B: a complex character

  • Posted on: 19 April 2014
  • By: admin

The symbol B we find him in 3 forms:

  • Bel
  • byte
  • magnetic flux density B

What does it mean and where to apply each of the three?

We would start from the last, the magnetic flux density B. It is a symbol that denotes a magnitude and not a unit of measure, for which it is not confusable.

We can find phrases like this  "the magnetic flux density B is equal to 5 T" where T indicates the unit of measurement derived Tesla.

Example: " The authors suggest that the sinoatrial node of the heart, controlling the heart rate, may be the most sensitive region to the current and calculate that, for a field of 5 T, the current density in this region is approximately 100 mA / m² " source http://www.icnirp.de/documents/statgdlita.pdf As you can see the only real unit is the tesla T of [ V · s · m-2] = [ kg · s-2 · A-1]

The more complicated the situation for Bel and Byte.

Here both variables are units of measurement. We must say that the "abusive" one is the Bel, but it has a very specific kind of use that will be difficult to unseat.

 

Bel

B may be the expression of the Bel (which is exencially a relationship between variables) and that "lives" in decibels.

From Wikipedia, we quote: 

"The Bel, the symbol B, is a unit of relative measurement, with which a physical quantity (such as the power of a radiation or signal ) is compared to a reference value on a logarithmic scale"

So I say this by saying nice size log ( something / reference ) namely base-10 logarithm of ( something [ any unit ] / reference of anything [ any unit ] )

The decibel (symbol dB) is one tenth of a bel ( symbol B): 10 dB 1 = B. The bel has now fallen into disuse, but is still the basic unit of measure by which the decibel is derived, also the corresponding measures are numbers pure and precisely are obtained as the logarithm of the ratio of two homogeneous ( ie expressed in the same units and such, then , that their relationship is a dimensionless pure number ) . When we speak of acoustic automatic fire is thought to decibels ( taking advantage of the logarithmic scale given by Bel because they have a great range of variability ) . In particular, then , are the dB ' A-weighted , "meaning transformati for adattardi c ome funzinoa the human ear .

 

Byte

Here siamo invec nell'imformatica . Again from Wikipedia initaliano " the symbol used for the byte as the unit of measurement for the amount of information is B (identical to the symbol of the beautiful ) ; the uppercase letter is reserved only for units of measurement taken from the surnames of the founders, but the International Electrotechnical Commission (IEC) has decided to make an exception since b is generally used to indicate the bit (the standard symbol for would -bit extended ) . " For this reason , there being LIEC behind the B intended as a byte , let's say that the abusibo is the decibel ... We take the opportunity for a generalization : if a file is composed of 1,000 kB , we are tempted to say, that corresponds to a 1 MB. We use the but it would be more correct to use " prefixes for binary multiples " . In fact it is 1 mega size 1000 kB, but in 1024 kB . Let's see if you can resolve this uncertainty. 1 MB = 1 million bytes (1000 ^ 2, 10 ^ 6 ) The use of this definition is recommended by IEC . It is very often used when talking about networking and storage devices such as hard drives and DVD . 1 MiB = 1 048 576 bytes, (1024 ^ 2, 2 ^ 20) this value (which corresponds to a mebibyte ) is associated with the megabytes especially when it comes to file size and memory addressing , this is because the addresses are expressed in powers of 2 and the memory is made ​​easier with capacities expressed in powers of 2 .

 

Starting at the beginning , in Paralello in 2 steps

prefix value 

2^1    2 B     1 byte
2^2     4
2^3     8
2^4     16
2^5     32
2^6     64
2^7     138
2^8     256
2^9     532
1 MiB    2^10     1024     casi 1 MB
2^11     2048
2^2     4096
2^3     8192
2^4     16384
2^5     32768
2^6     65536.
2^7     131072.
2^8     262144.
2^9     524288.
1 GiB    2^10     1048576. casi 1 GB (1024 kiB)

 

Tags: