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The movement of electrons in matter is called Electron Flow, when electron flow occurs, we call the flow Electricity. In wires, electricity moves easily, this is because metals are good conductors of electricity while non-metals are not.

The path which provides for easy flow of electric current for conversion into useful purposes such as lighting and heating is called an Electric Circuit. 

Electrons can only move through a conductor if there is an electrical potential difference between the two ends of the conductor, and if there is an external source that supplies the electrical energy needed by the electrons to keep moving, e.g a battery or generator.

Potential difference is the work done in moving a unit of positive electric charge from one point to another.

The basic components of electric circuits are:

  1. Source of e.m.f (Battery or generator)
  2. Switch 
  3. Ammeter
  4. Voltmeter
  5. Resistor 
  6. Key 
simple electric circuit
simple electric circuit

The electrons gain energy when they flow through the battery, but lose energy when they flow through the bulb. The reason a light bulb glows is that electricity is forced through tungsten, which is a resistor. The energy is released as light and heat.

The current, made up of electrons, flows through the battery, the light bulb and the wires. The electrons will stop flowing if there is a break in the circuit path, and the bulb will stop glowing.

In a circuit, a switch acts to control the current flow. When it is open the circuit is broken/incomplete and no current can flow, on the other hand when it is closed, the circuit is complete and the current can flow again.

open and closed switch
Open and Closed Switch Symbols.

What we are simply doing is controlling whether the light bulb is on or off, based on the electron flow.

light bulb turnin on and off - electron flow
A light bulb with the switch open and close.

A voltmeter is an instrument used to measure the potential difference of a conductor. The standard metric unit of electric potential difference is the volt(V). It is always connected in parallel across the point at which the p.d is required. 

Symbol for Voltmeter.

An ammeter is an instrument used to measure the flow of current in a circuit. The unit of current is Ampere (A).   

Symbol for Ammeter.
electric circuit
Ammeter and Voltmeter connected in a circuit.


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