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## Resistance

The resistance of a piece of conductor depends on: material of the conductor, characterized by its resistivity ρ in ohm metre (Ω-m) length of the conductor,  $l$ in metre (m) cross-sectional area of the conductor A in meter square (m²) $$R = \rho \frac{l}{A}$$ The resistivity (ρ) of any object is a property of the material or substance it is made …

## Ohm’s Law

Ohm’s Law states that the ratio of the potential difference across a conductor to the current flowing through it, is a constant, provided that its physical conditions, such as temperature, remain constant. Conductors that give a constant ratio of V to I (i.e. a constant value of resistance) are ohmic conductors(obey Ohm’s law). The resistance of a device is the …

## Potential Difference

The potential difference between two points in an electrical circuit is the electrical energy converted into other forms of energy per unit charge passing from one point to the other. $V = \frac{W}{Q}$ , where V is electric potential difference, W is work done/ energy, Q is charge One volt is the potential difference between two points in an electrical …

## Semiconductors, Electrolyte and Gases

Semiconductors Examples: Carbon, Silicon, Germanium. Carbon is commonly used to make resistors, whereas Silicon and Germanium are commonly used in the manufacturing of transistors and integrated circuits. These are solids which have electrical conductivity between the insulators and conductors at room temperature. The charge carriers are free electrons and holes. Electrical conduction is due to the movement of the free …

## Electrical Conductors and Insulators

Electrical Conductors In metal (eg copper), free electrons are the charge carriers. Electrical conduction in metal is due to the flow of free electrons through a lattice of positive ions The electric field setup by the battery establishes a force on the electrons, making them move in a net direction towards the positive terminal of the battery with a particular …

## Current of Electricity

This topic covers “Current of Electricity” of A Level Physics. (Equivalent to Advanced Placement) If this is too advanced for you, you can try the more basic version here. Sub-Topics Electric Current Electrical Conductors & Insulators  Semiconductors, Electrolyte & Gases Potential Difference Ohm’s Law Resistance  I/V Graph of Metallic Conductor I/V Graph of A Semiconductor Diode I/V Graph of Filament Lamp …