Benjamin Franklin said that every substance has an intrinsic property of electricity, which manifested as an electrical fluid.
According to him, high electric fluid meant positively electric and low electric fluid meant negatively electric. Electricity is basically the study of charges or the flow of charges in an electric circuit. It has had a very long history and crazy experiments have been done so far by so many science wizards that today we are able to understand a little bit about electricity in the world of atoms.
Charged particles have an electrical influence in the space around them which is also known as their electric field.
A positively charged particle has an outward field and a negatively charged particle has an inward field.
A test charge is an imaginary unit positive charge which gets influenced in the electric field. It repels from the positive charge and attracts to the negative charge. Basically, like charges repel and unlike charges attract. But what exactly is an electric charge? Charge, in physics, is a physical property of matter which experiences a force when kept in an electromagnetic field. Charge is symbolized by the letter "Q" and its SI unit is Coulomb or "C".
Force experienced by a charge (Q) in a field (E) is similar to the force experienced by a mass (m) in a gravitational field (g).
Interesting Fact:
Electricity is so useful in our day to day life that we can not even explain its importance in one single line. Its evolution for the past many decades has led to many technological innovations and life leisure. A few inventions done in this field include:
1) Electric Motor by Michael Faraday in 1832.
2) Electric Bulb by Thomas Alva Edison in 1878.
3) Portable Handset by Motorola in 1973.
4) Electric Car by Tesla Motors in 2011.
Michael Faraday (Also known as the Father of Electricity)
Electric Terms:
Current, a most commonly used term in electricity is nothing but the amount of electricity or the rate of flow of charges. It is symbolized as "I" and its SI unit is "Ampere" named after the scientist Andre-Marie Ampere who is also known as the Father of Electro-dynamics.
Electric Potential is defined as the work done in bringing a charge from infinity to a point in the electric field. It is symbolized as "V".
Voltage is the intensity of electricity or the difference in electrical potential energy between the two places where the charge is flowing in between of. Voltage is also known as Potential Difference which is basically the work done in bringing a charge from one place to another in an electric field itself. It is symbolized as "V" and its SI unit is simply "Volt" named after the scientist Alessandro Volta.
Interesting Fact:
Alessandro Volta in 1800, created the world's first battery using the voltaic pile. The voltaic pile consisted of a pair of copper and zinc discs piled on top of another which were separated by a layer of cardboard soaked in brine.
World's First Battery created by Alessandro Volta
Electricity:
Electrons are the subatomic particles present in an atom which revolve around the nucleus (as per the latest theories) and have a negative charge. They carry a charge of -1.6 x 10^-19 Coulombs. It takes 6.24 x 10^18 electrons to contribute just 1 Coulomb of charge. See that number! Basically these numbers are reciprocals of one another. We got this big number using the basic formula of total charge.
Total charge (Q) = Number of electrons (n) x Charge on one electron (e).
That is, Q = ne.
The negative charge of an electron is equal in magnitude to the positive charge of a proton which is the smallest possible unit of charge.
In an electrical conductor in a circuit, the greater the potential difference, the more energy is contained in each of the charges. The charges move with a much greater energy.
Since current is the rate of flow of charges, we can derive its formula as:
I = Q / t
By convention, current is equal in magnitude but opposite to the direction of flow of electrons between terminals across which a potential difference is maintained.
Factors Affecting Rate Of Flow Of Charges:
1) The random movement and collision of electrons.
2) The effective drift of electrons.
3) The state at which the atoms of the conductor are in the lattice.
Interesting Fact:
Every point in an electric field has an electric potential.
Greater the current, greater would be the work done. The work done per unit charge is defined as voltage. Voltage is simply the potential energy per charge. 1 volt is the potential difference between two points when 1 Joule of work is done on 1 Coulomb of charge between the two points.
∴ 1 Volt = 1 Joule / 1 Coulomb
or V = W.D / Q
Interesting Fact:
On rubbing a glass rod with a silk cloth, glass rod acquires positive charge and silk cloth acquires negative charge.
