Electronics Engineering

A conductor is just that - something that conducts electric current. A semiconductor, however, is a material that can be and is used because by doing some things to it, we can cause its resistance to vary dramatically over a fairly wide range of values. We can cause it to conduct with little resistance, and we can cause it to resist current flow completely and prevent current from flowing. The material is a semiconductor, and it "sort of" conducts - either well or poorly or something in between, depending on how the device is made and on what we tell it to do. Conductor will pass electrons by the laws of electrical conductivity. Semiconductor will pass electrons basically only one way.
Conductors, like copper, are materials that simply conduct electricity from point A, such as the negative terminal of a battery, to point B.

Semiconductors are materials that conduct electricity from point A to point B, but have high high resistance. Many conductors can be modified to have unique properties when electricity is applied, such as in transistors. Put simply, semiconductors have an electrical conductivity somewhere between that of conductors (gold, copper) and insulators (wood, rubber).
A conductor allows an electric current to flow through it equally well in either direction. The amount of current which flows depends only on the amount of resistance of the conductor and on the amount of voltage applied across it. The direction of flow can always be considered as being from the positive to the negative pole of the source of the voltage applied, so the direction of flow through a conductor is always determined by which end of the conductor is connected to the positive pole of the source. A semiconductor allows an electric current to flow very strongly in one direction (this is known as the forward current) and very weakly in the opposite direction (which is known as the reverse current). The amounts of current which flow in each direction depend partly on the amount of the voltage applied but mainly on the forward resistance (which is relatively low) and the reverse resistance (which is always very high). So, unlike a conductor, the flow of current through a semiconductor is not the same amount of current whichever way the voltage is applied. The direction in which a semiconductor allows the forward current to flow depends on whether it is a p-type semiconductor or an n-type semiconductor. How are semiconductors made? Certain elements, such as Germanium or Silicon, are not naturally semiconductors but can be made into semiconductors by melting them and adding very small amounts of other chemicals. This process is called doping. Whether a p-type semiconductor or an n-type semiconductor is produced depends on the type of doping chemical used.

Think of it in terms of a central heating system that uses a number of radiators: the water pump applies pressure across all the radiators. But there must also be a pressure difference across the inlet and outlet to each radiator, or water wouldn't flow through the individual radiators. The sum of these pressure differences will equal the pressure delivered across the entire system by the pump.

Now imagine a number of resistances connected in series. There must be individual potential differences across each resistance or current wouldn't flow through them. We call these individual potential differences, 'voltage drops', and the sum of the voltage drops across each resistance will equal the magnitude of supply voltage, but act in the opposite sense.

Power isn't really dissipated in a circuit. It's energythat is dissipated. So the expression, 'power dissipation', really means is the 'rate of energy dissipation'.

So, when an engineer asks, "What is the power dissipation?", what he is actually means is "What is the rate of energy dissipation?"

What is energy dissipation? Well, work is done whenever a current flows through a conductor; this increases the internal energy of that conductor which, in turn, causes its temperature to rise. Because the temperature of the conductor is higher than the surrounding temperature, energy is lost to the surroundings through heat transfer.

* Microcontrollers are sub class of Microprocessor. * Microcontrollers are generally target specific. * For example when the application requirement is to capture 2 analog signals, 5 digital signals, store 512 bytes of data, and to place a time stamp (date & time). Ø Here in the case of processor we need a ADC to process the analog signal, ROM (512 bytes or greater memory size) to store 512 bytes of data, RTC (Real time clock) to get present date and time, of course digital signals can be captured using the I/O port pins, and a RAM also has to be added. This makes the size of the PCB pretty big. Ø In the case of controller all these are found inside it, our task is to select the controller based on the requirement. The microcontroller is basically a processor with some special features like ADC, DAC, RAM, ROM, etc., in it.
microprocessor is able to perform all the task done by micro controller but the microprocessor does not have any timers and counters internally for that operations it need the timers and counters from external. but micro controller can perform all the operations

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An electrical circuit is any closed loop that allows a flow of electrons in a current to deliver energy or perform work and then return to their source.

Material along which electrical current flows freely arecalled conductors. (e.g. copper-wire) The electrons emit and return to an energy supply.

Current is said to flow from positive to negative, because this is the conventional direction of current flow. It is a convention leftover from the when electricity was first discovered.

Electrons actually move through a conductor awayfrom the negative terminal and towards the positive terminal, because of the laws governing electric fields (like charges repel and unlike charges attract). The power-supply produces an EMF (electro-motive-force) that creates the potential difference necessary for electrons to flow freely along a conductor.

The natural force is called Electromagnetism.

Opposite charges attract. An electron will move away from a negative terminal and towards the positive.

In physics it is best to think of the current flow in a metallic conductor as being the overall net flow of negative charge since that is what carries energy This movement is known as net current drift and is slow compared to continual random motion of electrons. That random motion yields no overall displacement over time. Therefore power is neither consumed nor created along a current.