12 replies to this topic

[squeaky]

A resistor is an electronic component that reduces electrical current between two terminals because of Ohm’s law. The term resistance occurs when an object blocks the flow of electricity, thus reducing voltage. Many household appliances produce resistance such as the light bulb because of the filament in the bulb. Resistors are objects that specify in resistance to reduce currents for small electronics.
A German physicist, Geog Ohm, was a professor at the college at Cologne in 1817 and in the polytechnic school of Nuremberg in 1833, and in 1852 became professor of experimental physics in the university of Munich, where he later died. He experimented with different types of wires and found that they had different measurements in voltage. He then measured the current with a voltmeter and discovered a measurement in resistance. He then created the symbol (Ω) to show how much resistance an object has on a circuit. Ohm found that the resistance for most conductors does not depend on the voltage across them. A conductor or any other device that has a constant resistance regardless of the voltage is said to obey Ohm’s Law.
There are different types of circuits that create resistance parallel circuits and series circuits. In parallel circuits, they are used in branching off other circuits, making the two circuits one big one. The series circuits are used to connect several light bulbs, but decreasing their brightness; if one light bulb burns out the current will keep on flowing, lighting the other light bulbs in the process.
Electrical circuits are a complete path through which electric charges can flow. All electrical devices, from computers to radios to televisions, contain resistors to keep resist certain amounts of voltage for each component of the device. Resistors can be thought up as a freeway, which has been interrupted from an accident on the road; the flow of traffic would be decreased. In the process of using resistors, they create heat and require different sizes for different voltages.

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[bhavesh]

A good tutorial even though it is copied.

Quote

All electrical devices, from computers to radios to televisions, contain resistors to keep resist certain amounts of voltage for each component of the device.

As said above resistors are used in every electrical component. Let me explain you the problem of not using it.

According to Ohms law,
Current(I) = Voltage(V) / Resstance, R

So when resistance is not present i.e. R=0, then current will become infinite and an infinite current will damage your euipment. So resistors are must.

Edited by bhavesh, 10 September 2006 - 04:52 PM.

[darran]

In other words, judging by the mathematical formula you presented, a resistor will reduce the voltage by several folds depending on the type of resistor being used? However judging by Math alone, any number which is divided by 0 will be a mathematical error because no number can be divided by 0. So how does infinite come about?

[SGCHS]

It seems to me per the formula, that without resistance, you only have voltage.

It is not 0 resistance that will cause problems, but resistance that is less than one.

So as the resistance moves closer and closer to 0, the current begins to climb higher and higher which can then short out your equipment.

Anyway, that is, in my opinion, a very good WAG based on some mathematical facts.

Thank you for taking the time to read this post.

Edited by SGCHS, 09 September 2006 - 02:42 PM.

[hype]

darran, on Sep 9 2006, 09:02 PM, said:

In other words, judging by the mathematical formula you presented, a resistor will reduce the voltage by several folds depending on the type of resistor being used? However judging by Math alone, any number which is divided by 0 will be a mathematical error because no number can be divided by 0. So how does infinite come about?

Well, if a number is divide by 0, it simply means the answer is infinite! And yes, the formula is true and even a wire connecting those power supply has resistance, so you rarely get yourself into an infinite voltage, which will kill...

[bhavesh]

Quote

a resistor will reduce the voltage by several folds depending on the type of resistor being used?

Not at all, infact voltage is constant and current varies. Unless you use a variable voltage source.

Quote

However judging by Math alone, any number which is divided by 0 will be a mathematical error because no number can be divided by 0. So how does infinite come about?

Any number when divided by a number which is less than 1 will increase the result, example,
2 / 0.5 = 4
and 2 / 0.25 = 8
i.e. answer is increasing as the denominator is reducing and will eventually be infinite when denominator is zero.

Quote

It is not 0 resistance that will cause problems, but resistance that is less than one

No, resistors less than 1 are also used in circuits, they are required where we require high current, by using low voltages. And zero resistance will short circuit the equipment.

