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Measure for Measure Trivia Quiz
Scientific research needs many quantities to be measured. And to get coherent results, the measurements must be standardized. The SI units fulfil this need of standardization. Match the specific SI unit to the quantity measured.
Pressure is defined as the force exerted perpendicularly on an area.
The SI unit of pressure is the pascal (abbreviation: Pa), whereby one pascal equals one kilogram divided by one metre and one second squared. In a formula: 1 Pa =1 kg * 1 m(-1) * 1 s(-2). The numbers between brackets are exponents, so the number -1 indicates division and -2 indicates division by the square.
The pascal was named after Blaise Pascal (1623-1662), a French mathematician and physicist. He worked on hydraulic pressure. When he heard about Torricelli's experiment involving the mercury barometer, Pascal took the next step by trying out the same contraption at various altitudes, thus demonstrating that the air exerts pressure.
2. SI unit for electric charge
Answer: Coulomb
Electric charge is the property of matter experiencing force in a magnetic field. On the atomic level, electric charge is the property of having more electrons than protons (negative charge) or more protons than electrons (positive charge). On the atomic and subatomic level, quantum effects take place, but in the macroscopic objects these are not observable.
The SI unit for electrical charge is the coulomb (abbreviated C), where one coulomb equals one ampere transported in one second. The formula is thus 1 C = 1 A * 1 s. This unit was named after Charles-Augustin de Coulomb (1736-1806), a French military engineer and physicist who made extensive studies of electricity and magnetism.
3. SI unit of electrical resistance
Answer: Ohm
Electrical resistance is the measure for the difficulty of an electric current to pass a certain object (acting as the conductor). The material of
the conductor is one of the determining factors in the equation: silver and copper are good conductors with low resistance, while rubber and Teflon have very high resistance.
The shape and length of the conductor also plays a role: a long thin copper wire has more resistance than a thick short stubby copper thread.
The SI unit for electrical resistance is the ohm, where 1 ohm equals 1 volt divided by 1 ampere. Or if we go by the seven basic units of the SI: 1 ohm = 1 kg*1 m(2)*1 s(-3)*1 A(-2). The symbol for the ohm is the Greek capital omega, which can't be correctly displayed here.
The inverse of the ohm is the siemens: a measure for electrical conductivity. The siemens is abbreviated as a capital S.
The ohm was named after Georg Simon Ohm (1789-1854), a German physicist and mathematician. He mostly studied electricity, and published a minor work on acoustics. The siemens was named after the German inventor Werner von Siemens (1816-1892), founder of the eponymous company.
4. SI unit of magnetic flux
Answer: Weber
Magnetic flux is defined as the amount of magnetism passing through an open surface. (If the surface is closed, the magnetic flux is exactly zero).
The SI unit for magnetic flux is the Weber, defined as one volt multiplied by one second. Or in the basic SI units: 1 Wb = 1 kg * 1 m2 * 1 s(-2) * 1 A(-1).
The weber was named after the German physicist Wilhelm Eduard Weber (1804-1891), inventor (together with Carl Friedrich Gauss) of the electromagnetic telegraph.
5. SI unit of inductance
Answer: Henry
Inductance is a measure for the property of an electrical conductor by which a change in the current invokes an electromotive force in the conductor itself as well as in nearby conductors.
The American scientist Joseph Henry (1797-1878) studied electromagnetism intensively, and discovered the phenomenon of self-inductance. He gave his name to the SI unit of inductance, the henry.
One henry (abbreviated H) equals one weber per ampere, or (in the basic SI units) 1 H = 1 kg* 1 m2 * 1 s(-2) * 1 A (-2).
6. SI unit of illuminance
Answer: Lux
Illuminance is the total luminous flux per area, so the perceived power of light falling on a surface.
The SI unit for illuminance is the lux, derived from the Latin word for light, defined as 1 lumen per square metre. The lux is abbreviated lx, and the lumen is abbreviated lm. So 1 lx= 1 lm/m2.
7. SI unit of frequency
Answer: Hertz
Frequency is the number of occurrences of a repeating unit per time unit. One can use the word frequency on a day-to-day basis, such as the frequency of publication of a magazine.
In a scientific context, the frequency is measured as the number of occurrences per second. The SI unit is the hertz (abbreviated Hz), and the formula is quite simple: 1 Hz = 1 s(-1).
The hertz was named after the German scientist Heinrich Hertz (1857-1894). During his studies of electromagnetism, Hertz succeeded in creating electromagnetic waves with the frequency typical of FM radio waves (between 87 and 108 MHz).
In radioactivity, there is a similar unit, the becquerel, for the number of decays per second.
8. SI unit of energy
Answer: Joule
Energy is defined as the force exerted on an object to heat it or to move it. The SI unit of energy is the joule (abbreviated J), defined as one newton multiplied by one metre. Or to put it In the basic SI units: 1 J= 1 kg* 1 m2 * 1 s(-2).
The English physicist James Prescott Joule (1818-1889) performed several experiments demonstrating the mechanical equivalent of heat: the amount of energy needed to increase the temperature of water.
The calorie was a more ancient unit of energy, but is now, from a scientific point of view, obsolete. The calorie was defined as the amount of energy necessary to heat a gram of water with one degree Celsius, but this varied with the starting temperature of the water. The joule is no longer dependent on external circumstances and is thus scientifically much more valuable.
9. SI unit of capacitance
Answer: Farad
Capacitance is defined as the ability to store an electrical charge. The SI unit for capacitance is the farad (abbreviated F) and it equals one coulomb per volt. In basic SI units we get the equation 1 F = 1 s4 * 1 A2 * 1 kg(-1) * 1 m(-2).
The farad was named after Michael Faraday (1791-1867), the English scientist fascinated by electromagnetism and electrochemistry. Faraday demonstrated electromagnetic induction. He also proved that anyone in a conductor is safe: the principle of the Faraday cage. For instance, if you're in a car while lightning strikes, you're perfectly safe inside the car but you may not survive the lightning outside your car.
10. SI unit for an absorbed dose of ionizing radiation
Answer: Gray
Ionizing radiation is the type of radiation with so much energy that it can knock free electrons from molecules or atoms, thus turning the atoms or molecules into ions. Ionizing radiation consists either of subatomic particles travelling at high speed (usually exceeding 3km per second) or highly energized electromagnetic waves.
Ionizing radiation can be beneficial for the body (radiation therapy of some cancers) but can also be potentially harmful, depending on the dose. That's why the absorbed dose has a specific SI unit: the gray (abbreviated Gy) and named after the British scientist Louis Harold Gray (1905-1965), one of the pioneers in radiobiology.
One gray equals one joule per kilogram, or in basic units: 1 Gy = 1 m2 * 1 s(-2).
The gray does not take in account any medical consequences. There is a SI unit derived from the gray that does take into account (average) medical consequences: the Sievert, calculated by expanding the equation with a factor for the type of radiation. For instance, alpha particles (helium nuclei- are twenty times as dangerous as X-rays.
This quiz was reviewed by FunTrivia editor rossian before going online.
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