This depends largely on the purpose of a specific resistor in the circuit and may be a trivial calculation or a very difficult calculation that must simultaneously determine the values of several other components (e.g. resistors, capacitors, inductors) in the circuit. Also such calculations rarely give one and only one usable value for the resistor, in which case you must consult the list of available resistor values manufactured and pick the most reasonable ones (also remembering to follow the rule given to Richard Feynman when he was designing mechanical analog computers for the military, before he moved to the Manhattan Project, for selecting gears: "always pick from the center of the catalog, the ones at the beginning and end are harder to make reliably, if they weren't they would be nearer the center and different values would be at the beginning and end").
In rare cases all these techniques may fail and the values of certain resistors may have to be determined empirically by breadboarding the circuit with variable resistors substituted for the ones to be determined. The breadboard circuit is then operated and the variable resistors adjusted until the circuit operates as desired, then the circuit is powered down and the variable resistors removed and measured. Then pick the closest available resistors and reassemble the breadboard with them to verify correct operation with fixed value resistors. If it fails to operate correctly some or all of the variable resistors will have to be reinstalled and different settings found for correct operation, etc.
As an example of a simple circuit where the value of one resistor is impossible to determine without simultaneously determining others is a two resistor voltage divider. You must determine both resistor values, while also taking into account the thevenin equivalent circuit, individual and total power dissipation, whether standard tolerance resistor values are acceptable or if expensive high precision tolerances are needed, etc.
I have actually encountered circuits where a calculation of some component's value proved that no such value exists (e.g. R must satisfy both R > 5K ohms and R < 250 ohms at the same time), in which case the entire design had to be abandoned and a totally different circuit design approach taken.
You can either measure the resistor with an ohmeter, or read the color code printed on most small carbon resistors.
The four band color code is read with the first two colors as numbers and the third as a multiplier by 10^n (n being the number corresponding to the color) and the fourth band (which is separated from the first three) as a tolerance band or quality band.
The colors for resistor values are as follows:
Black 0 (x1)
Brown 1 (x10) 1%
Red 2 (x100) 2%
Orange 3 (x1,000)
Yellow 4 (x10,000)
Green 5 (x100,000) 0.5%
Blue 6 (x1,000,000) 0.25%
Violet 7 (x10,000,000) 0.1%
Grey 8 (x100,000,000) 0.05%
White 9 (x1,000,000,000)
Gold (x0.1) 5%
Silver (x0.01) 10%
No color 20%
So if you have a resistor that has Gold, a gap, green, brown, black, then you have it backward. Turn it the other way. It will always be read color, color, color, gap, color.
Now it is black, brown, green, gap, gold. That means 1, 0, (x100,000), 5%. Take the 1 and 0 (making 10) and multiply by 100.000. That's 1,000,000, or 1 mega-ohm. Take the tolerance band of 5% and add and subtract the number (50,000) from 1,000,000. This gives you the range of the resistor between 1.05 Mega-ohm and 0.95 Mega ohm.
So in a perfect world, this resistor would be exactly 1 MOhm, but the tolerance band tells us that it should be between 1.05 MOhm and 0.95MOhm.
There are various ways, according to the physical size of the resistor. For small resistors, the most common method is by a series of coloured rings applied towards one end of the resistor. Larger resistors used to use a colour code system called the 'body-tip-spot' method, but this is now obsolete. Large, wire-wound, resistors, may have their resistance values printed on them using an alpha-numeric code, such as 7K5 -meaning 7.5 kilohms.
measure the voltage drop divided by the resistance.
No, a resistor isn't measured at all. A resistor has a quality called "resistance" - and that value is measured. Resistance is measured in Ohms.
That will depend on the specific design needs.
Ix = IT(Rp/Rx+Rp) where Ix is the current you are trying to find, IT is the total current, Rx is the resistor in question, Rp is/are the resistor(s) in parallel with the resistor in question.
as we can deduce from its name, the resistor "resists" to the current (the movement of the electrons) so as the value of the resistor increases, the current flowing through it decreases. so when you use a smaller resistor, the current increases, however the tension between its poles decreases ( due to the voltage divider law). remember that the shortcircuit is due to the small value of the current , so we need always to have a resonable resistance on the circuit..... but not too high because joule losses we'll be more significant !! hope i've been clear :D
The purpose of colored bands on a resistor is to tell whoever is installing the resistor the amount of resistance that particuliar resistor has.
Resistor value is defined by the Resistance the resistor offers in Kilo ohms/ohms value given by color codes on the resistor.
Variable resistor. The value of the variable resistor can be changed at any given moment.
No, because the power dissipated in a resistor is proportional to the square of the current through the resistor but only directly proportional to the resistance of the resistor (I^2 * R) and the current through the lower value resistor will be higher than the current through the higher value resistor, the lower value resistor will usually dissipate more power.
just to find out our given unknown resistance value or to put it another way, To find the value of the unknown resistor attached.
There is no relation between the resistor's ohms value and its size. The power of the resistor can be seen by its size. If the power is too small, the resistor can be destroyed.
Where would you find a material which is a resistor? You can find a resistor material in Europe
A: If you know the total resistance and total voltage then you know total current flow for the circuit, this current will be same for every resistor in series however the voltage drop will change for each resistor . So measuring the voltage drop across the resistor in question and divide by the total current will give you the resistor value.
The first 3 band on a resistor indicate the value of that resistor.
find a sheet with all the colour values on it :) This sheet can be found on related link down below.
if not disconnected you will measure the resistance of the circuit in parallel with the resistor.
It's a code to tell you the value of the resistance of the resistor.
if you want to find the current (in amperes) through the resistor then connect a ammeter in series with the resistor.