Studying physics at school lasts several years. At the same time, students are faced with the problem that the same letters represent completely different quantities. Most often this fact concerns Latin letters. How then to solve problems?
There is no need to be afraid of such a repetition. Scientists tried to introduce them into the notation so that identical letters would not appear in the same formula. Most often, students encounter the Latin n. It can be lowercase or uppercase. Therefore, the question logically arises about what n is in physics, that is, in a certain formula encountered by the student.
Most often in school courses it occurs when studying mechanics. After all, there it can be immediately in spirit meanings - the power and strength of a normal support reaction. Naturally, these concepts do not overlap, because they are used in different sections of mechanics and are measured in different units. Therefore, you always need to define exactly what n is in physics.
Power is the rate of change of energy in a system. This is a scalar quantity, that is, just a number. Its unit of measurement is the watt (W).
The normal ground reaction force is the force that acts on the body from the side of the support or suspension. In addition to the numerical value, it has a direction, that is, it is a vector quantity. Moreover, it is always perpendicular to the surface on which the external influence is made. The unit of measurement for this N is newton (N).
What is N in physics, in addition to the quantities already indicated? It could be:
Avogadro's constant;
magnification of the optical device;
substance concentration;
Debye number;
total radiation power.
The list of names that may be hidden behind it is quite extensive. The notation n in physics is used for the following concepts:
refractive index, and it can be absolute or relative;
neutron - a neutral elementary particle with a mass slightly greater than that of a proton;
rotation frequency (used to replace the Greek letter "nu", since it is very similar to the Latin "ve") - the number of repetitions of revolutions per unit of time, measured in hertz (Hz).
What does n mean in physics, besides the quantities already indicated? It turns out that it hides the fundamental quantum number (quantum physics), concentration and Loschmidt constant (molecular physics). By the way, when calculating the concentration of a substance, you need to know the value, which is also written with the Latin “en”. It will be discussed below.
Its name comes from the Latin word numerus, translated as “number”, “quantity”. Therefore, the answer to the question of what n means in physics is quite simple. This is the number of any objects, bodies, particles - everything that is discussed in a certain task.
Moreover, “quantity” is one of the few physical quantities that do not have a unit of measurement. It's just a number, without a name. For example, if the problem involves 10 particles, then n will simply be equal to 10. But if it turns out that the lowercase “en” is already taken, then you have to use a capital letter.
The first of them determines power, which is equal to the ratio of work to time:
In molecular physics there is such a thing as the chemical amount of a substance. Denoted by the Greek letter "nu". To count it, you should divide the number of particles by Avogadro's number:
By the way, the last value is also denoted by the so popular letter N. Only it always has a subscript - A.
To determine the electric charge, you will need the formula:
Another formula with N in physics - oscillation frequency. To count it, you need to divide their number by time:
The letter “en” appears in the formula for the circulation period:
In a school physics course, this letter is most often associated with the refractive index of a substance. Therefore, it is important to know the formulas with its application.
So, for the absolute refractive index the formula is written as follows:
Here c is the speed of light in a vacuum, v is its speed in a refractive medium.
The formula for the relative refractive index is somewhat more complicated:
n 21 = v 1: v 2 = n 2: n 1,
where n 1 and n 2 are the absolute refractive indices of the first and second medium, v 1 and v 2 are the speeds of the light wave in these substances.
How to find n in physics? A formula will help us with this, which requires knowing the angles of incidence and refraction of the beam, that is, n 21 = sin α: sin γ.
Typically, tables give values for the absolute refractive indices of various substances. Do not forget that this value depends not only on the properties of the medium, but also on the wavelength. Table values of the refractive index are given for the optical range.
So, it became clear what n is in physics. To avoid any questions, it is worth considering some examples.
№1. During plowing, the tractor pulls the plow evenly. At the same time, he applies a force of 10 kN. With this movement, it covers 1.2 km within 10 minutes. It is necessary to determine the power it develops.
Converting units to SI. You can start with force, 10 N equals 10,000 N. Then the distance: 1.2 × 1000 = 1200 m. Time left - 10 × 60 = 600 s.
Selection of formulas. As mentioned above, N = A: t. But the task has no meaning for the work. To calculate it, another formula is useful: A = F × S. The final form of the formula for power looks like this: N = (F × S) : t.
Solution. Let's first calculate the work and then the power. Then the first action gives 10,000 × 1,200 = 12,000,000 J. The second action gives 12,000,000: 600 = 20,000 W.
Answer. The tractor power is 20,000 W.
№2. The absolute refractive index of glass is 1.5. The speed of light propagation in glass is less than in vacuum. You need to determine how many times.
There is no need to convert data to SI.
When choosing formulas, you need to focus on this one: n = c: v.
Solution. From this formula it is clear that v = c: n. This means that the speed of light in glass is equal to the speed of light in a vacuum divided by the refractive index. That is, it decreases by one and a half times.
Answer. The speed of light propagation in glass is 1.5 times less than in vacuum.
№3. There are two transparent media available. The speed of light in the first of them is 225,000 km/s, in the second it is 25,000 km/s less. A ray of light goes from the first medium to the second. The angle of incidence α is 30º. Calculate the value of the angle of refraction.
Do I need to convert to SI? Speeds are given in non-system units. However, when substituted into formulas, they will be reduced. Therefore, there is no need to convert speeds to m/s.
Selecting the formulas necessary to solve the problem. You will need to use the law of light refraction: n 21 = sin α: sin γ. And also: n = c: v.
Solution. In the first formula, n 21 is the ratio of the two refractive indices of the substances in question, that is, n 2 and n 1. If we write down the second indicated formula for the proposed media, we get the following: n 1 = c: v 1 and n 2 = c: v 2. If we make the ratio of the last two expressions, it turns out that n 21 = v 1: v 2. Substituting it into the formula for the law of refraction, we can derive the following expression for the sine of the refraction angle: sin γ = sin α × (v 2: v 1).
We substitute the values of the indicated speeds and the sine of 30º (equal to 0.5) into the formula, it turns out that the sine of the refraction angle is equal to 0.44. According to the Bradis table, it turns out that the angle γ is equal to 26º.
Answer. The refraction angle is 26º.
№4. The blades of a windmill rotate with a period of 5 seconds. Calculate the number of revolutions of these blades in 1 hour.
You only need to convert time to SI units for 1 hour. It will be equal to 3,600 seconds.
Selection of formulas. The period of rotation and the number of revolutions are related by the formula T = t: N.
Solution. From the above formula, the number of revolutions is determined by the ratio of time to period. Thus N = 3600: 5 = 720.
Answer. The number of revolutions of the mill blades is 720.
№5. An airplane propeller rotates at a frequency of 25 Hz. How long will it take the propeller to make 3,000 revolutions?
All data is given in SI, so there is no need to translate anything.
Required Formula: frequency ν = N: t. From it you only need to derive the formula for the unknown time. It is a divisor, so it is supposed to be found by dividing N by ν.
Solution. Dividing 3,000 by 25 gives the number 120. It will be measured in seconds.
Answer. An airplane propeller makes 3000 revolutions in 120 s.
When a student encounters a formula containing n or N in a physics problem, he needs deal with two points. The first is from what branch of physics the equality is given. This may be clear from the title in the textbook, reference book, or the words of the teacher. Then you should decide what is hidden behind the many-sided “en”. Moreover, the name of the units of measurement helps with this, if, of course, its value is given. Another option is also allowed: look carefully at the remaining letters in the formula. Perhaps they will turn out to be familiar and will give a hint on the issue at hand.
Global manufacturers of household appliances use color marking of mounting wires when assembling their equipment. It represents the designation in electrics L and N. Thanks to a strictly defined color, the master can quickly determine which of the wires is phase, neutral or ground. This is important when connecting or disconnecting equipment from power.
When connecting electrical equipment and installing various systems, you cannot do without special conductors. They are made of aluminum or copper. These materials conduct electricity well.
These electrical wires are divided into three categories:
To determine which of the conductors is phase and which is neutral using an indicator screwdriver, you need to touch the uninsulated part of the wire with its tip. If the LED lights up, it means that a phase conductor has been touched. After touching the neutral wire with a screwdriver, there will be no glowing effect.
The importance of color marking of conductors and strict adherence to the rules of its use will significantly reduce the time of installation work and troubleshooting of electrical equipment, while ignoring these basic requirements results in a health risk.
