The two types of soil samples collected for further study are;
Disturbed Soil Sample
As the name implies; the sample is disturbed by the method used in collecting it. Soil samples collected using the auger, percussion or rotary drill, shell or by hand can result in samples in which their natural structure has been substantially interfered with. Such samples are therefore generally useful for determining moisture content and visual grading.
Undisturbed Soil Sample
These are samples removed by methods which preserve as far as possible the natural structure and properties of the soil material. Methods of collecting undisturbed samples include, by hand, core drilling.
Of the two types of soil samples discussed so far, the undisturbed soil sample gives the best test results.
Power Banks are used to provide electrical power to your phones, laptops, camcorders and handheld electrical devices. They are hand held batteries you can use to charge and power your devices when traveling, off grid areas or places with epileptic power supply.
Choosing a suitable power bank
Power Banks come in various shapes and sizes. Now a very simple rule: The bigger and denser a power bank is, the more capacity it probably has. Battery capacity means how long it can power your device or how many times it can charge your device from zero to 100%. The battery capacity should be boldly written on the packaging of any power bank you intend to buy.
When shopping for a power bank, take a good look at its capacity. It is usually expressed as something mAh. For instance, power Banks can come in capacities of 5000mAh, 10000mAh, 20000mAh and so on.
Also the power rating and battery capacity of the devices you will use the power bank with, matters.
For example, let’s say someone bought you a power bank with a capacity of 10000mAh. And you will be using it to charge a Samsung note 8 phone with a battery capacity of 3300mAh. Theoretically, the power bank should be able to charge the phone from 0-100%, 10000/3300 times or 3.03 times. However because it will be around 85% efficient when new, it should charge the phone atleast 2.5times.
Buying an original power bank
When buying an original power bank, look for the originality, look at the brand name, the packaging, engravement of the brand name and logo on the body of the power bank.
The buying of fake and substandard materials cannot be overemphasized. Most power Banks are made with lithium technology. These lithium batteries are usually purchased brand new in standard sizes from merchants and then used to build power Banks of various capacities.
Some power bank makers can cut corners by buying and using used lithium batteries to build power Banks for sale.
How long your power bank can last
How long your power bank will last depends on the number of charge and discharge cycles it can afford before it becomes unusable. It depends on the type and quality of the lithium batteries.
Power banks made with lithium polymer batteries should at least have a charge-discharge cycle of around 200 times,
Those made of lithium ion at least 300times and those made of lithium phosphate batteries about 1000 times or more. This means a good power bank can last you for more than a year if properly used. Some power Banks can last for 2 to even 4 years.
Care for your power bank
Most power Banks will not last if misused.
When you purchase a new power bank you may be told by the manufacturers to charge it for a certain number of hours before use. Heed this counsel for your batteries to last longer.
Don’t let it drop or fall on the floor, some internal components may become broken or detached which may render it unusable.
Always use the original charger that came with the power bank to charge it.
Don’t let water or other liquids find their way into your power bank.
Don’t put your power bank in a hot room or under direct sunlight.
Don’t charge your power bank or use your power bank to power/charge a device in a hot room.
Do not over discharge your power bank, thankfully most power Banks come with a screen display to monitor the amount of battery power remaining. They are also equipped with circuit boards that prevent over charging and over discharging.
This simple experiment will show the power of frictional force when several sheets of paper are overlapped.
2 notes or exercise books with approximately the same number of pages.
On a table or flat surface, open the 2 books to their last pages and overlap their back covers.
Then take the next pages and overlap each one. Continue doing this until you reach their front covers.
Tell a friend to hold the binding of one book, and you hold the other one.
Try to pull the notebooks apart this way and see what happens.
The books should be very difficult to pull apart.
The surface of paper appears smooth to the naked eye. But when viewed under a microscope it has a rough surface. When 2 or more paper surfaces come in contact, the surfaces interlock due to frictional forces. The frictional forces existing between the paper surfaces makes it difficult to pull the notebooks apart.