What is PH?

What is PH?

pH is a measure of hydrogen ion concentration; a measure of the acidity or alkalinityof a solution. The pH scale usually ranges from 0 to 14. Aqueous solutions at 25°C with a pH less than seven are acidic, while those with a pH greater than seven are basic or alkaline. A pH level of is 7.0 at 25°C is defined as 'neutral' because the concentration of H₃O⁺ equals the concentration of OH⁻ in pure water.

Very strong acids may have a negative pH, while very strong bases may have a pH greater than 14.

PH EQUATION

The equation for calculating pH was proposed in 1909 by Danish biochemist Søren Peter Lauritz Sørensen:

pH = -log[H⁺]

where log is the base-10 logarithm and [H⁺] stands for the hydrogen ion concentration in units of moles per liter solution. The term "pH" comes from the German word potenz, which means "power" combined with H, the element symbol for hydrogen, so pH is an abbreviation for "power of hydrogen".

EXAMPLES OF PH VALUES OF COMMON CHEMICALS

We work with many acids (low pH) and bases (high pH) every day. Examples of pH values of lab chemicals and household products include:

0 - hydrochloric acid
2.0 - lemon juice
2.2 - vinegar
4.0 - wine
7.0 - pure water (neutral)
7.4 - human blood
13.0 - lye
14.0 sodium hydroxide

NOT ALL LIQUIDS HAVE A PH VALUE

pH only has meaning in an aqueous solution (in water).

Many chemicals, including liquids, do not have pH values. If there's no water, there's no pH! For example, there is no pH value for vegetable oil, gasoline, or pure alcohol.

IUPAC DEFINITION OF PH

The International Union of Pure and Applied Chemistry (IUPAC) has a slightly different pH scale that is based on electrochemical measurements of a standard buffer solution.

Essentially, the definition using the definition:

pH = -log a_H+

where a_H+ stands for hydrogen activity, which is the effective concentration of hydrogen ions in a solution. This may be slightly different from the true concentration. The IUPAC pH scale also includes thermodynamic factors, which may influence pH.

For most situations, the standard pH definition is sufficient.

HOW PH IS MEASURED

Rough pH measurements may be made using litmus paper or another type of pH paper that is known to change colors around a certain pH value. Most indicators and pH papers are only useful to tell whether a substance is an acid or a base or to identify pH within a narrow range. A universal indicator is a mixture of indicator solutions intended to provide a color change over a pH range of 2 to 10. More accurate measurements are made using primary standards to calibrate a glass electrode and pH meter. The electrode works by measuring the potential difference between a hydrogen electrode and a standard electrode. An example of a standard electrode is silver chloride.

USES OF PH

pH is used in everyday life as well as science and industry. It's used in cooking (e.g., reacting baking powder and an acid to make baked good rise), to design cocktails, in cleaners, and in food preservation.

It's important in pool maintenance and water purification, agriculture, medicine, chemistry, engineering, oceanography, biology, and other sciences.

How Batteries are Used in Everyday Life

How Batteries are Used in Everyday Life

Batteries are one of the most compact and reliable ways to produce energy while on the go. There’s no need to carry around fuel, and their use can often reduce the size of objects that need power while storing energy in one of the most convenient ways invented so far.

To better appreciate batteries in everyday life, let’s take a look at some of the things batteries power.

1. Around the HouseThe most accessible place for batteries to be used is around the house. Disposable batteries tend to power things like remote controls, flashlights, hearing aids, and weight scales. Rechargeable batteries tend to be found powering digital cameras, handheld video game consoles, remote-controlled cars, home-maintenance tools, and more.
   More advanced batteries, such as lithium batteries, are instrumental in providing power to laptops and other devices that draw too much power for a nickel-based battery.
2. Medical EnvironmentsHospitals and emergency services both depend upon batteries for everything from pacemakers to defibrillators They make it possible to hook up electrocardiographic heart monitors that can be moved with the patient to provide an always-on readout of a patient’s vitals.
   In medical environments, nickel-cadmium and lithium-ion batteries tend to be the most popular due to their ability to be recharged.
3. Firefighting and Emergency ResponseOne of the most important tools for any emergency responder is his or her radio. It provides an easy way to communicate in environments where danger may be present. These radios rely solely on large batteries capable of holding an equally large charge.
   Other devices like ECG monitors, flashlights, and even detectors that notify of the presence of harmful substances are all powered by batteries. Each day, these devices are vital in saving the lives of people.
4. Military UseThere are two tools that every person in the armed forces needs as a bare minimum: a utility tool and a set of batteries.
   The importance of batteries in military environments may not seem obvious at first. They’re used to power radio communications, certain types of optical equipment such as night vision apparatuses, and the various tools that make field work safe.
5. Health DevicesArtificial limbs that interact with a person’s nervous system, insulin pumps, valve-assistance devices, and other types of cutting-edge technology designed to improve a person’s life tend to use batteries. Very seldom is there a medical device designed to improve someone’s life or to improve a person’s health that doesn’t use a battery.
6. Construction and LogisticsBatteries are integral when it comes to construction and logistics. Smaller machines such as forklifts may be powered entirely by batteries due to the confined work areas that would make carbon monoxide and other exhaust fumes from combustion engines dangerous.
   They may also be used in larger machines to provide power to electrical systems. Everything from the starter to the radio of such machines may be powered by one or more heavy-duty batteries.

Types of electric cell

Types of Battery Cells

Cylindrical Cell

The cylindrical cell continues to be one of the most widely used packaging styles for primary and secondary batteries. The advantages are ease of manufacture and good mechanical stability. The tubular cylinder can withstand high internal pressures without deforming.