Now, amidst all of this, you might have a question as why electrons' flow is known as electricity. Why can't protons flow? Well, the reason is simple as electrons are more loosely bound in conductors and hence can flow if given a little push of energy. Whereas protons are tightly held into the nucleus with neutrons by the binding force of nuclear energy. In metals, there exists metallic bonds where electrons flow in the atomic "glue". They are free and thus flow to create electricity.
Coming back, charges can only exist in integral multiples of "e" on an object where "e" is the charge of an electron or proton with a magnitude of 1.6 x 10^-19 C.
Drift Velocity: Average velocity of electrons moving in a conductor across a potential difference is 2 to 5 cm/hour! That's so slow!
Electrons of metallic atoms are loosely held by their respective atoms. They tend to jump around a bunch of atoms. This is also known a delocalization. The net effect of this random moving of negatively charged particles is zero, and hence no current flows. But, on application of a potential difference, when there is an electric field that forces the electrons to move in a particular direction, these randomly moving colliding electrons gradually shift against the field.
The negatively charged electrons tend to move in the opposite direction of the field. Electric current is the net drift of the randomly moving electrons. These charges move across the cross section at a constant rate for a particular potential difference and a particular characteristic property of a conductor.
Cell: A cell is a device that supplies electrons in excess or builds up charge, more precisely, as electrons across a field triggered by maybe chemical reactions, light interactions or other mechanical means. It creates a potential difference across the circuit thus causing the current to flow.
When there is a possible path for the charges to move from the negative to the positive terminal, only then will the cell be active.
Inside a wire, electric current always flows from a point of higher electric potential, and towards a point of lower electric potential. Electric current does not flow between two points at same potential value.
Interesting Fact:
Given high enough voltage, pressure and temperature, even insulators can conduct electricity. A good example will be lightening.
Electric Circuit:
A circuit diagram is a schematic diagram which shows the components and interconnections of the circuit using standardized symbolic representations. In an electrical circuit, current always moves in a closed path.
The whole set up completing a possible route for the flow of charges from a source of electrical energy through conductors and back is called an electric circuit. It consists of a cell or battery, bulb or resistor, switch and connecting wires.
The points across a cell or battery are referred to as terminals. The bulb in an electrical circuit acts as "load". This is because the electric power being delivered by the battery is consumed by the bulb only or getting converted to light and heat energy by the bulb.
Interesting Fact:
Frequency of direct current is zero.
Let us have a look at a few electric circuit components:
Voltmeter: Device used for measuring electric potential difference between two points in an electric circuit. There is usually some circuit element such as bulb present between the two points.
Ammeter: Device used to measure the current at a point in a circuit.
Galvanometer: An electromechanical instrument used for detecting small currents in the range of microamperes. It also tells us the direction of current. It is very similar to an ammeter and was used back in old times.
Incandescent Bulb: Produces heat and light when current is passed through it.
An ammeter is always connected in series with a device and a voltmeter is always connected parallel with a device. Now what do series and parallel here mean?
Series Combination:
In a series combination in an electric circuit, electric components, such as an ammeter or a resistor, are connected with end to end in contact, such that current flow is equal in all the components in the combination. Series combination can be illustrated as:
Now what are these zig-zag lines in this diagram? These are known as "Resistors".
Parallel Combination:
In a parallel combination in an electric circuit, electric components, such as a voltmeter or resistor, are connected between the same two points, such that the current is divided through each of the resistors according to their resistance. Parallel combination can be illustrated as:
What is this resistor and resistance we are talking about so on? Let us understand more about resistors.
Resistors are devices which dissipate power in the circuit and cause voltage drop across it in the circuit. Therefore, resistors act as consumers in a circuit.
Resistance is the measure of the opposition to current flow in an electrical circuit. It is measured in "Ohms", symbolized by the Greek letter omega (Ω).
Interesting Fact:
Battery is a group of cells connected in a series. Depiction:
Ohm's Law: At a constant temperature, current flowing in a circuit is directly proportional to the applied voltage across the circuit.
Resistance and Ohm's Law is a very deep and interesting topic to explore. We will understand more about it in our next post in the series of electricity.
"The day when we shall know exactly what electricity is will chronicle an event probably greater, more important than any other recorded in the history of the human race. The time will come when the comfort, the very existence, perhaps, of man will depend upon that wonderful agent."
~Nikola Tesla
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