General Science

Electric engines have the highest efficiency among all engine types because they convert electrical energy directly to mechanical energy with minimal losses. Petrol and diesel engines have significant thermal losses, while steam engines are the least efficient due to multiple energy conversions.

A standard dry cell (zinc-carbon battery) uses a paste of ammonium chloride as the electrolyte, which allows ion flow between the zinc anode and carbon cathode. Manganese dioxide is the cathode depolarizer, not the electrolyte.

Nickel-Cadmium (NiCd) batteries are rechargeable and were commonly used in portable devices like torches and electric shavers due to their ability to handle repeated charge-discharge cycles. Nickel-cadmium forms the electrode pair in these batteries.

A Bunsen burner operates on Bernoulli's principle - the high-velocity gas flow creates a pressure drop that draws in air through the air vents, mixing with the gas before combustion. Gas lighters use piezoelectric effect, and gas stoves don't rely primarily on Bernoulli's principle.

Cryogenic engines use extremely cold liquefied gases like liquid hydrogen and liquid oxygen as fuel, making them essential for rocket technology where maximum thrust and efficiency are required. They're not used in refrigerators or submarines.

A greenhouse is a structure made primarily of glass that allows sunlight in while trapping heat to maintain temperature within a desired range for plant cultivation. The glass acts as a selective transmitter of solar radiation.

A dialyzer is a medical device that performs the function of kidneys in patients with renal failure by removing waste products and excess fluids from blood through dialysis. It's not related to sound control, battery charging, or timekeeping.

In a pressure cooker, high pressure actually INCREASES the boiling point of water (not decreases it), allowing food to cook at higher temperatures. This is why food cooks faster. The steam and pressure do help cook food earlier, and fuel is saved due to faster cooking.

Nichrome (an alloy of nickel and chromium) is used for heating elements because it has high resistance, high melting point, and doesn't oxidize easily at high temperatures. Pure nickel, chromium, or tungsten don't have the right combination of properties for heating elements.

An atomic pile (early nuclear reactor) produces radioactive substances through controlled nuclear reactions. The pile sustains a chain reaction that creates radioactive isotopes through neutron bombardment of stable nuclei. Wilson cloud chambers detect radiation tracks, electronic guns emit electrons in vacuum tubes, and transistors are semiconductor devices - none produce radioactivity.

A floppy disc is a magnetic storage medium used to store and retrieve digital data. Unlike compilers (which translate code) or core memory (primary system memory), a floppy disc is specifically designed as an external storage device. Software refers to programs, not hardware storage media.

Sodium bicarbonate (NaHCO3) reacts rapidly with dilute sulfuric acid to produce carbon dioxide gas through acid-base reaction: 2NaHCO3 + H2SO4 → Na2SO4 + 2H2O + 2CO2. This quick CO2 generation makes it ideal for fire extinguishers. Marble, magnesite, and limestone react too slowly for effective emergency use.

A safety fuse needs high resistance to heat up and melt at a specific low temperature when excess current flows. High resistance converts electrical energy to heat efficiently, while low melting point ensures quick breakage. High melting point would delay circuit protection, and low resistance would prevent adequate heating.

Ultra-high-molecular-weight polyethylene (UHMWPE) is used in bulletproof vests and armor due to its exceptional strength-to-weight ratio and impact resistance. It absorbs and disperses kinetic energy from projectiles. Polyamides (nylon) are strong but less impact-resistant, PVC is rigid, polycarbonates are impact-resistant but not used for ballistic protection.

Cellular (internal) respiration refers to gas exchange between blood and tissue fluid, where oxygen diffuses from blood into tissues and carbon dioxide moves from tissues into blood. External respiration is lung alveoli-capillary exchange. Tissue respiration is cellular metabolic processes. Option C accurately describes blood-tissue fluid gas exchange.

Karl Landsteiner discovered the ABO blood group system in 1901, for which he received the Nobel Prize. Harvey discovered blood circulation, Ringer developed Ringer's solution, and Pasteur contributed to germ theory. Landsteiner's work on blood antigen-antibody reactions revolutionized transfusion medicine.

Cold-blooded (ectothermic) animals like frogs cannot regulate their body temperature internally. Their temperature changes with the environment, and they rely on external heat sources. Options A, B, and D are incorrect - their blood isn't always cold, they inhabit various temperatures, and their blood temperature matches the environment.

Type O blood lacks both A and B antigens on red blood cells, making it compatible with all other blood types. Universal donors can give to anyone because recipient antibodies won't attack O cells. Type O has both anti-A and anti-B antibodies in plasma, but the absent RBC antigens are what matters for donation.

Calcium ions (Ca2+) are essential cofactors in the blood coagulation cascade. They participate in multiple steps including activation of clotting factors and conversion of prothrombin to thrombin. Without calcium, the clotting process cannot proceed effectively. Sodium and potassium are involved in nerve conduction, and chloride is an electrolyte.

Transistors are fundamental components in hearing aids due to their small size and ability to amplify weak electrical signals from microphones. While transistors exist in many electronic devices, hearing aids particularly rely on them for signal processing. Wrist watches may use them, fuses use melting conductors, and fluorescent lamps use gas discharge tubes.

Blood type AB lacks both anti-A and anti-B antibodies in plasma, allowing it to receive blood from any group (A, B, AB, or O) without antibody-mediated rejection. Universal acceptors can receive from all donors because their immune system won't attack any blood type antigens. Option A and C are false descriptions, and D merely restates the blood type.

Monocytes are the largest white blood cells (leukocytes) in vertebrate blood. They are highly phagocytic and can migrate out of blood vessels into tissues to become macrophages, where they engulf pathogens and cellular debris. Thrombocytes (platelets) are cell fragments involved in clotting, erythrocytes (RBCs) carry oxygen, and amoebocytes are invertebrate defense cells.

 The technique used to transmit audio signals in television broadcast is pulse code modulation.