Physics Basics — Set 5

Correct Answer: D. Ohm

• **Ohm** = The Ohm (Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. • **R = V/I** — By Ohm's Law, resistance equals voltage divided by current; one Ohm = one Volt per Ampere. • 💡 Wrong-option analysis: Ampere: is the SI unit of electric current; Volt: is the SI unit of electric potential difference; Farad: is the SI unit of electrical capacitance.

Correct Answer: A. Michael Faraday

• **Michael Faraday** = Michael Faraday published the two laws of electrolysis in 1834, relating the amount of substance deposited to the amount of electric charge passed. • **1834** — Faraday's First Law: mass deposited is proportional to charge; Second Law: mass deposited is proportional to equivalent weight. • 💡 Wrong-option analysis: Joseph Priestley: discovered oxygen; John Dalton: proposed the atomic theory; Dmitri Mendeleev: created the Periodic Table of Elements.

Correct Answer: C. Hygrometer

• **Hygrometer** = A hygrometer is an instrument used to measure the amount of water vapor (humidity) in the atmosphere. • **relative humidity** — Hygrometers measure relative humidity (%), essential for weather forecasting and industrial processes. • 💡 Wrong-option analysis: Altimeter: measures altitude of an aircraft above sea level; Hydrometer: measures the specific gravity (density) of liquids, not atmospheric humidity; Barometer: measures atmospheric pressure, not humidity.

Correct Answer: C. Archimedes' Principle

• **Archimedes' Principle** = Archimedes' Principle states that the upward buoyant force on an immersed object equals the weight of the fluid it displaces. • **buoyant force = weight of fluid displaced** — This is why ships float: they displace water equal in weight to the ship's own weight. • 💡 Wrong-option analysis: Ohm's Law: relates voltage, current, and resistance in electrical circuits; Pascal's Law: states that pressure in an enclosed fluid is transmitted equally in all directions; Newton's Law: refers to laws of motion and gravitation, not fluid buoyancy.

Correct Answer: C. Newton

• **Newton** = The Newton is the SI unit of force, named in honor of Isaac Newton. • **1 N = 1 kg·m/s²** — One Newton is the force needed to accelerate a mass of one kilogram at one meter per second squared. • 💡 Wrong-option analysis: Pascal: is the SI unit of pressure (force per area); Joule: is the SI unit of work and energy; Watt: is the SI unit of power.

Correct Answer: A. Alessandro Volta

• **Alessandro Volta** = Alessandro Volta invented the first chemical battery, the Voltaic Pile, in 1800 using alternating zinc and copper discs. • **1800** — The Voltaic Pile was the first device to produce a continuous, steady electric current from a chemical reaction. • 💡 Wrong-option analysis: Benjamin Franklin: proved lightning is electrical and invented the lightning rod, not the battery; Thomas Edison: improved electrical systems and invented the phonograph and light bulb; Luigi Galvani: discovered bioelectricity in frogs but did not invent the battery.

Correct Answer: A. Altimeter

• **Altimeter** = An altimeter is an instrument used to measure the altitude of an object above a fixed level, usually sea level. • **atmospheric pressure** — Most aircraft altimeters work by measuring atmospheric pressure, which decreases with altitude. • 💡 Wrong-option analysis: Lactometer: measures the purity of milk by density; Anemometer: measures wind speed; Fathometer: measures water depth using sound waves.

Correct Answer: A. Weber

• **Weber** = The Weber (Wb) is the SI unit of magnetic flux, named after German physicist Wilhelm Eduard Weber. • **1 Wb = 1 V·s** — One Weber is the amount of flux that, when reduced to zero uniformly in one second, induces one volt in a single-turn loop. • 💡 Wrong-option analysis: Henry: is the SI unit of electrical inductance; Farad: is the SI unit of electrical capacitance; Tesla: is the SI unit of magnetic flux density (Weber per square meter).

Correct Answer: B. Voltmeter

• **Voltmeter** = A voltmeter is an instrument used for measuring the electric potential difference (voltage) between two points in a circuit. • **parallel connection** — A voltmeter is always connected in parallel with the component whose voltage is being measured. • 💡 Wrong-option analysis: Galvanometer: detects and measures very small currents, not voltage; Rheostat: is a variable resistor used to control current, not measure voltage; Ammeter: measures electric current and is connected in series, not parallel.

Correct Answer: D. James Chadwick

• **James Chadwick** = James Chadwick discovered the neutron in 1932, a neutral subatomic particle found in the atomic nucleus alongside protons. • **1932** — Chadwick bombarded beryllium with alpha particles and identified the neutral radiation as neutrons. • 💡 Wrong-option analysis: Niels Bohr: proposed the Bohr model of the atom with quantized electron orbits; Ernest Rutherford: discovered the proton and the atomic nucleus, but not the neutron; Enrico Fermi: built the first nuclear reactor and pioneered nuclear fission research.