### Can someone please teach me logarithms?

Question by Bran 10 years ago

### Can someone explain logarithms?

Seeing all of the other math Instructables on here, I was surprised not see one on logarithms. I just want to learn beyond my mundane curriculum. Thanks.

Topic by Bran 10 years ago  |  last reply 8 years ago

### Can using logarithms overcome scope insensitivity bias? Answered

Say you perform the following type of psychology experiment:You describe an undesirable event to people,tell them that X instances of the event can be prevented, andask them what they would be willing to pay in order to prevent those X instances.The responses you get (Y) are not even close to being linear with respect to X, but ratherthe responses are roughly logarithmic. That is, X=ABY, or Y=logB(X/A) for some constants A and B.So does anyone know of an experiment (or real-life situation) where subjects are asked to answer in terms of log(Y) instead of Y? Do such responses show a linear relationship to the corresponding X?

Question by NobodyInParticular 10 years ago  |  last reply 10 years ago

### 'Revolutionary' CO2 maps zoom in on greenhouse gas sources

Researchers now have a better view of where carbon dioxide is being emitted thanks to Vulcan, a research project led by Kevin Gurney, an assistant professor at Purdue. This map shows where CO2 is being emitted in the continental United States in 10-kilometer grids and combines data from sources including factories, automobiles on highways and power plants. The map offers more than 100 times the detail of previous inventories of carbon dioxide. The image displays metric tons of carbon per year per grid in a logarithmic base-10 scale.more at Physorg

Topic by ewilhelm 11 years ago  |  last reply 11 years ago

### spiral clock hands

I want to make a desk clock as a small project for myself. What I am looking to create is a slim clock with a spiral hour hand. The time would be told by graduated marks on the back-plate i.e. as the hour hand turns, the spiral increases and the correct hour is reached by the spiral, hard to explain, can't upload a photo as instructable server maintenance is under-way, hopefully I'll be able to upload the brief sketch I did in paint which might help!! What I am looking for is suggestions on a material which could be used for the hand, it needs to be thin so as to make it as easy as possible to tell the time and also strong enough not to distort under its own weight. Haven't decided whether it's going to be a normally incrementing spiral or a Fibonacci spiral (or similar logarithmic spiral)

Question by johnnie98765 4 years ago  |  last reply 4 years ago

### Looking for a gainclone design that's lower powered than most. What is the equivalent wattage at 16 or 4 ohms?

Most of the gainclone designs i can find are between 25 and 50 watts. I have a pair of 20 watt maximum @ 8 Ohms which I'd like to build a small amp for (possibly portable, but gainclones don't seem to have much of that). The downside: I understand making the Ohms match the minimum required of my amplifier, but I've never had to worry about the max wattage before. I know that if I attach them in series I get 16 Ohms and 4 if parallelled, but trying to figure out what the wattage becomes seems difficult. I know its logarithmic, but I can't find a calculator for it. Plus I think it depends on the amp's output ability. (Yes I did mention these in another question.)

Question by Andale_The_Great 8 years ago  |  last reply 8 years ago

### What potentiometer to use as audio control in car stereo?

Hello all I am working on installing a tablet into my car instead of the original head unit. But since the tablet will be permanently mounted inside the dash, I have no way of turning the volume up or down on the tablet, therefore I need to install a potentiometer into the audio cable that goes into my amplifier.  I have tried with a dual LIN 100kOhm potentiometer, which worked to an extend, but not as well as I had hoped.  It did turn the volume up and down, but it couldn't turn the volume all the way down as I had hoped it would be able to. I just want it to be able to turn up quite loud, but also turn all the way down, so I don't have to pause the music everytime I want it to be quiet.  Cheers! Mathew

Question by Mat_Holm 2 years ago  |  last reply 2 years ago

### Fun Facts about Pi Day

The Pi Day Pie Contest is open until March 31st. Share a pie recipe to win a stand mixer. There's even a special judge's prize for the best pi-themed decoration. This year's Pi Day is special, because it's Pi Day ALL MONTH LONG. The third month of the fourteenth year (3/14) lasts for the duration of March, and it won't happen again for another hundred years. So get baking! Some miscellaneous Pi facts: (1) Pi is the ratio of a circle’s circumference to its diameter. Pie is a baked dish made of sweet or savory filling wrapped in pastry dough. They are often, but not always, circular. Expressed in terms of pie, π is the ratio of the diameter of the pan to the length of the crust. (2) Pi didn’t always have a name, much less a sweet Greek letter of its own. Contemporary use of the π symbol is thanks to mathematician William Jones, who in 1706 proposed using the letter p to indicate perimeter. Leonhard Euler, the same guy who brought you functional notation in the form of f(x), popularized π by including it in his work around 1737. Euler is responsible for many of the letters that bedevil beginning algebra students: i for the square root of -1, e for the base of the natural logarithm, and much of the notation for trigonometric functions. There is a Wikipedia page devoted to the list of things named after him, and it is enough to make an English major blanche in terror. (3) Pi Day is officially a thing, at least in the United States. In 2009, House Resolution 224 officially recognized Pi Day as a holiday on March 14th. Presumably as a kick in the pants for the education system, not as a literal example of political pork. Resolved, That the House of Representatives-- (1) supports the designation of a `Pi Day' and its celebration around the world; (2) recognizes the continuing importance of National Science Foundation's math and science education programs; and (3) encourages schools and educators to observe the day with appropriate activities that teach students about Pi and engage them about the study of mathematics. (4) Pi is vaguely described in 1 Kings 7:23-26 in the King James version of the Bible. Solomon's pool should probably have been 31.4 cubits around, but he deserves some credit for getting pretty dang close. (5) Pie Day is on January 23rd, according to the American Pie Council, but they're still cool with celebrating Pi Day with pies.

Topic by wilgubeast 5 years ago  |  last reply 4 years ago