N/AN/A, NA, n/a- English abbreviation, usually used in cells of information tables.
Used to indicate the following cases:
Below is a list of abbreviations borrowed from Latin.
In many songs and slangs I see words that are written like this: lovin", chillin" and the rest ending in in". What does this mean and how to translate such words? As I understand it, this is some time ago.
Katarina
It's kind of non-standard. + imitation of pronunciation with an American or Australian accent. This is the ending ing.
ng gives a nasal sound, but is read and pronounced n instead
loving = lovin", an apostrophe (a comma on top) denotes an abbreviation of a word.
loving=lovin"
chilling = chillin".
Blonde in law
[link blocked by decision of the project administration] here is a dictionary in which all slang words and expressions are explained in English. and you can translate what exactly is written there with the help of a translator)))
Fierce
1) he, she, it (about inanimate objects, animals, babies)
She took a quick look at the house and noticed it was very old.
She quickly looked around the house and noticed that it was very old.
2) this, that (about the situation just described)
The day will be fine; no one doubts it.
It will be a great day, no one doubts it.
3) this
What is it? It's a picture. - What is this? This is a picture.
"Who is it?" he asked. - "It"s your neighbor." - "Who is this? " - he asked. “This is your neighbor."
4) in impersonal phrases and vaguely personal sentences
It is snowing. - Snowing.
It's getting dark. - It's getting dark.
It is cold. - Cold.
It is midnight. - Midnight.
It was nice to see you again. - It was nice to meet you again.
5) replaces something as a subject. implied concept
It is three o"clock in the morning. - It is now three o'clock in the morning.
It was Monday, so she was at home. - It was Monday, so she was at home.
How is it in the city? - How are things in the city?
Alexander Zryachkin
ANNO DOMINI (Latin “year of the Lord”) is a chronology that takes as its starting point the probable year of the birth of Jesus Christ. Hence the designations: A.D. - "our era"; B.C. (“before Christ” - “before Christ”) - “before our era”.
AD was proposed by the monk Dionysius the Lesser (died in Rome c. 550); he considered it necessary to abandon the Christian calculus that existed at that time from the Era of Martyrs (its beginning dated back to the year of the accession to the throne of the persecutor of Christianity, the Roman emperor Diocletian - 284). Instead, Dionysius the Less took 753 from the year of the founding of Rome as the year of Jesus' earthly incarnation and the beginning of a new era.
Currently, researchers place the probable year of birth of Jesus Christ between 7 and 4 BC. e. , i.e. at the end of the reign of King Herod (Matthew 2:1) or immediately after his death; another version - during the census period of the province of Syria, when Quirinius was its ruler, namely - 6 BC. e. (Luke 2:2).
This doesn't happen. Or is it poor English?
There are two designations - AD and BC. The first means "AD (Anno Domini - year of the Lord, in Latin)", the second - "BC (before Christ, in English). It is clear that either one or the other is used. The form "before AD" is some kind an incomprehensible construction, most likely an English tracing paper from the RUSSIAN version. That is, our man clearly translated it into English.
Very often in English texts after writing the year you can see the designations B.C. or A.D. Sometimes there is A.C. How is this deciphered?
B.C. - (BC) means before our era (before Christ - before Christ).
A.C. - (BC) which stands for exactly the same: ante Christum (from Latin) BC
A.D. - (AD) anno Domini translated from Latin literally from the year of the Lord, from the birth of Christ, i.e. in the years of our era.
The vast majority of cables have different colors of core insulation. This was done in accordance with GOST R 50462-2009, which sets the standard for marking l n in electrical installations (phase and neutral wires in electrical installations). Compliance with this rule guarantees fast and safe work for a technician at a large industrial facility, and also allows you to avoid electrical injuries during independent repairs.
The color marking of wires is varied and varies greatly for grounding, phase and neutral conductors. To avoid confusion, the PUE requirements regulate what color ground wire to use in the power supply panel, and what colors must be used for zero and phase.
If the installation work was carried out by a highly qualified electrician who knows modern standards for working with electrical wires, you will not have to resort to using an indicator screwdriver or a multimeter. The purpose of each cable core is deciphered by knowing its color designation.
