What is the difference between an ideal resistor and a practical resistor? What is the equivalent circuit of a practical resistor?
I work in automotive embedded R n D development of ECUs (electronic control units) . You may consider we design hardware and software for something (cars) similar to the motherboards of you cpu.Ill put it simple, we have something called as worst case calculation for passive components like resistor, capacitor and Inductors. This is what shall answer your practical resistor thing.Based on the temperature mainly resistors have tolerances defined, which means how much the value of resistor will vary from the data sheet specification. There are standard tolerance resistors like 5%, 1% etc. Typically our ecus are designed for export level cars varying countries from Iceland to hot African nations thus the temperature that the Ecu should bear is approx - 40 degree Celsius to 85 degree Celsius in normal operation. Thus the effective temperature of resistors might be more on their surface still the resistors shouldn't completely expand and conduct due to charged ions when heated. The tolerance is this capacity of the resistors to sustain.In crucial electronic designs where resistors are not expected to vary too much 1% tolerance is expected otherwise 5% is a doable design condition.Ideal resistors are the ones where tolerance expected is 0 and the value never varies.
What is the difference between resistance and resistivity?
Although all the answers to date define the various properties none define the basic concept you are seeking.Quite simply the electrical resistance of any material represents the heat dissipated when subject to electromagnetic fields. In electrical circuit theory resistance (R) is a circuit element used to represent the energy dissipated as heat within any material, inductance (L) is a circuit element used to represent energy stored in the magnetic field and capacitance(C) is used to represent energy stored in the electric field. The latter two are how energy is stored, transmitted or propagated by the em fields along conductive materials whereas R is the heat dissipated within the conductor whilst doing so. Any conductive material serves as a waveguide for the propagating em fields which move close to the speed of light.So when a battery or voltage source is used it generates internal heat which is referred to as internal resistance. As such you are correct that the resistance of any wires can be considered its internal resistance.There is no such things as a resistor device as it is a definition intended to represent the heat dissipated within any material when subject to em fields. This is due to the propagating magnetic fields penetrating the surface (skin effect) and the small internal electric field. In a superconductor, which has no resistance, the electromagnetic field does not penetrate the material surface nor is there any internal electrical field, and hence there is no energy dissipated as heat and the (internal) resistance (R) is zero.Finally internal resistance may also be defined as the resistance of the system under consideration such as the Thevenin equivalent of a more complex circuit.Hope this helps.
What is different between diode and resister?
An electric circuit is simply a closed path that connects a source of energy to a load that consumes this energy. When the energy is consumed, the load usually does something that is useful to us, such as provide light or heat (among many many other things).When we connect a source to a load in an electric circuit, electrons flow through the circuit. This flow of electrons is what we call current. These electrons transfer energy from the source to the load. The voltage of the source is a measure of the energy stored in the source.We can make a lot of useful things happen if we can control the flow of electrons in an electric circuit.Let us now consider an analogy for an electric circuit.We have a tank of water, a pipe, and a bucket. The tank is our battery, the pipe is our conducting path, and the bucket is our load.If we want to fill up our bucket quickly, we turn the tap so that more water flows through. Similarly in an electric circuit, resistors control the flow of electric current. A small resistor will allow more current to flow in the circuit, and a large resistor will allow less current to flow through the circuit.There might be a situation where we want water to flow in only one direction. Let's say we want to fill up our water tank using a pump. We will use another pipe to connect our pump to the tank. When we turn the pump on, water flows up the pipe into the tank. When the pump is off, we do not want the water to flow back down the pipe. For this we use something called a valve. It allows water in the pipe to flow only upwards and prevents water flowing down the pipe that is connected to the pump.Similarly, in an electric circuit we may have a situation where we want current to flow only in one direction. For this we use a diode, because it the property of a diode to allow current flow only in one direction, just like a water valve allows water to flow only in one direction.