wave' inverter produces a clean, regulated AC output with low distortion. A modified sine wave inverter produces an output that is a rectangular or stepped waveform where both the peak and RMS value is equal to a sine wave of the same magnitude, and is a lower cost alternative to the 'pure sine wave' device. 

583Q. What are Modified Standard Products portfolio called?

Modified Standard Products portfolio includes:  

·      50Hz, 60Hz and 400Hz frequency converters for Military & Aerospace GSE test sets

·      Specialized devices for production test that include remote control and measurement capability

·      Custom frequency converters for military applications (airborne, shipboard and mobile)

·      Custom DC power supplies for military applications (airborne, shipboard and mobile)

·      Custom frequency converters for railroad signaling applications

·      Rugged high voltage AC power sources for oil & gas exploration with RS485 interface and master/slave capability,

·      Custom UPS's for use on US Navy ships, US Army vehicles and USAF test sets.

584Q.   What is called Pulse Width Modulation (PWM) technology?

Switching AC power supplies use Pulse Width Modulation (PWM) technology to synthesize an AC waveform. Filtering at the output of the supply shapes and filters the PWM pulses into a clean sine wave.

Switching technology offers

1.      lighter weight,

2.      smaller size,

3.      cost savings, and

4.      sufficient bandwidth

for most applications.

Switching AC power supplies are ideal for the majority of applications, including:

1.      avionics development and test facilities,

2.      production test of 50Hz, 60Hz & 400Hz products,

3.      circuit development ,

4.      margin testing of frequency & voltage,

5.      operational conformance testing and motor testing,

to name a few.

Different types of avionics and jet engine control systems require testing and simulation over a very wide range of frequencies, 350 to 800Hz.

585Q. Determine polarity by the metallic electrode (E6010)?

1. Clean base metal and position flat
2. Set amperage at 130 to 145 for 5/32" electrode
3. Adjust to either polarity
4. Strike an arc. Hold normal arc length and standard electrode angle and run a bead
5. Listen to the sound of the arc. Correct polarity, with normal arc length and amperage, will produce a regular "crackling" sound. Incorrect polarity, with normal
    length and amperage setting will produce irregular "crackling" and "popping" with an unstable arc
6. See above for characteristics of arc and bead when using metallic electrode on correct and incorrect polarity
7. Adjust to the other polarity and run another bead
8. Clean beads and examine. With the wrong polarity, the electrode negative, you will get many of the bad bead characteristics shown in Lesson 1.6
9. Repeat several times, until you can quickly recognize correct polarity

586Q.  How to  Determine polarity by using the carbon electrode?

1. Clean the base metal and position flat
2. Shape the points of the two carbon electrodes on a grinding wheel, so they are identical with a gradual taper running back 2 or 3 inches from the arc tip
3. Grip one electrode in the electrode holder close to the taper
4. Set amperage at 135 to 150
5. Adjust to either polarity
6. Strike an arc (use shield) and hold for a short time. Change arc length from short to long, affording an observation of the arc action
7. Observe the arc action. If the polarity is negative (straight) the arc will be stable, easy to maintain, uniform, and conical in shape. If the polarity is positive
    (reverse), the arc will be difficult to maintain and will leave a black carbon deposit on the surface of the base metal
8. Change the polarity. Strike an arc with the other electrode and hold for a similar length of time. Observe the arc action as before
9. Examine the ends of the two electrodes and compare. The one used on negative polarity will burn off evenly, keeping its shape. The electrode used on positive polarity will quickly burn off blunt

587Q. Why polarity does change?

        The terms "straight" and "reverse" polarity are used around the shop.

        They may also be expressed as "electrode-negative" and "electrode-positive" polarity. The latter terms are more descriptive and will be used throughout this article.

        Polarity results from the fact that an electrical circuit has a negative and a positive pole. Direct current (DC) flows in one direction, resulting in a constant polarity.

        Alternating current (AC) flows half the time in one direction and half the time in the other, changing its polarity 120 times per second with 60-hertz current.

588Q. what will if irregular polarity is used?

For proper penetration, uniform bead appearance, and good welding results, the correct polarity must be used when welding with any given metallic electrode. Incorrect polarity will cause poor penetration, irregular bead shape, excessive spatter, difficulty in controlling the arc, overheating, and rapid burning of the electrode.

589Q. Negative and positive polarity?

        The first is to use a DC carbon electrode, which will work correctly only on negative polarity.

        The second is to use Fleetweld 5P electrode, which works outstandingly better on positive polarity than on negative polarity.

590Q. What are the problems of the present educated to get employment?

1.      Job oriented but not subject

2.      Cannot solve problems

3.      Don’t know the basics of the law 

4.      Don’t know what is system

5.      No humanity

6.      Don’t know ethics

7.      Produces intellectual materialism

8.      Know only the price but not the value

9.      Logical but not scientific

10.  No commitment

11.  Certificate oriented but not subject oriented

12.  For our own benefit somebody should fight

591Q.

        The use of the AC transformer-type welder necessitated the development of an electrode that would work on either polarity, due to the constant-changing of the polarity in the AC circuit.

        Though AC itself has no polarity, when AC electrodes are used on DC they usually operate best on one specific polarity.

        The covering on the electrode designates which polarity is best and all manufacturers specify on the electrode container what polarity is recommended.

592Q.  Sound travels faster in denser material like solids than the less dense liquids. Wood is a solid and sound travels faster in it than in water, but it can't be more dense than water since it floats in water! What's happening?