Many lithium and nickel-based cylindrical cells include a positive thermal coefficient (PTC) switch. When exposed to excessive current, the normally conductive polymer heats up and becomes resistive, stopping current flow and acting as short circuit protection. Once the short is removed, the PTC cools down and returns to the conductive state.

Most cylindrical cells also feature a pressure relief mechanism, and the simplest design utilizes a membrane seal that ruptures under high pressure. Leakage and dry-out may occur after the membrane breaks. Re-sealable vents with a spring-loaded valve are the preferred design. Some consumer Li-ion cells include the Charge Interrupt Device (CID) that physically and irreversibly disconnect the cell when activated to an unsafe pressure builds up. Figure 1 shows a cross section of a cylindrical cell.
 

Button Cell

The button cell, also known as coin cell, enabled compact design in portable devices of the 1980s. Higher voltages were achieved by stacking the cells into a tube. Cordless telephones, medical devices and security wands at airports used these batteries.

Although small and inexpensive to build, the stacked button cell fell out of favor and gave way to more conventional battery formats. A drawback of the button cell is swelling if charged too rapidly. Button cells have no safety vent and can only be charged at a 10- to 16-hour charge; however, newer designs claim rapid charge capability.

Most button cells in use today are non-rechargeable and are found in medical implants, watches, hearing aids, car keys and memory backup. Figure 4 illustrates the button cells with a cross section.
 

CAUTION

Keep button cells to out of reach of children. Swallowing a cell can cause serious health problems.

Electrical circuit

Electric Current and its Effects

Electric Components

A simplified conventional pictorial representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram.

Circuit Diagram

A simplified conventional pictorial representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram. A 'circuit diagram' is also known as an electrical diagram, wiring diagram, elementary diagram or electronic schematic.

Electrical Circuit

A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit.
For a bulb to glow, it must be connected to battery rather than a cell, because a bulb will require more power. So if a circuit requires more power, then a battery should be connected.

Cell Holder

A compartment that holds two or more cells together to form a battery is called a cell holder.

Open Circuit

If current does not flow through a circuit, then it is said to be an 'open' circuit or incomplete. Its switch is in 'off' position.

Closed Circuit

A circuit is said to be a closed circuit or complete when current flows through it. Its switch is in 'on' position.

Battery

A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another. To identify the positive and negative terminals, they are denoted as + and -, respectively. These batteries are used in many devices, such as torch lights, mobile phones, calculators and even automobiles.

Symbols

Different symbols are used to represent different components of electrical circuits, but the symbols used must be standardised. These symbols are easy to understand, remember and draw.

Historic launchers of ISRO

Historic launchers of ISRO

Satellite Launch Vehicle-3 (SLV-3) was India's first experimental satellite launch vehicle, which was an all solid, four stage vehicle weighing 17 tonnes with a height of 22m and capable of placing 40 kg class payloads in Low Earth Orbit (LEO).

SLV-3 was successfully launched on July 18, 1980 from Sriharikota Range (SHAR), when Rohini satellite, RS-1, was placed in orbit, thereby making India the sixth member of an exclusive club of space-faring nations . SLV-3 employed an open loop guidance (with stored pitch programme) to steer the vehicle in flight along a pre-determined trajectory. The first experimental flight of SLV-3, in August 1979, was only partially successful. Apart from the July 1980 launch, there were two more launches held in May 1981 and April 1983, orbiting Rohini satellites carrying remote sensing sensors.

The successful culmination of the SLV-3 project showed the way to advanced launch vehicle projects such as the Augmented Satellite Launch Vehicle (ASLV), Polar Satellite Launch Vehicle (PSLV) and the Geosynchronous satellite Launch Vehicle (GSLV).

ASLV

With a lift off weight of 40 tonnes, the 24 m tall ASLV was configured as a five stage, all-solid propellant vehicle, with a mission of orbiting 150 kg class satellites into 400 km circular orbits.

The Augmented Satellite Launch Vehicle (ASLV) Programme was designed to augment the payload capacity to 150 kg, thrice that of SLV-3, for Low Earth Orbits (LEO). While building upon the experience gained from the SLV-3 missions, ASLV proved to be a low cost intermediate vehicle to demonstrate and validate critical technologies, that would be needed for the future launch vehicles like strap-on technology, inertial navigation, bulbous heat shield, vertical integration and closed loop guidance.

Under the ASLV programme four developmental flights were conducted. The first developmental flight took place on March 24, 1987 and the second on July 13, 1988. The third developmental flight, ASLV-D3 was successfully launched on May 20, 1992, when SROSS-C (106 kg) was put into an orbit of 255 x 430 km. ASLV-D4, launched on May 4, 1994, orbited SROSS-C2 weighing 106 kg. It had two payloads, Gamma Ray Burst (GRB) Experiment and Retarding Potentio Analyser (RPA) and functioned for seven years.

Doppler effect

What is the Doppler effect?

When wave energy like sound or radio waves travels from two objects, the wavelength can seem to be changed if one or both of them are moving. This is called the Doppler effect.
The Doppler effect causes the received frequency of a source (how it is perceived when it gets to its destination) to differ from the sent frequency if there is motion that is increasing or decreasing the distance between the source and the receiver. This effect is readily observable as variation in the pitch of sound between a moving source and a stationary observer. Imagine the sound a race car makes as it rushes by, whining high pitched and then suddenly lower.  The high pitched whine is caused by the sound waves being compacted as the car approaches you, the lower pitched  comes after it passes you and is speeding away. The waves are spread out.