Power Dissipation in Resistance

Tue Aug 14, 2018 1:19 pm

Any resistor in a circuit that has a voltage drop across it dissipates electrical power. This electrical power is converted into heat energy hence all resistors have a power rating. This is the maximum power that can be dissipated from the resistor without it burning out.
When current flows in a resistance, heat is produced because friction between the moving free electrons and the atoms obstruct the path of electron flow. The heat is evidence that power is used in producing current. This is how the fuse opens, as heat resulting from excessive current melts the metal link in the fuse. Power Dissipation in Resistance Resist10

Power Dissipation in Resistance Resist10

Since power is dissipated in the resistance of a circuit, it is convenient to express the power in terms of the resistance R. The formula P = V x I can be arranged as follow: substituting IR for V,
P = V x I
P = (IR) x I
P = I²R

For another form, substitute V/R for I. Then
P = V x I
P = V x V/R
P = V²/R

Any of the three formulas can be used to calculate the power dissipated in a resistance. The one to be used is a matter of convenience, depending on which factors are known.

Lets take a look at the example.
Power Dissipation in Resistance Circui10

Power Dissipation in Resistance Circui10

Here, we have a single 9 V battery, and a single 100 ? (100 Ohm) resistor, hooked up with wires to form a complete circuit.
To find answer, we need to be able to calculate the amount of power that the resistor will dissipate.
Here’s the general rule for calculating power dissipation:
Power Rule: P = I × V
If a current I flows through through a given element in your circuit, losing voltage V in the process, then the power dissipated by that circuit element is the product of that current and voltage: P = I × V.

Aside:
How can current times voltage end up giving us a “power” measurement?

To understand this, we need to remember what current and voltage physically represent.

Electric current is the rate of flow of electric charge through the circuit, normally expressed in amperes, where 1 ampere = 1 coulomb per second. (The coulomb is the SI unit of electric charge.)

Voltage, or more formally, electric potential, is the potential energy per unit of electric charge —across the circuit element in question. In most cases, you can think of this as the the amount of energy that is “used up” in the element, per unit of charge that passes through. Electric potential is normally measured in volts, where 1 volt = 1 joule per coulomb. (The joule is the SI unit of energy.)

So, if we take a current times a voltage, that gives us the amount of energy that is “used up” in the element, per unit of charge, times the number of those units of charge passing through the element per second:

1 ampere × 1 volt =
1 ( coulomb / second ) × 1 ( joule / coulomb ) =
1 joule / second

The resulting quantity is in units of one joule per second: a rate of flow of energy, better known as power. The SI unit of power is the watt, where 1 watt = 1 joule per second.

Finally then, we have

1 ampere × 1 volt = 1 watt

Thu Aug 16, 2018 12:42 pm

Admin, since you're talking about the Power Dissemination in Resistance, and it is related to Resistor, what are the different types of resistors?

Tue Sep 04, 2018 12:15 pm

paano ko magagamit ang mga mga formula na ito in real life situation ? hehe Very Happy

Tue Sep 04, 2018 12:16 pm

Katty wrote:Admin, since you're talking about the Power Dissemination in Resistance, and it is related to Resistor, what are the different types of resistors?

yung karaniwang alam ko na ginagamit ay Carbon Resistor Cool

Tue Sep 04, 2018 12:19 pm

out of the coverage ng topic mo, pero gusto ko lang itanong bakit kapag patay sindi ang ang fluorescent lamp madaling mapundi ?

Tue Sep 04, 2018 12:25 pm

mahalaga ba na iconsider din ang type ng resistor bukod sa value nito?

Tue Sep 04, 2018 1:00 pm

niella wrote:mahalaga ba na iconsider din ang type ng resistor bukod sa value nito?

yes po, kaya nga may ibat ibang type ng resistor, it depends on what kind of circuit you are going to use it. There are a lot of different resistor types, all with their own applications

Read more http://www.resistorguide.com/types/ Wink

Tue Sep 04, 2018 1:19 pm

Katty wrote:Admin, since you're talking about the Power Dissemination in Resistance, and it is related to Resistor, what are the different types of resistors?

okay, since you are asking Smile

based on http://www.resistorguide.com/types/ we have fixed resistors like carbon film resistor, small common type of resistor we usually know, next one is the variable resistor, means that the value is adjustable, the thermistors which the resistance changes significantly when temperature changes, varistor and many more.