A simple backrounder on sound travel goes like this: Sound travels as a message by wiggling atoms and molecules. The closer these are together, the faster the message travels, much like dominoes falling down faster if they are stood up closer together than if they are separated by almost their length. So, if the sound travels along a path where the density of the atoms is higher, then the "message" gets through faster.

We make a subtle error in thinking of wood-the-solid in the way we would think of a piece of metal, or a nice big crystal. Wood is not homogeneous, and it grows as a fiber, not only with structure in a certain direction along the wood, but also with built-in stresses, and complex molecular structures. So, compared to something simple and unstructured like water, a sea of simple H₂O molecules - there isn't much to compare! The microscopic structure of matter has something to do with sound propagation.

Water, a liquid, is not as dense as wood, a solid. Further, along the fiber in wood, the molecules are well stacked, tight and dense. Along the rings, there is a little air (gas) between them, so the sound is not quite as fast in propagating in that direction. Look at the following data on the speed of sound, and notice that sound does travel faster in wood than water, except the 1 piece of data about travel across the rings in Ash - it's the air pockets across the rings that slows the sound message down!

593Q. How does sound travel in different media?

WATER:
Distilled water = 1489 m/sec
Sea Water = 1531 m/sec (higher because it is denser)

WOOD:
Ash, along the fiber = 4670 m/sec
Ash, across the rings = 1390 m/sec, about 3 times slower, and a little slower
than the speed of water!
Beech, along the fiber = 3340 m/sec
Elm, along the fiber = 4120 m/sec
Maple, along the fiber = 4110 m/sec
Oak, along the fiber = 3950 m/sec.

594Q. Why does wood float in water?
        It is pretty clear that the average density of most wood is less than water, floating mainly because of the air pockets between the denser fibrous wood. However, ebony doesn't float. There is a possible lesson in structures of materials found in comparing a piece of ebony with a piece of oak - you really can see and feel the difference.

595Q.  How does sound travel through air and water?

        Sound is motion of atoms, and travels like a message by wiggling the atoms one by one. When you push a line of dominoes over, you send a "message" down the stack, using individual dominoes to carry it - note that the first domino doesn't move to the end of the stack, it just is one of the many carriers of the message, hitting its neighbor, which hits its neighbor, and so on.

        Because sound is this kind of motion of atoms, it really doesn't matter whether the atoms happen to be air atoms (or molecules), or water atoms (or molecules), or wood atoms for that matter!

        So sound starts with something moving or vibrating (like your vocal chords), then this moving thing starts wiggling the atoms in air (gas) or water (liquid) or wood (solid), which then wiggle their neighbors, and so on until the "message" gets to the receiver like our ear.

596Q. How loud does a sound have to be before you go deaf?

Deafness is a complicated medical subject - short loud explosions can make you go deaf, but also long use of what your parents would call "loud music" can also make you go deaf. You can think of deafness as related to the ability to just hear a sound. So do you think you could hear a feather drop on a marching band drum? If your ear bones (ossicles) and nerve endings (in the cochlea) are in good shape, you might just be able to hear this.

A sound which is about 1 million times louder, however would not only be heard by you, but it would be painful and cause damage! These extremes are called the range of hearing. The more you listen to sounds approaching painful ones or even ones that your parents consider too loud, the less likely you are compared to other 3rd graders to hear that feather drop, and the smaller your range of hearing becomes.

You slowly go deaf in the frequency range where people hear. Often you need other people to tell you what "loud" is since your ear can adjust to loud sound levels and make you able to hear loud sounds, but it is still damaging your ear.

597Q.  Compare different loudnesses?

Technically, loudness is measured in physically exact units of sound pressure or sound intensity levels (the unit "decibel" is used, and a tone of 1000 hertz played at a loudness of 40 decibels is at what we would call the pianissimo level (i.e. very soft).

This same tone played at a loudness of 80 decibels is what we would call the fortissimo level (i.e very loud), and it is not twice as loud, but rather 10,000 times louder (decibels are logarithmic, like the earthquake richter scale).

The fact is, our ear is a very incredible sensor, with a hearing range of 1,000,000 - i.e. if that feather dropping on the musical band drum is 1 and we can hear it, that ear can also probably hear something 1,000,000 times louder.

598Q.  How many light years does sound take to go to Pluto?

There is no gas, liquid or solid between here and Pluto! So, guess what? Sound doesn't get there!!!

599Q. How loud do you have to yell for glass to break?

Yelling probably would never break a glass, however a very large chested soprano could sing a note that might break a glass if she got the right pitch. If you take a wine glass and rub the rim with a slightly wetted finger, round and round, you hear a sound which has a high pitch - this is the resonance frequency of the glass.

When you yell, you usually use a lower pitch and a gruff voice. So, practice singing and singing high pitches if you want to break glasses!

600Q.  How fast can sound travel in a telephone cable?

You are probably thinking about your voice travelling in the phone lines, and I will answer that question. You speak into a mouthpiece or microphone which converts sound into something very different - whereas sound is the wiggling of atoms in a gas, liquid or solid, the microphone converts this vibration into electrical energy. Once this is done, the "message" is now electrical, not the mechanical-based sound vibrations, and this electrical message travels at near the speed of light, which is about 1 million times faster than sound vibrations travel. Once the electrical message gets to the end of the cable, it is converted back into sound vibrations by the earpiece in the phone or by the speaker in your computer. Across the United States (about 3000 miles), it takes much less than a second for the electrical message representing your voice to travel.