From 01/01/2011 the color of the grounding (or grounding) conductor can only be yellow-green. This color marking of wires is also observed when drawing up diagrams on which such conductors are signed with the Latin letters PE. The coloring of one of the conductors on cables is not always intended for grounding - usually it is done if there are three, five or more conductors in the cable.
PEN wires with combined “ground” and “zero” deserve special attention. Connections of this type are still often found in old buildings, in which the electrification was carried out according to outdated standards and has not yet been updated. If the cable was laid according to the rules, then blue insulation was used, and yellow-green cambrics were put on the ends and joints. Although, you can also find the color of the grounding (grounding) wire exactly the opposite - yellow-green with blue tips.
The grounding and neutral conductors may differ in thickness; they are often thinner than the phase conductors, especially on cables that are used to connect portable devices.
Protective grounding is mandatory when laying lines in residential and industrial premises and is regulated by PUE standards and GOST 18714-81. The neutral grounding wire should have as little resistance as possible, the same applies to the grounding loop. If all installation work is carried out correctly, then grounding will be a reliable protector of human life and health in the event of a fault in the power line. As a result, correctly marking cables for grounding is critical, and grounding should not be used at all. In all new houses, wiring is done according to the new rules, and old ones are put in line for replacement.
For “zero” (or zero working contact) only certain wire colors are used, also strictly defined by electrical standards. It can be blue, light blue or blue with a white stripe, regardless of the number of cores in the cable: a three-core wire in this regard will be no different from a five-core wire or with an even larger number of conductors. In electrical circuits, “zero” corresponds to the Latin letter N - it participates in closing the power supply circuit, and in circuit diagrams it can be read as “minus” (phase, respectively, is “plus”).
These electrical wires require especially careful and “respectful” handling, since they are live, and careless touching can cause severe electric shock. The color marking of wires for connecting a phase is quite varied - you cannot use only colors adjacent to blue, yellow and green. To some extent, it is much more convenient to remember what the color of the phase wire may be - NOT blue or cyan, NOT yellow or green.
On electrical circuits, a phase is designated by the Latin letter L. The same markings are used on wires if color markings are not used on them. If the cable is intended to connect three phases, then the phase conductors are marked with the letter L with a number. For example, to draw up a circuit for a three-phase 380 V network, L1, L2, L3 were used. In electrical engineering, an alternative designation is also accepted: A, B, C.
Before starting work, you need to decide what the color combination of wires will look like and strictly adhere to the chosen color.
If this issue was thought through at the stage of preparatory work and taken into account when drawing up electrical wiring diagrams, you should purchase the required number of cables with cores of the required colors. If you still run out of the required wire, you can mark the wires manually:
About the standards for color marking of wires in Europe and Russia, see also this video:
It is used in cases where during installation it is necessary to use wires with cores of the same color. This also often happens when working in old houses, in which electrical wiring was installed long before the advent of standards.
To avoid confusion during further maintenance of the electrical circuit, experienced electricians used kits that allow them to mark phase wires. This is also allowed by modern rules, because some cables are manufactured without color and letter designations. The place where manual marking is used is regulated by the rules of the PUE, GOST and generally accepted recommendations. It is attached to the ends of the conductor, where it connects to the bus.
If the cable is already connected to the network, then to search for phase wires, electricians use a special indicator screwdriver - its body has an LED that lights up when the tip of the device touches a phase.
True, it will only be effective for two-wire wires, because if there are several phases, then the indicator will not be able to determine which one is which. In this case, you will have to disconnect the wires and use a dialer.
The standards do not require such markings to be made on electrical conductors along their entire length. It is allowed to mark it only at the places of joints and connections of the necessary contacts. Therefore, if there is a need to apply marks on electrical cables without markings, you need to purchase materials in advance to mark them manually.
The number of colors used depends on the scheme used, but there is still a main recommendation - it is advisable to use colors that eliminate the possibility of confusion. Those. Do not use blue, yellow or green marks for phase wires. In a single-phase network, for example, the phase is usually indicated in red.
