Electric Current: A Fundamental Force in Modern Technology 

Electric current is the flow of electric charge through a conductor. It is a fundamental concept in physics and a cornerstone of electrical engineering. Currents have diverse applications, from powering household appliances to driving complex electronic systems, making them essential in modern technology.

Electric Current Made Simple: Understanding Charge Flow and Ampere Units 

• Meaning: Electric current is expressed by the amount of charge (electrons) flowing through a particular area in unit time.  
  • In other words, it is the rate of flow of electric charges. 
  • The source can be through inverters, a battery, generators etc. and can be used for lighting, heating, cooling and so on.
• Flow of Current: Electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current. 
• Opposite: Conventionally, in an electric circuit the direction of current is taken as opposite to the direction of the flow of electrons (negative charges). 
  • Therefore, if a net charge Q, flows across any cross-section of a conductor in time t, then the current I, through the cross-section is,

I = Qt

• Unit: The SI unit of electric charge is coulomb (C), which is equivalent to the charge contained in nearly 6 × 1018 electrons.
• An electron possesses a negative charge of 1.6 × 10–19 C.

• The electric current is expressed by a unit called ampere (A), named after the French scientist, Andre-Marie Ampere (1775–1836). 
• One ampere:  It is constituted by the flow of one coulomb of charge per second, i.e.

1A = 1C1s

• Small quantities of current are expressed in milliampere (1 mA = 10–3 A) or in microampere (1 µA = 10–6 A).

Electric Circuits: The Journey of Electric Current from Cells to Bulbs 

• Definition: A continuous and closed path of an electric current is called an electric circuit.
  • Electric circuit is the complete path for electricity to pass, from one terminal of the electric cell through the bulb and back to the other terminal of the electric cell. 
• The bulb glows only when current flows through the circuit.
• Sometimes an electric bulb does not glow even if it is connected to the cell. 
  • This may happen if the bulb has fused.
• One reason for a bulb to fuse is a break in its filament. 
  • If the filament of the bulb is broken, the path of the current between the terminals of the electric cell is not completed and hence the current cannot flow. 

Circuit Diagram

• It is a diagram, in which different components of the circuit are represented by the symbols. 
• Circuit diagrams are much easier to draw using symbols.

Electric Potential and Potential Difference

• Potential Difference: For flow of charges in a conducting metallic wire, gravity has no role to play, the electrons move only if there is a difference of electric pressure called the potential difference along the conductor.
• This difference of potential may be produced by a battery, consisting of electric cells. 
• The chemical action within a cell generates the potential difference across the terminals of the cell, even when no current is drawn from it. 
• When the cell is connected to a conducting circuit element, the potential difference sets the charges in motion in the conductor and produces an electric current. 
• In order to maintain the current in a given electric circuit, the cell has to expend its chemical energy stored in it.
• Thus, the electric potential difference between two points in an electric circuit carrying some current as the work done to move a unit charge from one point to the other
  •  Potential difference (V) between two points = Work done (W) / Charge (Q)

               V =  W/Q

• The SI unit of electric potential difference is volt (V), named after Alessandro Volta (1745 –1827), an Italian physicist.

• One volt: One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other. Therefore,

1 volt =  1 joule/ 1 coulomb

1 V = 1 J C–1 

Conclusion
In conclusion, understanding electric current and circuits is like unraveling the magic behind everyday technologies. From the flow of charges to the glow of bulbs, these fundamental concepts play a crucial role in our modern world. Whether it’s the simplicity of a closed circuit or the troubleshooting of a fused bulb, the basics of electric current empower us to navigate and appreciate the wonders of electricity in our daily lives.