Numerical Constants
Answers to RF Cafe Quiz #15

Return to RF Cafe Quiz #15

1. To which constant is 6.022*10²³/ mol assigned?

b) Avogadro's constant

Avogadro's number is the number of entities of a substance to make a mole. Avogadro's number is formally defined to be the number of carbon-12 atoms in 12 grams of unbound carbon-12 in its rest-energy electronic state. So, there are 6.022*10²³ carbon-12 atoms in a gram of carbon-12.

2. To which constant is 2.718 assigned?

a) base of natural logarithms

e¹ = 2.718281828...

The definition is based on the fact that the area of the region under the curve of a hyperbola (y=1/x) to the x-axis, between 1 and e, equals 1. That gives the relationship in calculus where

       ln(e)=∫1/x*dx, between x=1 and x=e

3. To which constant is 9,192,631,770 assigned?

b) oscillations of a cesium-133 atom in exactly one second

The cesium atom's natural frequency was formally recognized as the new international unit of time in 1967: the second was defined as exactly 9,192,631,770 oscillations or cycles of the cesium atom's resonant frequency.

4. To which constant is 1.616*10^-35 m assigned?

a) Planck length

The Planck length is often defined as the shortest possible length, but what it really means if the shortest possible measurable length. This is because quantum effects significantly distort the measurement of distances smaller than the Planck length.

5. To which constant is 9.11*10^-28 g assigned?

c) electron rest mass

I'll let Jorge, of the Journal of Theoretics explain it.

6. To which constant is 9.81 m/s² assigned?

c) acceleration of gravity near Earth's surface

To be more exact, it is the acceleration of gravity at the latitude of the Royal Observatory in the U.K.. Due to centrifugal force created by the Earth's rotation about its axis, the measured force is greater near the poles than near the equator.

7. To which constant is 8.854*10^-12 F/m assigned?

c) permittivity of free space

This is often written as ε₀. The permittivity of free space (ε₀) is related to the speed of light and the permeability of free space (μ₀) by the following familiar equation  1/c = √(ε_0*μ₀)

8. To which constant is 2.998*10⁸ m/s assigned to?

d) speed of light in a vacuum

The speed of light in vacuum is defined to be exactly 299,792,458 meters per second.

9. To which constant is 1.3807*10^-23 J/K assigned?

a) Boltzmann's constant

The Boltzmann constant (k) relates energy and temperature at the particle level. Numerically, it is equal to the gas constant (R) divided by the Avogadro constant (N_a), and it appears in equations like for noise in a given bandwidth (kTB).

10. To which constant is 1.257*10^-6 H/m assigned?

d) permeability of free space

This is often written as μ₀. The permeability of free space (μ₀) is related to the speed of light and the permittivity of free space (ε₀) by the following familiar equation  1/c = √(ε_0*μ₀)