Almonds and Archimedes Principle

Why some almonds float on surface of water while some settle at bottom?

You might have observed, when almonds are soaked in water some of them float on surface of water while some settle at bottom. Why this happens? To understand this you have to understand What is upthrust (buoyancy) force.

Upthrust force (buoyancy):
If you lift a heavy stone by a rope and then dangle it in water you will find it appears to weigh less, this is because of the upthrust of the water on the rock. It is much easier to lift things in a swimming pool – the upthrust of the water helps support them.

Things float because the pressure of the water underneath them pushes up and supports them; in other words, water pressure (upthrust) pushing upward balances weight (the force of gravity) pulling downward. That's one of the reasons why we swim in a horizontal position: spreading the body flat makes it work more like a raft, so there's more upthrust from the water below.

Upthrust is defined as the upward force on the object provided by the liquid because the object has "displaced" some of the fluid. The volume below the water level that is now occupied by the object used to be filled with water and if the object has a different density than water there will be an upward force on the object. If this force is less than the weight of the object the object will sink.

We can calculate upthrust of any fluid on any object by this formula:

Buoyancy = (ρ)(V)(g) =  weight of displaced fluid.   

Here ρ is density of fluid, V is volume of object immersed in fluid and g is gravitational acceleration. It is constant. g=9.80665 m/s² (approx. 10 m/s²).

This is also called principle of floatation and Archimedes principle. Archimedes' principle is named after Archimedes of Syracuse, who first discovered this law in 212 B.C.

Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

—  Archimedes of Syracuse

According to Archimedes principle if an object have greater volume it will accommodate greater upthrust force and if density of fluid increases, it will also cause increase in upthrust force. That’s the reason why a needle sink in water but a ship do not.

For more information:

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Now back to almonds, you might have observed some almonds that are hollow from inside which means they have air inside them, which makes them less dense than other almonds and water. Almonds which are less dense but are same in volume than others, float on the surface of water.

Sources

http://www.schoolphysics.co.uk/age11-14/Matter/text/Upthrust_/index.html

https://en.wikipedia.org/wiki/Buoyancy

http://www.explainthatstuff.com/swimming-science.html

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CPU and Cores - Comparison

Clock Speed vs. Cores
CPUs have a clock speed – think of it as how fast the CPU does work. (That’s actually an imperfect analogy as the truth is a lot more complicated, but it will have to do for now.)
For example, Intel’s Core i5-3330 processor has a clock speed of 3 GHz and is a quad-core processor, which means it has four cores. All four cores in this Intel i5 processor are each running at 3 GHz.
Doubling The Cores Doesn’t Double The Speed
Many computer programs are single-threaded, which means that their work can’t be divided across multiple CPUs. They must each run on a single CPU. This means that doubling the cores won’t double their performance.
If you have a single-threaded application running on a 3 GHz quad-core CPU, that application will run at 3 GHz — not 12 GHz. It will use one core and the other three cores will sit idle, waiting for other tasks to perform.
Writing properly multithreaded applications that can scale across several CPUs at once is actually a difficult problem in computer science. It’s becoming a more crucial problem, as the future looks to be computers with more and more cores instead of fewer cores at faster and faster speeds.
Some applications can take advantage of multiple cores. Google Chrome’s multi-process architecture allows it to perform actions across several different cores at once. Some computer games can divide their calculations across multiple separate cores at once.
However, most of the applications you use are likely single-threaded. A quad-core CPU won’t run Microsoft Office twice as fast as a dual-core CPU. If all you do is run Microsoft Office, the performance might be extremely similar.
More cores help if you’re looking to do more at once or if you have a multithreaded application that can take advantage of them. For example, if you’re running several virtual machines while encoding video, extracting files, and doing other CPU-demanding things on your computer, an octo-core CPU may be able to keep up while even a quad-core CPU may stumble under such load.
Dual Core, Quad Core & More
Phrases like “dual core,” “quad core,” and “octo core” all just refer to the number of cores a CPU has:
• Dual Core: Two cores.
• Quad Core: Four cores.
• Hexa Core: Six cores.
• Octo Core: Eight cores.
• Deca Core: Ten cores.
Controlling & Monitoring Cores
You can actually control which running programs can use a core from the Windows task manager. Right-click a process on the Processes pane and select Set Affinity.

You’ll be able to select which physical CPUs (cores) the application can run on. You shouldn’t need to tweak this most of the time, although it can be helpful when you want to restrict a demanding application to certain cores or avoid bugs in old PC games.