Wed Sep 05, 2018 2:42 pm

niella wrote:

Katty wrote:Admin, since you're talking about the Power Dissemination in Resistance, and it is related to Resistor, what are the different types of resistors?

yung karaniwang alam ko na ginagamit ay Carbon Resistor

There are two basic types of resistors.
Linear Resistors
Non Linear Resistors

Wed Sep 05, 2018 2:44 pm

How does the value of resistor affect the power of the circuits?

Wed Sep 05, 2018 2:44 pm

niella wrote:out of the coverage ng topic mo, pero gusto ko lang itanong bakit kapag patay sindi ang ang fluorescent lamp madaling mapundi ?

Hndi. Pero panigurado nakakapagod yun para sa kanya. Sa isang relasyong kapag on and off nakakapagod diba?? Ayyy jokeee Laughing

Pero sa tingin ko oo, isang factor ding ng mabilis na pagkapundi yung patay sindi, kasi yung sa voltage diba, once na binuksan mo yung ilaw dun nag sstart yung pag push ng voltage sa current. Kaya ayun, sa palagay ko lang naman Very Happy

Wed Sep 05, 2018 2:46 pm

Pareho lang ba ang Power at Current? Very Happy

Wed Sep 05, 2018 2:47 pm

DRAVEN wrote:

niella wrote:out of the coverage ng topic mo, pero gusto ko lang itanong bakit kapag patay sindi ang ang fluorescent lamp madaling mapundi ?

Hndi. Pero panigurado nakakapagod yun para sa kanya. Sa isang relasyong kapag on and off nakakapagod diba??

Wed Sep 05, 2018 2:49 pm

Meron bang other way to memorize the formulas of power?
diba kase meron sa Ohm's law yung Circle diagram.

Wed Sep 05, 2018 4:39 pm

paano maapektuhan ng current yung power na nag flo flow sa isang circuit?

Wed Sep 05, 2018 4:42 pm

Hello, please show us examples on applying the formulas.

Wed Sep 05, 2018 4:46 pm

DRAVEN wrote:

niella wrote:out of the coverage ng topic mo, pero gusto ko lang itanong bakit kapag patay sindi ang ang fluorescent lamp madaling mapundi ?

Hndi. Pero panigurado nakakapagod yun para sa kanya. Sa isang relasyong kapag on and off nakakapagod diba?? Ayyy jokeee

Pero sa tingin ko oo, isang factor ding ng mabilis na pagkapundi yung patay sindi, kasi yung sa voltage diba, once na binuksan mo yung ilaw dun nag sstart yung pag push ng voltage sa current. Kaya ayun, sa palagay ko lang naman

according din kase sa IEEE Xplore baka daw cause siya ng short fall of electricity.

Wed Sep 05, 2018 4:50 pm

niella wrote:mahalaga ba na iconsider din ang type ng resistor bukod sa value nito?

Yes po kase ung ibat ibang type of resistor ay may ibat ibang wattage rating, When resistors with higher wattage ratings are required, wirewound resistors are generally used to dissipate the excessive heat.

Wed Sep 05, 2018 4:51 pm

May power dissipation din ba sa transistors? Smile

Wed Sep 05, 2018 4:54 pm

Is it Super important na ifollow yung rules of Power? Very Happy

Thu Sep 06, 2018 12:35 pm

Does power dissipated increase with resistance?

Thu Sep 06, 2018 12:35 pm

Does more resistance mean more power?

Thu Sep 06, 2018 12:36 pm

kookie wrote:May power dissipation din ba sa transistors?

Power is the voltage across something times the current going through it. Since the small amount of current going into the base is irrelevant in power dissipation, calculate the C-E voltage and the collector current. The power dissipated by the transistor will be the product of those two.

Thu Sep 06, 2018 12:38 pm

kookie wrote:Pareho lang ba ang Power at Current?

Electric current is the actual rate of flow of electrons past a given point, in a unit of time, while power, measured in Watts, is the amount of work electricity can do in a circuit. Watts are calculated by the Voltage times Amps in a circuit.

Thu Sep 06, 2018 12:41 pm

niella wrote:Hello, please show us examples on applying the formulas.

Example
Calculate the power dissipated in a 10k resistor with a 5mA current through the resistor.

p= i² x R
p = (5*10-3)2 * 10 * 103
p = 250mW.
The power dissipated in the resistor is 250mW.

Power Dissipation in Resistance

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