Electric Current – Definition, Types and Effects

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Electric current is when there is a motion of charges from one place to another. The two objects having different potential linked with the same wire move electrons from point A to point B. the current stops flowing once both the objects reach the same potential.

The current only runs in the presence of potential differences in the conductor. This physics division deals with motion charges and forms the current electricity.

Electric Potential is the total work required to facilitate the movement of charge from point A to point B going against the electric field. This leads to the gaining of electric potential energy by the object.

The calculation of this energy is by dividing potential energy by quantity of charge. The electric field strength is also dependent on the potential which is a scalar quantity.

Electric field lines begin at a positive charge and end at a negative charge. They go parallel with the field and their density decides the field magnitude as well. The smallest unit charge for them is 1.6021 x 10-19 Coulomb. Q or q denotes the charge in these lines.

Electrostatics is the branch of electricity that deals with stationary or slow-moving electric charges. It is due to the force that charges exert on each other though it’s a bit weak.

Coulomb’s Law of Electrostatics

Coulomb’s law states that “the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects”.

The formula for the law is

F = k \frac(q1q2)(r^2)
(F – electric force, K – Coulomb constant, q1, q2 – charges, and R – a distance of separation)

Limitations of Coulomb’s Law

  • This law applies only to charges that are at rest.
  • The inverse law of square needs to be obeyed for the application of this law.
  • It is difficult to apply for arbitrarily shaped objects as the distance between charges is hard to find out.
  • It does not apply to calculate charges on the big planets.

Positively and Negatively Charged Particles

The positively charged particles have more number of positive ions compared to negative ions. Simply put, the number of protons > number of electrons. To neutralize these particles, surrounding electrons enter the particle until both of them are equal.

In the case of negatively charged particles, the number of electrons > number of protons. But to neutralize this particle, electrons move out till the number is equal. This is because protons are not capable of moving.

Neutral particles have equal numbers of protons and electrons.

Electrostatics Examples

  • The plastic package sticking to your hand is due to electrostatic attraction.
  • A charged scale attracts scale.
  • The spontaneous explosion of grain silos
  • Manufacturing damage of electronic components
  • Operation of Photocopier & laser printer

Electrical Conductor

The materials that allow an electric current to flow through them are conductors. After comparing the two materials, the materials that allow a better flow of electricity becomes a good conductor of electricity.

Conductivity is the property of such materials to conduct electricity. There is less resistance as there is an easy transfer of charges in the material.

Some examples are –

  • Copper
  • Aluminum
  • Silver
  • Gold
  • Graphite
  • Platinum
  • Water
  • People

Types of Conductors

1. Metals
Metal is the most common conducting material for application purposes. Wire in households is usually made of copper conductors or alloys. Even the electric plugs and electric irons have metals for conduction. They facilitate flexible mobility of electrons.

The best conductors are Silver, Copper, and Gold. Silver is more expensive than copper thus copper is mostly present in household appliances. Aluminum is another good conductor and often combines with copper in appliances.

2. Non – Metals
Even nonmetals have good conductivity in some cases. One of them is graphite which is a carbon form with 3/4 carbon atoms for bonding. One of them is free for bonding. Other nonmetals are not good electricity conductors.

3. Ionic Conductors
When conductors are present in soluble form, they become ionic conductors. Saltwater is an example here with good electricity conduction. Even conductivity in water is directly affected by the ion content in it.

Electrolytes are the compound that dissolves into ions and increases the conductivity. This is why distilled water shows low conductivity and seawater has higher conductivity. Pure water is bad while normal water acts as a good conductor due to the presence of minerals.

4. Semiconductors
Semiconductors by the name suggest weal conduction of electricity but they have other uses which makes them important. Germanium (Ge) and Silicon are two examples of semiconductors.

5. Superconductors
They are the exact opposite of semiconductors and have zero resistance to the flow of electrons.

Heike Kamerlingh Onnes discovered this phenomenon in 1911. They are usually metallic alloys that below a given temperature loss of resistance property thus becoming superconductors. Some examples are – niobium, cuprate, magnesium, etc.

6. Lighting Conductor
A thick copper wire set up on the highest point of the building to a copper earth pole is a lightning conductor. This is to protect the structure from lightning shocks and provide a path for the current to flow to earth directly.

In the case of direct lighting, the current often melts the conductor but the building damage remains low.

Properties of Electrical Conductor

  • Movement of electrons and ions
  • The electric field of a conductor is zero
  • The charge density is zero too
  • A free charge is present on the conductor surface only
  • There is the same potential at all points of a conductor

Capacitor

An electric device that can store electric charges is a capacitor. It has two conductors for electricity placed at some distance. And this distance has insulating material called dielectric or vacuum. Capacitance is the property of storing charges by the capacitor.

They usually hold energy by holding pairs of opposite charges mostly in a parallel design plate. The types of capacitors vary with styles, lengths, girths, and many materials.

Electrical Current

Above we saw what an electric current is in physics. It mostly works on the movement of electrons and ions in some cases. Ampere is the SI unit to measure it.

Metals have electric wires and other equipment to facilitate current flow in the materials. There are exceptions in some cases where the protons carry a positive charge in opposite flows of electrons. This is mostly in semiconductors.

In some materials, the positive and negative ions coexist. This causes confusion in the electric current flow. The convention of current flow says that current flow opposite to electrons is in a positive direction.

Types of Electrical Current

Types of electric current

There are two main Electrical Current types-

1. Direct current (DC)
The flow of electric current is only in one direction. This current is the easiest to store and mostly used in batteries. Electrons like computers, telephones, satellites, and more follow the direct current approach.

