Simple electrical circuit , its terms & Effects of electric current

 

Simple electrical circuit and its elements

Simple electric circuit: A simple electrical circuit is one in which the current flows from the source to a load and reaches back the source to complete the path. The electrical circuit should consist of the following.

 • An energy source (cell) to provide the voltage needed to force the current through the circuit.

• Conductors through which the current can flow.

• A load (resistor ‘R’) to control the amount of current and to convert the electrical energy to other forms.

• A control device (switch ‘S’) to start or stop the flow of current.

 

There are three types of electric circuit such as

1.      Closed circuit: The complete path for flow of electric current through consuming deices or load is known as closed circuit.

2.      Open circuit: In an open circuit, there is an infinitely high resistance in the circuit. This condition can happen in a circuit when the switch is open. Therefore, no current of flow.

 

3.      Short circuit: If the supply mains connected directly without any load is known as short circuit.

 

Electric current:

Flow of electron through a conductor is known as electric current. Its unit is Ampere and it is denoted as “I”. It is measured by Ammeter or ampere meter.

Voltage:

It is the electrical potential (pressure) between any two live wire or one live wire and earth. Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conductor or path. Its unit is Volt and it is denoted as “V”. It is measured by Volt meter.

Electro Motive Force (EMF):

The force which causes the flow of electron or current in the circuit is known as EMF. Its unit is Volt and it is denoted as “E”. It is measured by Volt meter.

Potential Difference (PD):

It is the difference of electrical potential (pressure) between two point in an electric circuit. Its unit is Volt and it is denoted as “V”. It is measured by Volt meter.

Terminal voltage (p.d):

It is the voltage available at the terminal of the source of supply. Its unit is Volt and it is denoted as “V”. It is measured by Volt meter.

Load voltage or voltage drop:

It is the voltage dropped across the component or conductor by the flow of current through the resistance is known as voltage drop. Its unit is Volt and it is denoted as “V_L”. It is measured by Volt meter.

Resistance (R):

It is the property of material which opposes the flow of electric current. Its unit is Ohm (Ω) and it is denoted as “R”. It is measured by Ohm meter.

Conductance:

It is the property of material which allows the flow of electric current or it is the reciprocal of resistance. Its unit is Mho (℧) and it is denoted as “G”.

G = 1/R

Quantity of electricity or charge:

As the current is measured in terms of the rate of flow of electricity, another unit is necessary to denote the quantity of electricity (Q) passing through any part of the circuit in a certain time. This unit is called the coulomb (C). It is denoted by the letter Q. Thus,

Quantity of electricity = current in amperes (I) x time in seconds (t) or Q = I x t

Coulomb:

It is the quantity of electricity transferred by a current of one ampere in one second. Another name for the above unit is the ampere-second. A larger unit of the quantity of electricity is the ampere-hour (A.h) and is obtained when the time unit is in hours.

1 A.h = 3600 Asec or 3600 C

Direct Current (D.C):

DC (direct current) is the unidirectional flow or movement of electric charge carriers or DC is a supply whose magnitude and direction remains constant with respect to time. It is denoted as DC ( −− ). Its polarity is Positive (+) and Negative (-).The most common sources of DC supply are the cells/ batteries, DC generators (dynamos) and solar cell.

Alternating Current (A.C): ~

Alternating current is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast or AC is a supply whose magnitude and direction changes with respect to time.

Effects of electric current

When an electric current flows through a circuit, is judged by its effects,

1.       Chemical effect When an electric current is passed through a conducting liquid (i.e. acidulated water) called an electrolyte, it is decomposed into its constituents due to chemical action. The practical application of this effect is utilized in electroplating, block making, battery charging, metal refinery, etc.

2.      Heating effect When an electric potential is applied to a conductor, the flow of electrons is opposed by the resistance of the conductor and thus some heat is produced. The heat produced may be greater or lesser according to the circumstances, but some heat is always produced. The application of this effect is in the use of electric presses, heaters, electric lamps, etc.

3.      Magnetic effect When a magnetic compass is placed under a current carrying wire, it is deflected. It shows that there is some relation between the current and magnetism. The wire carrying current does not become magnet but produces a magnetic field in the space. If this wire is wound on an iron core (i.e. bar), it becomes an electro-magnet. This effect of electric current is applied in electric bills, motors, fans, electric instruments, etc.

4.      Gas ionization effect When electrons pass through a certain gas sealed in a glass tube, it becomes ionised and starts emitting light rays, such as in fluorescent tubes, mercury vapour lamps, sodium vapour lamps, neon lamps, etc.

5.      Special rays effect Special rays like X-rays and laser rays can also be developed by means of an electric current.

6.      Shock effect: The flow of current through the human body may cause a severe shock or even death in many cases. If this current is controlled to a specific value, this effect of current can be used to give light shocks to the brain for the treatment of mental patients.