From the task manager, you can also use the Performance tab to view the usage of all your CPU cores.

You can see no. of cores in taskbar of windows 8.1 in older windows follow this method
Open a command prompt by pressing Windows Key + x + a and paste in the following command:
WMIC CPU Get /Format:List

Scroll down and look for NumberOfCores and NumberOfLogicalProcessors.  From the graphic above you can see I have a quad core processor
Hyper-Threading
Intel CPUs use a technology referred to as “hyper-threading technology.” With hyper-threading, each physical core presents itself to the system as two logical cores. In the screenshot above, we’re not using an octo-core CPU – we’re using a quad-core CPU with hyper-threading.
This improves performance to some degree, but a quad-core CPU with hyper-threading is nowhere near as good as an octo-core CPU. You still only have four physical cores, although some tricks allow them to do a bit more work at once.
 Sources :
http://www.fixedbyvonnie.com/2014/04/can-tell-many-cpu-cores-windows-8/
http://www.makeuseof.com/tag/what-does-dual-core-and-quad-core-mean-makeuseof-explains/ 

Electrochemical cells, Difference between electrolytic and galvanic cell.

How to identify anode and cathode in a cell?

Electrode at which oxidation occurs is anode and at which reduction occurs is cathode or we can say that "electrons move from anode to cathode no matter what charge each electrode have."

Electrodes & Charge                                                                      The anode of an electrolytic cell is positive (cathode is negative), since the anode attracts anions from the solution. However, the anode of a galvanic cell is negatively charged, since the spontaneous oxidation at the anode is the source of the cell's electrons or negative charge. The cathode of a galvanic cell is its positive terminal. In both galvanic and electrolytic cells, oxidation takes place at the anode and electrons flow from the anode to the cathode. 

Galvanic cell

Now, in galvanic cell the reaction proceeds without an external potential helping it along. Since at the anode you have the oxidation reaction which produces electrons you get a build-up of negative charge in the course of the reaction until electrochemical equilibrium is reached. Thus the anode is negative.

At the cathode on the other hand you have the reduction reaction which consumes electrons (leaving behind positive (metal) ions at the electrode) and thus leads to a build-up of positive charge in the course of the reaction until electrochemical equilibrium is reached. Thus the cathode is positive.

Electrolytic cell

In an electrolytic cell you apply an external potential to enforce the reaction to go in the opposite direction. Now the reasoning is reversed. Electrode connected to the negative end of the battery will have negative charge or excessive electrons .These excessive electrons will cause reduction in this electrode. So the negative electrode will be the one where the reduction reaction will take place and thus it's the cathode.

At the positive electrode where you have produced a low electron potential via an external voltage source i.e. positive pole of battery, will cause oxidation. So the positive electrode will be the one where the oxidation reaction will take place and thus it's the anode. Refer to the figure:

Differences between Galvanic cell and Electrolytic cell

Electrochemical cell (Galvanic Cell)	Electrolytic cell
A Galvanic cell converts chemical energy into electrical energy.	An electrolytic cell converts electrical energy into chemical energy.
Here, the redox reaction is spontaneous and is responsible for the production of electrical energy.	The redox reaction is not spontaneous and electrical energy has to be supplied to initiate the reaction.
The two half-cells are set up in different containers, being connected through the salt bridge or porous partition.	Both the electrodes are placed in a same container in the solution of molten electrolyte.
Here the anode is negative and cathode is the positive electrode. The reaction at the anode is oxidation and that at the cathode is reduction.	Here, the anode is positive and cathode is the negative electrode. The reaction at the anode is oxidation and that at the cathode is reduction.
The electrons are supplied by the species getting oxidized. They move from anode to the cathode in the external circuit.	The external battery supplies the electrons. They enter through the cathode and come out through the anode.

Examples:

In the following examples, the anode is positive in a device that consumes power, and the anode is negative in a device that provides power:

• In a discharging battery or galvanic cell (diagram at right), the anode is the negative terminal because it is where the current flows into "the device" (i.e. the battery cell). This inward current is carried externally by electrons moving outwards, negative charge moving one way constituting positive current flowing the other way.
• In a recharging battery, or an electrolytic cell, the anode is the positive terminal, which receives current from an external generator. The current through a recharging battery is opposite to the direction of current during discharge; in other words, the electrode which was the cathode during battery discharge becomes the anode while the battery is recharging.