What is the benefit of 1 ohm resistance in some electronic circuits?

[samy555]

Sometimes those small resistors have a high wattage and sometimes low.

thanks

 

[tpetar]

Sometimes those small resistors have a high wattage and sometimes low.

thanks

What is question?

Resistor make some resistance in circuit. Resistor power rating must follow expectations from resistor in circuit, according to current and resistance. P = I² x R

Metal film resistors are often smaller and have higher power ratings then carbon type resistors.

;-)

 

[samy555]

I know that .............
but why sometimes I found only one ohm or 0.5 ohm
i know that resistors limit currents
and two or more resistors make voltage divider etc
My question is why it is so small, why not using simply a wire
example; in many battery charger you may found some one ohm resistor just before the +ve pole of the batt.

thanks

 

[tpetar]

I know that .............
but why sometimes I found only one ohm or 0.5 ohm
i know that resistors limit currents
and two or more resistors make voltage divider etc
My question is why it is so small, why not using simply a wire
example; in many battery charger you may found some one ohm resistor just before the +ve pole of the batt.

thanks

See this example:

Resistor value of 0,1Ω used as current shunt. Its small resistance, used to make small voltage decline, and according to current rating through circuit. If you want to make current shunt of 0,1Ω copper wire, assuming copper specific resistance per 1m length, you will need long wire to make that resistance.

On other hand, we often use factory maded resistors, they have their declared ratings in declared tolerance.

- - - Updated - - -

in many battery charger you may found some one ohm resistor just before the +ve pole of the batt.

Its hard to tell without circuit, I supose this resistor is to lower charging current.

Also in lots of cars there is power low resistance resistor to limit current when battery is baddly discharged (lead acid). There is difference in current which battery will pull from power source when battery is almost empty and when battery is moderately discharged.

 

[samy555]

Thank you tpetar
English is not my first language,, so what did you mean by (shunt)
is it mean parallel?

 

[tpetar]

Thank you tpetar
English is not my first language,, so what did you mean by (shunt)
is it mean parallel?

The resistive shunt is a calibrated resistor placed in a current path that produces a voltage drop proportional to the current flow.



Materials for reading:

http://en.wikipedia.org/wiki/Shunt_(electrical)
**broken link removed**
**broken link removed**

;-)

 

[samy555]

Thank you again Mr. tpetar
From Wikipedia:
In electronics, a shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path.,,,,, thats enough,, I understand

 

[tpetar]

Shunts often have small resistive values such as 0,05-0,1-0,22R for higher values its standard resistors.

Your resistor of 1R is called resistor, and not shunt.

 

[ebclr]

The most comum use off 1 Ohm resistors, is to work as a current sensor, If the current is high the voltage across the resistor will go up, This voltage can inform a feed back circuit to decrease power or even turn off the circuit, Other typical use is mantain inrush current at aceptable levels.

 

[tpetar]

1R is to high for current sensing of course can be used for that, but I didnt saw 1R shunt for now, maybe someone use that high value. Usually current shunt is low to avoid influence on circuit in voltage and current.

 

[ebclr]

The advatange off use 1 R instead off 0.01 r for example. is that the generated tension will be a higher and the controling circuit with a higher tension will be more simple and less sucptible to noise, off course 1R will take more power than 0,01 R,

 

[vimalkhanna]

In snubbers circuits ,this is for the surge /charge power dissipation ,for current measurements it is acting as shunt for hi sensitivity DAM, in SMPS it is current sense limit stabilization,in class A amplifiers ,it is for matching the complementary stage Hfe,and in filters ,it can be for burst limit controls.
All depends on the applications of the resistance .