Both the conductors, whether ohmic and non-ohmic, have their specific functions and purposes. However, ohmic conductors may lose their properties when operated on different ranges so it becomes really important to study their properties before application. In the ohmic conductors, the current and voltage are directly proportional to each other, that is, there is a linear relationship between current and voltage.
In the non-ohmic conductors, the current and voltage are not directly proportional to one another, that is, current and voltage have a non-linear relationship between them. The slope between the current and the voltage in non-ohmic conductors is not straight but a curved line. In non-ohmic conductors, the resistance of the conductors varies according to the variation in the temperature. Examples of ohmic conductors are metals , resistors, nichrome wires, etc.
A recommended experiment for informal assessment is included. You will need light bulbs, resistors, connecting wires, power source, ammeter and voltmeter. Method The two circuits shown in the diagrams above are the same, except in the first there is a resistor and in the second there is a lightbulb.
Set up both the circuits above, starting with 1 cell. For each circuit:. Measure the voltage across the circuit element either the resistor or lightbulb using the voltmeter. Draw two tables which look like the following in your book.
You should have one table for the first circuit measurements with the resistor and another table for the second circuit measurements with the lightbulb. This is a lesson from the tutorial, Electric Circuits and you are encouraged to log in or register , so that you can track your progress. Log In. Register or login to receive notifications when there's a reply to your comment or update on this information.
Don't want to keep filling in name and email whenever you want to comment? Register or login to make commenting easier. Save my name, email, and website in this browser for the next time I comment. Toggle navigation. There are many different types of resistor - their parameters mean that some types are more suitable for particular applications than others.
These are but a few examples of Ohmic conductors and devices. Ohmic conductors and electronic components are the most straightforward of items. There is a surprising number of electrical and electronic components that are non-ohmic. Essentially they exhibit a value of resistance that varies with the voltage applied.
Non-Ohmic conductors are those electrical conductors that do not follow Ohms law. In other words the relationship between voltage and current is not linear for all values. In other words doubling the voltage will not result in a doubling of the current. This can occur for a variety of reasons dependent upon the actual conductor or component in question.
Incandescent light bulb: The incandescent light bulb is a prime example of a non-ohmic conductor response. Although filament lamps, which are also called incandescent lamps, are not widely used these days because they are very inefficient in terms of their conversion of electrical energy to light energy, they are a good example of a non-Ohmic conductor or electrical component.
The reason for the non-Ohmic characteristic results from the heat generated by the filament of the lamp. For normal operation a lamp will be powered by a battery or from the mains power lines. These provide an almost constant voltage and it can be assumed this remains the same all of the time. Initially the lamp has a low resistance, and when the power is applied there is an in-rush of current because of this.
This means that the filament becomes very hot - it is heated to white heat, and this is why it emits light. However the resistance also rises so that the current reduces and the lamp settles to normal operation. As the potential difference across a filament lamp is increased, the current increases and the energy dissipated, as heat, increases, resulting in a filament operating at a higher temperature.
As the temperature increases, resistance of the filament also increases. Semiconductor diode: The semiconductor diode is one of the most obvious non-Ohmic devices that is available.
The basic diode consists of a junction between P-type and N-type material, and the basic action is that only allows current through in one direction. The ideal diode would have no resistance in the forward direction and infinite resistance in the reverse direction. This alone would make it a non-Ohmic conductor, but in reality the situation is more complicated.
In the forward direction, as the potential difference across the device is increased from zero initially little current flows because the current carriers in the PN junction need to have sufficient energy to traverse the junction.
0コメント