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The resistance of a material depends on its length, cross-sectional area, and resistivity. This is expressed by the following equation:
resistance = [(resistivity x length) / cross-sectional area]
So, resistance is directly-proportional to the resistivity and length of the material, and inversely-proportional to its cross-sectional area. So a high resistance can be obtained by increasing the length of the material or by decreasing its cross-sectional area, or by choosing a material with a high resistivity.
It's also worth pointing out that resistivity is affected by temperature. For pure metals, the higher the temperature, the higher the resistivity, so the higher the resisistance. For example, a hot (i.e. an operating) tungsten lamp will have a much higher resistance than a cold tungsten lamp.
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A dangerous circuit with low resistance and high current?
Another name for a circuit with low resistance and high current is a short circuit. It is dangerous because, if you have sufficient energy in the power source, you can damage components and/or cause fires.
Why might the current in a short circuit be higher than the current in the original circuit?
The current in a short circuit may be very high because the resistance in the short circuit is probably less than the resistance in the original circuit.
What would happen to circuit if there was no resistance?
a circuit with no resistance or zero resistance can be considered as open circuit in which the current is zero. without resistance the circuit just becomes open ()
What does ohbr stand for when referring to reyrolle 275 and 400Kv circuit breakers?
Outdoor high pressure break resistance circuit breaker
Is the increase in voltage causes a greater electric resistance in a circuit?
No, the resistance in a circuit does not change when voltage changes. Resistance is an inherent property of the circuit.
When is too high a resistance not a good thing in a circuit?
Too high a resistance is always not a good thing in a circuit. That's what "too high" means.
What is the difference between on and off state resistance?
On Circuit Resistance = Close to the total load Resistance. Off Circuit Resistance = Near Infinitive High Resistance.
How does the loading effect of an ammeter in a low resistance circuit compare to the loading effect in a high resistance circuit?
The voltmeter has an internal resistance, which should be as high as possible. As this resistance draws current from the circuit under test, it will affect circuit operation. This is more pronounced in a high impedance circuit because the current drawn flows through higher resistances.
An open circuit has an infinate resistance?
There is no such a thing as infinite resistance but it could be a very high resistance.
A dangerous circuit with low resistance and high current?
Another name for a circuit with low resistance and high current is a short circuit. It is dangerous because, if you have sufficient energy in the power source, you can damage components and/or cause fires.
Why don't AC input wires to a transformer just short circuit?
The resistance of the winding in the primary of a transformer constitutes a load. As long as there is resistance then there is no short circuit. A short circuit is considered no resistance which develops an instantaneous high current. That is why fuses and breakers are inserted into the circuit to open the high current flow under a short circuit condition.
Why might the current in a short circuit be higher than the current in the original circuit?
The current in a short circuit may be very high because the resistance in the short circuit is probably less than the resistance in the original circuit.
Should all the materials that make up a circuit have high resistance?
No. There should be substantial resistance only where the circuit design needs it and wants it, and as little as possible everywhere else in the circuit.
What are the approximations of open circuit and short circuit tests?
Firstly turn of the power before this test...Using a resistance or continuity tester you should get the following results:Short circuit: Very low resistance (nearly 0 ohms) or the bell will ring.Open circuit: Very high resistance (Somewhere in the range of Mega ohms) or the bell will not ring.The reason for this is because and open circuit has a gap in it (which has high resistance).The short circuit has wires that are crossed and so has a really low resistance.
Will a circuit component with a high resistance will have a low electric current?
Yes
Why does voltmeter have high internal resistance?
No, ammeters have a low internal resistance. This is so that when they are put in series with a circuit, they change the circuit's operating characteristics as little as possible.Contrast this with voltmeters, which do have a high internal resistance, and which are intended to be placed in parallel with the circuit they are measuring.Use the link below to the related question on why ammeters have a low internal resistance and read through that information to see why things are the way they are.
Why does copper have a low resistance?
Because it is a metal so has lots of free electrons which when connected to a circuit detach from the atoms and move around the circuit. This produces a high current, so resistance will be low as current is high.
