“Resistance means Opposition (Refusal to accept)”
If we make a contact of an iron piece with potential/voltage, iron piece will get the same potential. Further if that same piece get under the potential difference than current will flow through it.
Similarly, If we do a same thing with a Bakelite material than no potential will exist on it & no current will flows under the potential difference. An iron piece provides no opposition to current while a Bakelite provides the complete opposition to current flow.
Here, We can say iron piece has less resistance or no resistance while Bakelite is having a high resistance.
ELECTRICAL RESISTANCE
” Electrical resistance represents opposition to the flow of electrical current under the applied potential difference. For the standardization of electrical resistance, A unit is being introduced which is known as Ohm(Ω). 1 ohm is the resistance offered to 1amps current under the applied potential difference of 1volt. ”
Mainly electrical material is categorized in three categories :
- Conductors
- Semi conductors
- Insulators
- Conductors have less or minimal resistance.
- Insulators have maximum resistance.
- Semi conductors have moderate level of resistance.
Resistance of a material depend upon the type of material; its specific resistance & its physical structure which includes length & Area.
Resistance=Specific resistance ×(Length/Area)
Where,
Specific resistance is the intrinsic property of the material which don’t depend upon it physical structure. It only depends upon the material type. If we choose a same type of material with different physical structure, Its Resistance can be different but its specific resistance remains the same.
Every material whether it is conductor or insulator is having a particular resistance range.
For example Copper & aluminum both are the good conductors having less resistance which means current easily passes through both of them. But aluminum has more specific resistance as compare to the copper.
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APPLICATIONS OF RESISTANCE
“Resistance may sound negative but this can be used in a beneficial way too. It all depend upon the situation, location & how we are using the resistance. “
As discussed above, The two materials conductors & insulators. Conductors have less or minimal resistance while insulators have maximum resistance.
For current conduction, we do need conductor so that current flows smoothly but without insulator; conductor is nothing. Insulators are compulsory to guide the electrical current in defined direction. Both conductors & insulators works hand in hand !
Next, We are going to discuss some of the applications of resistance which completely change our thinking about the resistance.
Resistance behind the heating element
In ovens, cloth irons, radiant heaters & room heaters, Heating element is working. It is the electrical resistance which is behind the heating element. All these heaters are working on the principle of power loss/heat loss which is I²R. Where I is current & R is resistance.
Heat loss is directly proportional to square of current & resistance. More the resistance higher the heat loss.
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Resistor as current limiting element
At PCB cards, We have seen multiple resistors connected. These resistors performs multiple task in which some of the resistors working to limit the voltage or current.
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Voltage tester is the best example of resistor as current limiting device which contains a resistor & a neon bulb. When voltage tester come in contact with the potential, By placing a finger tip at the top of the tester, We are providing the milli-Amps current to flow through the series connection of neon bulb & resistor.
The resistor in series; limiting the current so that current get under the safe value & minimal current flows through the series circuit only to ignite the neon bulb.
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Resistance inside the sensors
Resistance of conductor changes proportional to the change in ambient temperature. Conductor’s resistance increases as temperature increases while Insulator’s resistance decreases as the temperature decreases.
This conductor’s property is used in temperature sensors like ‘thermistors’ & ‘RTDs‘.
For Example At 0°C RTD PT-100 resistance is 100Ω while at 30°C; resistance is 112Ω.
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As discussed above, Resistance depend upon the specific resistance of the material & its physical dimensions like length & area. If changes occurs in the dimensions of conductor, Resistance value of the conductor changes accordingly.
“R=ρ(L/A)Resistance is directly proportional to the length of conductor while it is inversely proportional to the area of the conductor. Resistance increases as length increases while resistance decreases as Area increases.”
This property of resistance; As shape changes their resistance changes; is used in strain gauge which further used in load cells to measure weights.
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CONCLUSION
- The post discusses electrical resistance, which is the opposition to electrical current flow under an applied potential difference.
- Materials are categorized as conductors, semiconductors, or insulators based on their resistance levels.
- The unit of resistance is Ohm (Ω).
- Resistance depends on material type, specific resistance, length, and cross-sectional area.
- Applications include using resistance in heating elements, as current-limiting devices in electronics, and in temperature sensors like thermistors.
- However, resistance can also lead to power loss and voltage drops in circuits.
- Major drawback of electrical resistance is, its Power loss I²R. Whatever the circuit; it is always there. Resistance in the line produces voltage drop in the line.
- Electrical resistance has both the faces; It is equally useful & equally useless. This all depend upon the situations & conditions, How it is coming into the circuit. Unwanted resistance in the circuit create losses in the circuit while in some cases resistances are introduced into the circuit as an application.
Hope, You like the post. If you have any doubt, suggestion or query please do comments!