2. Alternating current(AC)
The flow of electric current changes direction and keeps moving to and fro. This is common in household current as it changes 50 times a second. This is why we see 50Hz written on electric devices or equipment.

Electric Cell and Power

A device that converts chemical energy into electrical energy is an electric cell. There are two metal terminals with one positive and one negative. They have a connection to the flow of electric currents. And the rate at which work is done in a circuit is the electric power.

It is the time of transferring electrical energy per unit time. P denotes the electrical power WAtt is its measurement unit. It is a scalar quantity and with the formula –

P = VI ( V – potential difference and I – electric current )

Specific Resistance

When the voltage is applied, resistance offered per unit length is specific resistance. The mathematical representation is –

ρ = RAL
(⍴ – specific resistance, R – resistance, A – cross-sectional area, and L – length of the material)

It is exactly the opposite of specific conductance which is the electrical conductivity of a material. 𝛋 denotes the specific conductance. ohm meter (Ωm) is the SI unit of specific resistance and the table below will show special resistance in different materials.

MaterialSpecific resistance at 20 °C
Silver9.8
Copper10.37
Gold14.7
Tungsten33.2
Steel95.8

Electric Resistivity

Electric resistivity is the ability of a material to oppose the electric flow. It is just like specific resistance. The SI unit for both is the same as well and the denotation of electric resistivity is “⍴”.

Ohm’s Law

Ohm’s law talks about the relationship of an electric current to the potential difference. The assumption is that the current flowing in the conductor stays directly proportional to the applied voltage.

Georg Simon Ohm was a German physicist behind this law. This means that other factors like physical conditions and temperature must remain constant. CFL bulb is an example that violates this law as a change in temperature leads to an increase in current in it.

Ohm’s law states that” the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature remain constant”.

The equation for the law is –
V = IR ( V – voltage, I – current and R – resistance)

Ohm’s Law Applications
  • Determining the voltage, resistance, and current of a circuit
  • Maintain desired voltage drop in electronic components
  • DC ammeter and DC shunts use it to divert the current
Limitations of Ohm’s Law
  • The unilateral electrical elements don’t apply this law as there is one direction flow only. Examples of this are diodes and transistors.
  • Non-linear electrical elements have disturbing current and voltage aching it difficult to apply the law.

Thermal Effect of Electric Current

The passing electric current produces heat in the conductor due to hindrance by the conductor. This leads to the generation of heat inside the conductor and there is a thermal effect or heat effect of the electric current. We use this phenomenon in our day to day lives.

Some application are –

1. Electric Iron
The electric irons have an insulator called Mica that is present between the metal part and the iron coil. The current heats the coil which transfers to the metallic part by the mica. Heating of the metallic part, in turn, helps in ironing the clothes.

2. Electric Bulb
The bulb has tungsten made wire and an inert environment full of neutral gas or vacuum. When the current flows through the wire the heat generates and emits light. The electric power in the bulb comes from heat energy that later converts into light energy.

3. Electric Heater
Nichrome is a high resistance metal present in the generator wire. The coil has an outer layer of ceramic. The current flow generates heat inside the coil which helps in heating cooking vessels.

4. Electric Fuse
The excess flow of heat often leads to the burning of a coil and thus fire. A conducting wire with a low melting point has multiple series of connections that help to avoid burning. Excess heat burns the wire and breaks the circuit avoiding accidents.

Magnetic Effect of Electric Current

Magnetic dipoles create a magnetic field around them that exerts a force. This phenomenon is an electromagnetic effect. The changing magnetic field produces voltage and thus current enabling electromagnetic induction.

This is possible when the conductor is in the magnetic field whether in motion or stationary.

The experiment by Faraday recognized two factors affecting voltage production. They were the number of coils and their direct proportion to voltage. The more turns, the more voltage.

The second factor was changing magnetic fields and their movement around the conductor. The experiment used magnets and electric circuits to study the factors.

Applications of Electromagnetic Effect
  • The AC generator follows this principle
  • The working of electrical transformers
  • The magnetic flow meter
  • Electric motors

Chemical Effects of Electric Current

When a conduction solution sees electric flow there is a chemical reaction between them. Some examples of chemical effects of electric current are – Gaseous bubbles on electrodes and change of color of different solutions.

Not all are good conductors but some of them are.

LiquidConduction 
Lemon JuiceGood 
VinegarPoor 
HoneyPoor 
MercuryGood 
Soda CompoundsGood 

Electroplating

When a layer of metal deposits on other material by the electric current reaction, it is electroplating. The correct electrode and electrolyte are very important for this reaction. For gold deposition on a material, an electrolyte containing gold has to be present.

Applications of Electroplating

  • Jewelry imitation by applying gold or silver on another material
  • Bicycle and motorcycle parts have chrome plates
  • Tin cans have electroplated iron
  • Electric poles have zinc layers electroplated outside
  • Metal extraction from ores.
  • Prevent corrosion by anodizing

Elements of Domestic Supply of Electricity

The electric circuit facilitates the supply of electricity for domestic use. This network has wires, batteries, and other components for the flow of electrons. The start point of electrons is the source and the leaving part is the return. Every component of the circuit has a symbol to represent them.

Electric Circuit Symbols

A power source, conductor, switch, and load is present in a simple circuit. The cell acts as a power source. The load is the resistor made up of copper without insulation.

The wire ends are connected to the load and the source. The switch is the small gap to facilitate the opening and closing of a circuit.

Electrical circuit representation

Conclusion

The concept of electricity is an everyday phenomenon that we come across in our daily lives. This makes electricity very important for general science modules and a basic physics module.

Some important topics were the electric current, ohm law, effects of electric current, and much more. This topic is important for examinations like UPSC, RRB, SSC, etc.

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