If you need to determine phase, zero and grounding in three-wire wires, you can try to do this with a multimeter. The device is set to measure alternating voltage, and then carefully touch the phase with probes (you can also find it with an indicator screwdriver) and the two remaining wires in series. Next, you should remember the indicators and compare them with each other - the phase-zero combination usually shows a higher voltage than phase-ground.
When phase, zero and ground are determined, markings can be applied. According to the rules, a yellow-green colored wire is used for grounding, or rather a core with this color, so it is marked with electrical tape of suitable colors. Zero is marked, respectively, with blue electrical tape, and the phase is any other.
If during preventive maintenance it turns out that the marking is outdated, it is not necessary to change the cables. In accordance with modern standards, only electrical equipment that has failed can be replaced.
Correct marking of wires is a prerequisite for high-quality installation of electrical wiring when carrying out work of any complexity. It greatly facilitates both the installation itself and subsequent maintenance of the electrical network. To ensure that electricians “speak the same language,” mandatory standards for color-letter marking have been created, which are similar even in different countries. In accordance with them, L is the designation of phase, and N is zero.
Hi all! Today we will talk again about routers, wireless networks, technologies...
I decided to prepare an article in which I would talk about what these strange letters b/g/n are, which can be found when setting up a Wi-Fi router, or when purchasing a device (Wi-Fi characteristics, for example 802.11 b/g). And what is the difference between these standards.
Now we’ll try to figure out what these settings are and how to change them in the router settings and actually why change the operating mode of the wireless network.
Means b/g/n– this is the wireless network operating mode (Mode).
There are three (main) modes of Wi-Fi 802.11 operation. This is b/g/n. What is the difference? They differ in the maximum data transfer speed (I heard that there is also a difference in the wireless network coverage area, but I don’t know how true this is).
Let's go into more detail:
b- This is the slowest mode. Up to 11 Mbit/s.
g– maximum data transfer rate 54 Mbit/s
n– new and high-speed mode. Up to 600 Mbit/s
So, that means we’ve sorted out the regimes. But we still need to figure out why to change them and how to do it.
Everything is very simple here, let's use an example. Here we have an iPhone 3GS, it can work on the Internet via Wi-Fi only in b/g modes (if the characteristics do not lie). That is, in a new, high-speed mode n it cannot work, it simply does not support it.
And if on your router, the wireless network operating mode will be n, without any mixed stuff, then you won’t be able to connect this phone to Wi-Fi, even if you hit your head against the wall :).
But it doesn’t have to be a phone, much less an iPhone. Such incompatibility with the new standard can also be observed on laptops, tablets, Wi-Fi receivers, etc.
I have already noticed several times that with a variety of problems with connecting phones or tablets to Wi-Fi, changing the Wi-Fi operating mode helps.
If you want to see what modes your device supports, then look at its specifications. Typically supported modes are listed next to “Wi-Fi 802.11”.
On the packaging (or on the Internet), you can also see in what modes your router can operate.
Here is an example of the supported standards that are indicated on the box of the TP-LINK TL-WN721N adapter:
I'll show you how to do this using the example of two routers, from ASUS And TP-Link. But if you have a different router, then look for changing the wireless network mode settings (Mode) on the Wi-Fi settings tab, where you set the name for the network, etc.
On a TP-Link router
Go to the router settings. How to enter them? I'm already tired of writing about this in almost every article :). Better look at this entry https://f1comp.ru/sovety/ne-zaxodit-v-nastrojki-routera/.
Once you are in the settings, go to the tab on the left Wireless – Wireless Settings.
And opposite the point Mode You can select the wireless network operating standard. There are many options there. I recommend installing 11bgn mixed. This item allows you to connect devices that operate in at least one of three modes.
But if you still have problems connecting certain devices, then try the 11bg mixed, or 11g only. And to achieve a good data transfer speed, you can set 11n only. Just make sure that all devices support the standard n.
Using the example of an ASUS router
It's the same here. Go to settings and go to the tab "Wireless network".
Opposite the point “Wireless Network Mode” you can choose one of the standards. Or install Mixed, or Auto(which is what I recommend doing). For more details on standards, see just above. By the way, ASUS displays help on the right where you can read useful and interesting information on these settings.
To save, click the button “Apply”.
That's all, friends. I look forward to your questions, advice and suggestions in the comments. Bye everyone!
