Outbreeding refers to matings between individuals from different populations, subspecies, or species whereas hybridization is the process of crossing two genetically different individuals to result in a third individual with a different, often preferred, set of traits. Plants of the same species cross easily and produce fertile progeny. Such plants are referred to as cross-pollinated plants.

Inbreeding refers to mating of related individuals. It results in a decline in survival and reproduction (reproductive fitness), known as inbreeding depression, in most species of plants and animals. Outbreeding refers to matings between individuals from different populations, subspecies, or species. Plant hybridization is the process of crossbreeding between genetically dissimilar parents to produce a hybrid. It frequently results in polyploid offspring. In biology, outbreeding depression is when crosses between two genetically distant groups or populations results in a reduction of fitness. The concept is in contrast to inbreeding depression, although the two effects can occur simultaneously.

The Harappa site was first briefly excavated by Sir Alexander Cunningham in 1872-73, two decades after brick robbers carried off the visible remains of the city. He found an Indus seal of unknown origin.
The first extensive excavations at Harappa were started by Rai Bahadur Daya Ram Sahni in 1920. His work and contemporaneous excavations at Mohenjo-daro first brought to the world's attention the existence of the forgotten Indus Valley civilization as the earliest urban culture in the Indian subcontinent.
His work was followed later in the decade by that of Madho Sarup Vats, also of the Archaeological Survery of India. M.S. Vats first excavated the "Granary," and published the results of his and Sahni's excavations in 1940. Excavations by other archaeologists continued in the 1930's, and in 1946 Sir Mortimer Wheeler excavated the so-called fortification walls and found the first pre-Indus Valley civilization (Kot Dijian) deposits.

After independence, Harappa was excavated by Mohammed Rafique Mughal of the Archaeological Survey of Pakistan in 1966. In 1986, the first systematic, multi-disciplinary excavations of an Indus Valley city were begun by the Harappa Archaeological Project (HARP), under the direction of George F. Dales and J. Mark Kenoyer. These excavations, now also co-directed by Richard H. Meadow, have continued almost every year since then.

There is an enormous amount still to be learned about the site, most of which remains unexcavated. The earliest deposits on the site go back to 3300 B.C. and the area seems to have been continuosly inhabited ever since. Archaeologists think that ancient Harappa was the urban center dominating the upper Indus region, much like Mohenjo-daro dominated the lower Indus Valley and Ganweriwala might have been the urban center for what is now Rajasthan

Over the past century, archaeologists working in the Middle East have time and again excavated seals bearing what they call “Indus-style inscriptions”, complete with the script and the usual unicorn or bull. However, such Indus- or Harappan-style seals discovered “overseas”, so to speak, displayed a different shape as well as craftsmanship, being shaped either as circles or cylinders which were “rolled over wet clay rather than pressed upon it.” At times, such seals have also been discovered from within the defined boundaries of the Indus Valley Civilization – or, shall we say, Meluhha, as most modern scholars agree the contemporarily-named Indus Valley Civilization was called at the time of its existence – such as the “Gulf seal” discovered from Lothal, Gujarat. All of these discoveries give rise to many questions: did the people from the-then Dilmun and Magan Civilizations – as the civilizations from the modern-day Bahrain and Oman were respectively known – produce those seals indigenously? If so, did they understand the Meluhhan language? Or did the Meluhhans themselves make different seals for trade-items being sent to different places? In which case, too, the question remains: could the people from neighbouring civilizations understand the script? If they could not, then why did the Meluhhans send them these seals? Or, if those civilizations produced them indigenously, why so? Answers to these questions might hold the key to the decipherment of the Indus Script, by aiding archaeologists in the discovery of a bilingual text: the Rosetta Stone of the Indus Valley Civilization.

Kirchhoff’s Second law: Loop law

• Loop law is also known as Kirchhoff’s Second Law.
• It states that in a closed loop,algebraic sum of Emfsis equal to the algebraic sum of product of resistances and respective currents flowing through them.
• Consider a simple circuit havingEmfs = E₁ and E₂; R₁ and R₂ =resistances; current =I₁ and I₂.
• Then according to this law : E₁+E₂=I₁R₁+ I₂R₂
• For example:-
  • Consider given figure,let Emfs be E₁ and E₂ internal resistances be R₁, R₂ and R₃.
  • Steps to use Kirchhoff’s law:-
    • Choose the loop to apply Kirchhoff’s law.
    • Assume any direction.
    • Emf is +ive if assumed direction leaving +ive terminal of battery.
    • IR is +ive if the current in the assumed direction.