QUES: Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC in Judea and by the 7th century BC in Ancient Greece. Zinc metal was not produced on a large scale until the 12th century in India and was unknown to Europe until the end of the 16th century. The mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC. To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc. Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow".
Brass is an alloy of what two elements?

ANS: copper and zinc

QUES: The Shang dynasty oracle bone script and the Zhou dynasty scripts found on Chinese bronze inscriptions are no longer used; the oldest script that is still in use today is the Seal Script ((), zhuanshu). It evolved organically out of the Spring and Autumn period Zhou script, and was adopted in a standardized form under the first Emperor of China, Qin Shi Huang. The seal script, as the name suggests, is now used only in artistic seals. Few people are still able to read it effortlessly today, although the art of carving a traditional seal in the script remains alive; some calligraphers also work in this style.
What script is the oldest and still in use today?

ANS: Seal

QUES: Plants and various other groups of photosynthetic eukaryotes collectively known as "algae" have unique organelles known as chloroplasts. Chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. Chloroplasts and cyanobacteria contain the blue-green pigment chlorophyll a. Chlorophyll a (as well as its plant and green algal-specific cousin chlorophyll b)[a] absorbs light in the blue-violet and orange/red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. The energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy-rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen (O2) as a by-product.
From what ancient oxygen producing plant are chloroplasts descended?

ANS: cyanobacteria

QUES: Holes through a PCB are typically drilled with small-diameter drill bits made of solid coated tungsten carbide. Coated tungsten carbide is recommended since many board materials are very abrasive and drilling must be high RPM and high feed to be cost effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling with high-speed-steel is simply not feasible since the drill bits will dull quickly and thus tear the copper and ruin the boards. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole.
What kind of material sometimes used for drilling will lose sharpness quickly if used for PCBs?

ANS:
high-speed-steel