What is Electricity? [Published]
Daktologist
Global Moderator
What is Electricity?
What is electricity you ask, well as you are about to find out it is an extremely useful form of energy that today’s modern world couldn’t survive without. It lights and heats our homes, makes our phones, computers and internet work, allows you to watch TV and listen to music, fries criminals
and much more. Take a look around you and see how many things require electricity to operate.
First of all what is electrical current?
Electrical current is a flow of electrons through a material. To achieve this force must be applied to the conductor material in order to move the electrons through the conductor. The force is called an electro-motive force (E.M.F) and is provided by sources such as batteries and generators.
A source of E.M.F works by creating captions (a positive charge) at one end of the conductor and anions (a negative charge) at the other end of the conductor. The cations of the E.M.F source which have a positive charge due to the deficiency of electrons attract electrons from the conductor which create a shortage of electrons in the conductor. The conductor in turn attracts electrons from the anions of the E.M.F source, and so a constant flow of electrons occurs from the negative end of the E.M.F source.
Electrical units
Current and charge
Electrical quantity is called charge. The unit of electrical charge (Q) is the coulomb (C) and is equal to 6.24 x 10^18 electrons.
The unit of current (I) is the ampere (A). One ampere is the current flowing in a conductor when one coulomb passes a given point in a circuit in one second. The name ampere is commonly shortened to amp
Power
The unit of power (P) is the watt (W). One watt is defined as the power used when energy is expended at the rate of one joule per second
Electromotive force and potential difference ( Voltage)
Electromotive force and potential difference are generally given the common term of voltage. The unit of voltage is the volt (V)
Resistance
As electrons flow through a conductor they collide with the fixed or static particles. These collisions transfer energy from the electrons and dissipate it in the form of heat. This loss of energy causes the electrons to slow down , so the current in the conductor is reduced. This opposition to current flow is called resistance and is measured in ohms.
Conductance
Resistance in a conductor is the opposition to current flow while conductance is a measurement of the ability of a conductor to pass current and is equal to the reciprocal of the resistance. The unit of conductance is the Siemen (S)
Ohms Law and Kirchhoff's Law
The relationship between current flow and voltage applied to the circuit as well as circuit resistance is defined by ohms law. Ohms law states that:
“The current flowing between any two points in an electrical circuit is directly proportional to the potential difference between these points, and inversely proportional to the resistance of the circuit between these points.”
Which is basically: Voltage = Current x Resistance
Another commonly used law is Kirchhoff’s voltage and current laws which state that:
“The algebraic sum of all currents entering a junction is equal to the algebraic sum of all the currents leaving that junction”
“The algebraic sum of all the voltage drops around a circuit is equal to the algebraic sum of the applied electro-motive forces”
Production of electricity
There are two types of current, Direct current (D.C) and Alternating current (A.C). Direct Current is commonly produced by batteries and is also produced by solar panels and rectified Alternating current (A.C), static electricity and lightning are another example of direct current.
Alternating current (A.C) is commonly produced using rotating machines called alternators which have a coil of wire rotating in a magnetic field.
Alternating current reverses its polarity commonly around 50 or 60 times a second which is measured in Hertz (Hz). Alternating current is used to power your home and everything else that runs on mains power because the voltage can be stepped up or down using a simple electromagnetic device called a transformer to whatever voltage is required for the task at hand.
A.C can also be converted into direct current to run electronic devices like radios and computers using a device called a rectifier which forces the current to only flow one way rather two.
Other ways A.C is produced
An Inverter can convert Direct current into Alternating current and are commonly used for providing power to mains powered devices in areas where mains power isn't available such as in vehicles and remote areas, they are also used for providing A.C power to people who live off the grid and rely on solar or wind to produce power
Comments
This is a resistor.
As you can see, there are several coloured bands around the resistor. These tell us what the resistance of the resistor is. In most resistors, there is a gold or silver tolerance band on one side, and the closest band to it is the multiplier. The rest are digit bands, usually 2 or 3 depending on the number of significant figures known.
Let's see what the code is:
Digit Colours:
Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Violet = 7
Gray = 8
White = 9
Multiplier Colours:
Brown = 10
Red = 10^2
Orange = 10^3
Yellow = 10^4
Green = 10^5
Blue = 10^6
Gold = 10^-1
Silver = 10^-2
Tolerance Colours:
Silver = 10%
First, locate the tolerance band. This is most often the gold or silver band. Start reading the resistor from the other side.
In the given resistor, we start by reading a brown band. Write down a digit value of 1. Then it's a black band. Write down a digit value of 0 for it. The next band is the last band before the tolerance band, so it is the multiplier. Red is a multiplier of 10^2, so we take the digits we have written down, which is 10, and multiply by 100, to get 1000 ohms.
Then we come to the tolerance band. It tells us the accuracy of the code, and the gold band gives us an accuracy of within 5%, so the resistance of the resistor can be anywhere from 950 to 1050 ohms.