Continue to Site

# The difference between 1/4W and 1/2W resistors

Status
Not open for further replies.

#### distinct

##### Newbie level 4
When I wanted to order resistors from a website, I noticed they have 1/4W resistors and 1/2W resistors categories. what is the difference between them and which one fits more for electronics work?

Re: Resistors Confusion

That's their power rating. P=VI=I^2R which has the units W (Watts). Just pick one which satisfies your power needs, they'll both work just the same as each other (as resistors).

Re: Resistors Confusion

Hi My Friend
the diffrence between resistor is at ohm and power which is
R=V/I
P=I^2 x R = V^2/R = IxV

and note that the size of resistor is dependent on Power

thanks

Re: Resistors Confusion

distinct said:
When I wanted to order resistors from a website, I noticed they have 1/4W resistors and 1/2W resistors categories. what is the difference between them and which one fits more for electronics work?

Hi Distinct,

the value that you have read refers to the amount of power
that those resistors can handle at ambient temperature.

Regards

Re: Resistors Confusion

that's for power rating. analyze your cky first.

Resistors Confusion

It is required for the power disiipation. Find out how much current you are going to have through the Resistor and choose the rated resistor accordingly..

Re: Resistors Confusion

HI...
If you buy and 1kΩ 1/4 W resistor and next you work with it with more than 15 mA it will frying...

OK?

So if you'll work with more than this CURRENT with this value of resistor u must buy an 1/2 W .

Vincengineer

Re: Resistors Confusion

The important: the resistor will burn itself if the current (and consequently the power) passing through it is more than what it can handle/dissipate. It becomes very hot in this case, and sometimes it releases smoke, and changes its nominal value.
Also, check the size, format, terminal diameter as 1/2W resistor usually is larger than the 1/4W resistor. It always depend on your design.
For low power applications, 1/8W resistors are suitable for prototypes and short experiments in the breadboard.

Re: Resistors Confusion

hi
usually when you don't have a power problem like in your case ( i mean that it doesn't seem you're working in high power electronics) you don't need more than the 1/4 watts resistor.
anyways, check it's the same resistor except that the 1/2 watts can stand more current

Resistors Confusion

depend on your application, if your circuit is high power, y should use the high power resistor

Re: Resistors Confusion

the difference is that the 1/2 w resistor can stand more power ( current) that the other one. usually the 1/2w is greater in size. Acually, which one you should choose depend on you aplication, some need high current and others need less.

Re: Resistors Confusion

1/4W means - The maximum power dissapation should not exceed 250mW
1/2W means- The maximum power dissapation should not exceed 500mW

U have to calculate the current through the resistor according to ur resistor value and find the power dissipation. P = I * I * R. If ur P is < 250mW then use 1/4W and vice vera.

Hope it helps
-VJ

Resistors Confusion

DEAR FRIENDS
I TOO HAVE THE CONFUSION REGARDING THE RESISTOR WATTAGE SELECTION.
I HAVE A CIRCUIT WHICH CONSUMES 100mAPS AT 9V,IF I HAVE POWER SOURCE OF9V 1000mAPS .IF I CONNECT THE CIRCUIT WONT IT BURN IT.PLEASE ANY ONE GUIDE ME

Re: Resistors Confusion

Helo Snf280,
The current rating of a 9V supply specifies the maximum current power it can deliver. A circuit which takes 100 mA at 9V will take the same current even from a 9V,1000mA supply. For a given voltage, the power dissipated in the load does not depend on the capacity of the source. So by connecting a 9V, 1000mA supply will not damage a circuit operating at 9V, 100mA. From power dissipation point of view, it is better for the supply to run on lesser currents than its rating.
Regards,
Laktronics

Re: Resistors Confusion

1/4W and 1/2W ratings indicate the maximum power that the resistor is able to handle for temperatures lower than 70°C.

The power is to be intended as average power

Re: Resistors Confusion

1/4W resistors are most popular and cheapest. 1/2W is only used in the power circuits.

The dissipation power of a resistor P (W) = V (V, drop-out voltage on resistor) * I (A, current fed through the resistor)
or = V^2/R or = I^2*R. (resistance in ohm).

Check the suitable conditions for your resistors, note that the practical dissipation power Pprac. must be <= 1/2 rated dissipation power of the resistor itself.

Resistors Confusion

depend on your application,if the disspated power is high y need choose high power resistor

Re: Resistors Confusion

HELLO MR LAKTRONICS,
THANK YOU FOR CLEARNG MY DOUBT AND IT WORKED AS YOU SAID
REGARDS
SNF

Status
Not open for further replies.