Resistors are used to determine how much current is to be drawn from the voltage source. The voltage in our house is constant and all the equipments in the house are connected in parallel. Every equipment's power rating is different and power is given by the formula
Power, P = V * I
So as the voltage is constant, therefore to get different powers current should be varied and to vary current, resistance should be varied.

Edited by bhavesh, 10 September 2006 - 04:52 PM.

[darran]

Well I was always taught in high school that a number can never be divided by 0, even the calculator shows you an error. So anything which divides by 0, is infinite or in graphical terms an 90 degrees anticlockwise inverted 8? So it would not be logical to have 0 resistance because that would mean infinite current which could be very dangerous. It is really interesting how Math can teach you how certain calculations of things we can't see really works.

Since the resistor pretty much plays a crucial part in determining the current, are there any resistors which are over 1? From what I understand, resistors are the thrump card to vary currents from circuit to circuit am I right? Each circuit will have a standard amount of current and that is where the varying of the resistance power is decided?

[sportytalk]

I'd like to thank those who have posted information about resistors onto this topic. I knew the basics of what resistors were, what they looked like and the basics of when they would need to be used before reading this topic, however, I only knew the basic facts. After reading this topic and reading the informative threads, I now know a lot more about resistors.

I didn't think of the resistance in the way Bhavesh explained it above, the way of having an infinite current if the resistance is 0, but thinking about it, it all makes sense and I can now see why a resistor is needed.

All the information in here is helpful, resistors are found in neally all the modern electronics that are around nowadays, so it's good that we know about them.

[franz see]

darran, on Sep 9 2006, 01:02 PM, said:

In other words, judging by the mathematical formula you presented, a resistor will reduce the voltage by several folds depending on the type of resistor being used? However judging by Math alone, any number which is divided by 0 will be a mathematical error because no number can be divided by 0. So how does infinite come about?

1. Reduction of Voltage: Partly true. However, take note that it is the voltage drop on the resistor itself that is affected, and not the voltage on of the voltage source
2. Divided by 0 = Infinity: Yes, dividing by zero is undefined. BUT, the limit of (y / x) as x approaches zero is infinity. Knowing this fact allows us to understand better the behaviour of the function.

hype, on Sep 10 2006, 05:01 AM, said:

Well, if a number is divide by 0, it simply means the answer is infinite! And yes, the formula is true and even a wire connecting those power supply has resistance, so you rarely get yourself into an infinite voltage, which will kill...

1. Formula being true: Well, for basic uses yes. But it is merely an approximation.

darran, on Sep 11 2006, 12:50 AM, said:

Well I was always taught in high school that a number can never be divided by 0, even the calculator shows you an error. So anything which divides by 0, is infinite or in graphical terms an 90 degrees anticlockwise inverted 8? So it would not be logical to have 0 resistance because that would mean infinite current which could be very dangerous. It is really interesting how Math can teach you how certain calculations of things we can't see really works.

Since the resistor pretty much plays a crucial part in determining the current, are there any resistors which are over 1? From what I understand, resistors are the thrump card to vary currents from circuit to circuit am I right? Each circuit will have a standard amount of current and that is where the varying of the resistance power is decided?

1. Resistors with value over 1 ohm: Yes, there are. In fact, these are the types of resistor values you would usually use. And moreover, you'd usually use resistor values by the thousands.
2. Varying currents in a circuit: Yes. That is it's main use, and from that, you can use it in several configurations That is why basic electronic usually starts with the ohms law.
3. Standard Amount: Well, more like standard range Even in a DC circuit, noice can sometimes affect your circuit thus causing some problems (of course, there are configurations to fight noise). Furthermore, you would usually see in a data sheet the input current range of a component with respect to other factors.

NOTE TO EVERYONE:
1. ZERO RESITANCE that DOES NOT mean that there are INFINITE CURRENT passing through. It only means that it can allow "infinite" current to pass through, assuming you have a "zero" resistance material.
2. From my experience with electronics. It is not a an "exact" math. You do not design it to be acceptable to only 1 value, but to a range of values.
3. These are just my 2 cents...it's been a long time since I did any electronic projects hehehe

[kawasu]

wow i didnt think you could go into so much detail about resistors lol.. i just see the as little peanut things on circuit boards and such. you guys must be really smart o_o