According to this model electrical conductors, such as metals, contain charged particles that can be moved from atom to atom relatively easily whereas in poor conductors, insulators, such as ceramics, charged particles are much harder to move. In the scientific model, electric current is the overall movement of charged particles along a continuous conducting pathway. The cause of this movement is usually an energy source like a battery, which provides the force needed to move the charged particles.
Charged particles can pass relatively easily through materials that are good conductors; relatively little electrical energy is needed to create this movement of charge current in such materials.
On the other hand, insulators require considerable amounts of electrical energy to produce similar currents. The electrical resistance of different materials can vary enormously; the resistance of the most widely used conducting materials metals alters with changes in their temperature. The scientific model of electrical resistance is of the moving charged particles colliding with the particles which comprise the structure of the material through which the current is passing.
An energy input is needed to maintain the current because energy is continuously being transformed into heat during these particle collisions. Where the nature of the material is such that collisions are much more frequent, then a greater amount of heat is produced and the electrical resistance is higher.
There are some electrical devices whose functioning depends on this energy transformation, most obviously fan heaters and light globes where the filament of the globe needs to become white hot so that light as well as heat results from the energy transformation.
When we connect such devices into electric circuits we seek to have as little energy conversion as possible as low a resistance as possible in the wires through which the current passes to and back from the device, and an extremely high resistance for materials such as the plastic insulation around the conducting wires that are intended to not have current pass through them.
It is not helpful in trying to explain the much more complicated functioning of currents in fluorescent lights, light emitting diodes LEDs and many complex electronic components. For the mechanical model, the most obvious limitation is that it assumes that all particles are essentially identical and behave in the same way as tiny ball bearings or marbles. In designing electric circuits to enable us to use electrical devices to transform electrical energy we need:. As with both Electric circuits and Making sense of voltage , it is very important to note that the use of quantitative approaches to teach these ideas e.
An approach that is much more likely to promote student understanding is a qualitative approach, one focused by the use of broad questions like:. Explore the relationships between ideas about electrical current, resistance and voltage in the Concept Development Maps — Electricity and Magnetism. Provide a range of prepared materials for students to measure electrical resistance using a bulb, battery and connected test leads as shown here.
These items should be selected to provide two distinct groups of items for students to explore: either very good insulators or very good conductors. The intention is for students to test each material using their bulb and battery to establish if the bulb does or does not light i. The objective is for students to see that most metals are very good conductors and that plastic and ceramics are used widely in the design of electrical hand tools because of their very good insulation properties.
Discuss with students why materials are selected for their insulation properties. Questions for discussion could include:. An alternative approach to this task is outlined in the vignette, Deduce the practical design from limited information which advocates using less teacher direction, encouraging students to exercise greater decision making.
Select a second group of conductors to provide a range of electrical resistances from high to low for the students to test again with a battery, bulb and test wires i. There are many thousands of different types of Resistor and are produced in a variety of forms because their particular characteristics and accuracy suit certain areas of application, such as High Stability, High Voltage, High Current, etc.
In this article, we will see why resistors are an important part of electrical connections and the types of resistors. This attenuation results in electrical energy being lost in the form of heat as the resistor resists the flow of electrons through it. Resistors come in a variety of shapes and sizes. They might be through-hole or surface-mount. They might be a standard, static resistor, a pack of resistors, or a special variable resistor.
In an electronic circuit, the basic function of a resistor is to limit the current to a safe value so that the associated sophisticated parts can function properly.
It may be virtually impossible to build an electronic circuit without involving resistors. Basically the function of a resistor is always to oppose the flow of current through it and the strength of this opposition is termed as its resistance.
German physicist, Sir G. Ohms was able to discover a definite relationship between voltage, current and resistance.
According to him a potential difference or a voltage V across a resistor R is proportional to the instantaneous current I flowing through it and is given as:.
Transistor Biasing: Through one of my previous articles you must have acquired good knowledge regarding transistors. But the base of a transistor is quite vulnerable to high currents, so a resistor is incorporated to limit the current and provide a safe biasing voltage. The value of the base resistor of a transistor may be calculated through the below-given formula:.
A resistor when placed in series with the LEDs regulates a proper flow of current through them. Occasionally resistances less than an ohm are encountered, these are measured in milliohms m thousandths of an ohm.
The reason for this is that the Greek letter omega is not as easy to use as the prefixes R, k, and M. In order that the current can be limited in a particular circuit, a component known as a resistor may be used. Resistors come in a variety of forms from large wired components, or even some using terminals to the very small surface mount components used in many electronics circuits today.
Resistors can be made from a variety of materials, carbon, metal oxide, metal film, resistance wire and the like. Resistors can come in different formats - different types of resistor have slightly different characteristics and this means that they may be used in different circuit applications.
Selecting the right type of resistor can help the circuit operate in the way it is intended. Although a resistor with a 10k resistance will have the same resistance whatever it is made from, characteristics like the temperature stability, noise, long term stability, spurious inductance and the like can be different for different types and this can affect the performance in some circuits. Resistors are used in electrical and electronic circuits for a variety of purposes, but in each case they resist the current flow.
There are many different types of resistor - their parameters mean that some types are more suitable for particular applications than others. When working with any electrical and electronics circuits, it is necessary to know what is resistance and how resistance affects the circuit. In view of the importance of resistance in circuits, resistors are widely used, possibly the most commonly used components in electronics circuits. These components are very easy to use, and the calculations associated with them are normally simple.
Selection of fixed leaded resistors What is resistance? What is resistance Resistance is the hindrance to the flow of electrons in material. Read more about. Ohm's Law. Shopping on Electronics Notes Electronics Notes offers a host of products are very good prices from our shopping pages in association with Amazon.
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