Inventions — Set 3

Correct Answer: A. Nikola Tesla

• **Nikola Tesla** = Nikola Tesla invented the AC induction motor in 1887–1888, which uses a rotating magnetic field created by alternating current to turn the rotor without any physical contact between them. • **1888** — Tesla's polyphase AC motor was far more efficient and reliable than DC motors of the era; George Westinghouse licensed the patents and used them to build the modern AC power grid. • 💡 Wrong-option analysis: Andre-Marie Ampere: developed the mathematical theory of electromagnetism and discovered that parallel wires carrying current attract each other; Thomas Edison: championed direct current (DC) motors and power systems; George Ohm: formulated Ohm's Law relating voltage, current, and resistance.

Correct Answer: A. Joseph Bramah

• **Joseph Bramah** = Joseph Bramah invented the hydraulic press in 1795, applying Pascal's principle that pressure applied to an enclosed fluid is transmitted equally in all directions to create a machine capable of exerting enormous force. • **1795** — A small input force on a narrow piston produces a large output force on a wide piston; this principle is now fundamental to hydraulic jacks, car lifts, and industrial presses. • 💡 Wrong-option analysis: Blaise Pascal: formulated Pascal's Principle on fluid pressure (the theoretical basis) but did not build the hydraulic press; Daniel Bernoulli: derived Bernoulli's principle about fluid flow and pressure; Archimedes: discovered the principle of buoyancy and the lever but lived in ancient Greece.

Correct Answer: D. Christopher Sholes

• **Christopher Sholes** = Christopher Sholes invented the first commercially successful typewriter in the late 1860s and designed the QWERTY keyboard layout to reduce mechanical key jamming by separating commonly used letter pairs. • **1868** — Sholes obtained a patent in 1868; the Remington company manufactured and marketed the machine from 1873, making it the world's first mass-produced typewriter. • 💡 Wrong-option analysis: Mark Twain: was reportedly the first author to submit a typewritten manuscript (Life on the Mississippi) but did not invent the machine; Samuel Morse: invented the electric telegraph and Morse code; Johannes Gutenberg: invented the movable-type printing press around 1440.

Correct Answer: D. Percy Spencer

• **Percy Spencer** = Percy Spencer accidentally discovered microwave cooking in 1945 when a chocolate bar in his pocket melted while he was testing a radar magnetron; he quickly developed the first microwave oven. • **1945** — The first commercial microwave, marketed as the 'Radarange' in 1947, stood 1.8 m tall and weighed 340 kg; countertop home models became affordable only in the 1970s. • 💡 Wrong-option analysis: Richard Feynman: Nobel Prize-winning theoretical physicist known for quantum electrodynamics, not kitchen appliances; Robert Millikan: measured the electron's charge; Linus Pauling: Nobel laureate in chemistry known for chemical bonding theory.

Correct Answer: C. Joseph von Fraunhofer

• **Joseph von Fraunhofer** = Joseph von Fraunhofer invented the spectroscope around 1814 and used it to observe and catalogue hundreds of dark absorption lines in the solar spectrum (now called Fraunhofer lines), enabling chemical analysis of distant stars. • **1814** — Fraunhofer mapped 574 spectral lines; later work by Kirchhoff and Bunsen showed these lines correspond to specific chemical elements, founding astronomical spectroscopy. • 💡 Wrong-option analysis: Max Planck: originated quantum theory and the concept of energy quanta; Isaac Newton: used a prism to split white light into a spectrum but did not build a spectroscope; Gustav Kirchhoff: formulated the laws of spectroscopy and identified chemical elements by their spectral lines, but Fraunhofer built the instrument first.

Correct Answer: A. Walter Hunt

• **Walter Hunt** = Walter Hunt invented the modern safety pin in 1849, designing it with a coiled spring and a guard clasp so the sharp point is always covered, preventing accidental injury. • **1849** — Hunt designed the safety pin in about three hours to repay a $15 debt and then sold the patent for $400; the design has remained virtually unchanged for over 170 years. • 💡 Wrong-option analysis: Levi Strauss: invented copper-riveted blue jeans (denim trousers) in 1873; Elias Howe: patented the lockstitch sewing machine in 1846; Isaac Singer: improved and commercialised the sewing machine.

Correct Answer: B. Nikolaus Otto

• **Nikolaus Otto** = Nikolaus Otto developed the first practical four-stroke internal combustion engine in 1876, establishing the intake–compression–power–exhaust cycle still used in virtually all petrol engines today. • **1876** — Otto's four-stroke cycle (also called the Otto cycle) achieved about 14% thermal efficiency, far better than earlier two-stroke engines; over 2 million Otto engines were built by 1900. • 💡 Wrong-option analysis: Henry Ford: perfected the moving assembly line for mass-producing cars but did not invent the engine; Gottlieb Daimler: used and refined Otto's engine to build the first motorcycle (1885) and automobile; Karl Benz: designed the first petrol-powered automobile (1885) but used an engine developed from Otto's design.

Correct Answer: A. George Eastman

• **George Eastman** = George Eastman invented flexible roll film in 1884 and founded the Kodak company; his 1888 Kodak camera loaded with roll film made photography accessible to ordinary people for the first time. • **1884** — Before Eastman's roll film, photographers used heavy fragile glass plates; roll film could capture many exposures in sequence and be wound forward automatically. • 💡 Wrong-option analysis: Edwin Land: invented the instant (Polaroid) camera in 1947; William Fox Talbot: invented the calotype process (paper negatives) around 1841; Louis Daguerre: invented the daguerreotype process (silver-plate images) in 1839.

Correct Answer: A. Robert Bunsen

• **Robert Bunsen** = Robert Bunsen, together with his laboratory technician Peter Desaga, designed the Bunsen burner in 1857 to produce a hot, clean, controllable flame for laboratory heating by premixing gas and air before combustion. • **1857** — The Bunsen burner reaches temperatures of about 1,500°C; by mixing gas with oxygen before ignition, it produces a nearly invisible blue flame with no soot, ideal for chemical experiments. • 💡 Wrong-option analysis: Antoine Lavoisier: established modern chemistry and identified oxygen's role in combustion but lived in the 18th century; John Dalton: proposed the atomic theory of matter; Michael Faraday: discovered electromagnetic induction and laws of electrolysis.

Correct Answer: A. Willem Einthoven

• **Willem Einthoven** = Willem Einthoven developed the first practical electrocardiogram in 1903 using a string galvanometer sensitive enough to detect the tiny electrical signals produced by the heart with each beat. • **1903** — Einthoven assigned the letters P, Q, R, S, and T to the waves on the ECG trace; he received the Nobel Prize in Physiology or Medicine in 1924 for this invention. • 💡 Wrong-option analysis: Alexander Fleming: discovered penicillin in 1928; Edward Jenner: developed the smallpox vaccine in 1796; Louis Pasteur: developed germ theory and invented pasteurisation and early vaccines.