Its resistance is low for low potential differences and it rises as the voltage increases and the temperature of the filament rises. Zener diodes are not perfect diodes. No matter how great they are designed, they will always have some value of impedance.
The zener resistance, RZ acts like a small resistance in series with the zener. The effect that the zener resistance has on a zener diode is that small changes in VZ will occur wehn IZ varies. The Zener diode operates just like the normal diode when in the forward-bias mode, and has a turn-on voltage of between 0.
As the reverse voltage increases to the predetermined breakdown voltage Vz , a current starts flowing through the diode. Unlike the normal p-n junction diode, a Zener diode has a low peak inverse voltage. This is an undesirable property for the rectifier circuit. This is the reason why Zener diodes are not used for rectification purpose but are mostly used in applications that require voltage regulation. A Zener diode permits Zener current, Iz, to flow when the voltage is above the specified Zener voltage.
Thus, a Zener diode can be used for voltage detection by sensing Zener current with some other device. Very broadly speaking items made from metals, carbon, and many metal alloys fall into the Ohmic conductors category. The relationship between the voltage current and resistance follows Ohms law - it is linear and can be calculated using Ohms Law. Connecting wire: The connecting wire normally made of copper used for making connections between different electrical and electronic components, etc is an ohmic conductor exhibiting a linear relationship between the voltage across it and the current flowing through it.
Under normal operating conditions, the heat dissipated is low and it remains at a constant temperature. Although the voltage drop along a section of connecting wire will be low, there is nevertheless some resistance and even though the levels of resistance are much lower than for other items, the connecting wire, such as copper wire will still follow Ohm's law.
Resistors : Basic resistors are one of the main electronic components used in electronic circuit designs. In view of the way in which the electronic circuits work, they need to be ohmic and have a linear relationship between voltage and current to ensure the correct functioning of the circuit.
There are many forms of resistor, most of which are ohmic electronic components. They are used within electronic circuit designs to provide a fixed level of resistance within a circuit to set voltages, limit current and the like. There are some forms of resistor that are non-ohmic that are used for some specialised applications.
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. 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.
In an ohmic conductor, the current and the voltage has linear relationship. The current increase or decrease as the voltage is increased or decreased. The non-ohmic conductor has non-linear current-voltage relationship. The current increase with an increase in the voltage.
At constant temperature, the current in a conductor is proportional to the voltage applied across the conductor. If the slope of the V-I graph is constant, the current and voltage has the linear relationship. The slope of the V-I graph can be constant only if the resistance of the circuit remain unchanged. The V-I graph of the semiconductor diode has the exponential relationship. The diode current increases exponentially when the voltage is increased above a particular value.
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