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The power dissipated across a resistor, or any device for that matter, is watts, or voltage times current. If you don't know one of voltage or current, you can calculate it from Ohm's law: voltage equals resistance times current.

So; if you know voltage and current, power is voltage times current; if you know voltage and resistance, watts is voltage squared divided by resistance; and if you know current and resistance, watts is current squared times resistance.

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What is the relationship between Wattage and resistance of resistor?

There is no direct relationship.Power ('wattage') is a measure of the rate at which the resistor can dissipate energy; excessive power means that a resistor cannot dissipate energy fast enough to prevent its temperature becoming excessive -excessive enough to damage the resistor.As the rate at which a resistor can dissipate energy is determined by its physical size, a resistor's power rating(maximum continuous power it can handle without exceeding its rated temperature) depends on the physical size of the resistor.On the other hand, the resistance of a resistor is notaffected by its physical dimensions, as a resistor can be manufactured to any particular value of resistance for whatever physical size is necessary to achieve its rated power.If you know a resistor's rated power and its resistance, then you can calculate the maximum continuous current that resistor can handle without overheating (using the equation: power = current squared x resistance).


What is the relation between the size of the resistor and its value?

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.


Is the heat loss and current of a resistor affected by being in a parallel circuit or can you just calculate it the same as in series?

The heat generated by any particular resistor depends (at least electrically) solely on the power it dissipates. Power dissipation in a resistor is equal to current squared times resistance, and the current through the resistor is equal to the voltage across it divided by the resistance. If we take a 10 ohm resistor ('your resistor') and put it in a series circuit such that there is 10 volts across your resistor, the current through it will be 1 ampere (10/10=1). the power dissipated will be 10 watts (1^2 * 10=10). If we put your resistor in a parallel circuit that also puts 10 volts across it, then the current and power will be the same. Your resistor does not know or care where the voltage came from. From this point of view, once you get down to the voltage across the resistor, it does not matter what type of circuit it is in. On the other hand, for any given power supply voltage, then the type of circuit and the value of external components certainly does affect the terminal voltage and thus the current through as well as the power dissipated by the resistor. In a parallel circuit, the voltage across your resistor remains basically the same no matter what resistance you put in parallel with it (unless you overload the power supply or the power supply has high internal resistance). In this case, the voltage across the resistor is the same as the power supply, current is I=E/R, R being that resistor only, and power is P=I^2 * R. In a series circuit the current through the resistors is I=E/R, R being the total resistance (including the other resistor(s)). The power dissipation in your resistor will then be P=I^2 * R, I being the series current we just calculated, and R being your resistor only. Since the other resistors affect the current, and since the current is the same no matter where you measure in a series circuit, then the voltage across your resistor and thus the power dissipation will be affected. The voltage across your resistor will be E=I*R, I being the series current we just calculated, and R being your resistor only. So, while the calculation for power dissipated in a particular resistor does not change relative to what type of circuit it is in, the calculation to arrive at the voltage across the resistor and/or the current through it (which you will then need to calculate power) does. Keep in mind there are other mechanical parameters that influence the actual case temperature of the resistor. Physical size of the case, composition, and airflow velocity, if any, will alter the case-to-ambient thermal conductivity. Ambient temperature will also be a factor in the final temperature.

Related Questions

What are the 2 defects of a resistor?

Power loss


Which one of the following equations could be used to calculate the power absorbed by a resistor?

p=I*I*R ,P=V*V/R;where I is the current passing through the resistor, and V is the voltage across resistor, and R is the Resistance of the resistor,


Why iron loss cald constant power loss?

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What is the power rating of a resistor?

The power rating of a resistor determines how much power it can dissipate without being damaged. For example, a 1/4W resistor is designed to handle up to 1/4W continuously without being destroyed. When selecting a resistor to use in a circuit, use Ohm's law to calculate the power it will dissipate. For example, placing a 1kΩ resistor across a 12VDC signal will allow 12/1000 = 0.012A to flow thru the resistor. 0.012*12 = 0.144W will be dissipated. Thus, a 1/8W (0.125W) resistor would not be sufficient, and a 1/4W (0.25W) must be used.


What is the function of a cement resistor?

A cement resistor is typically used as a power resistor (a resistor whose power rating is greater than 1 W).


To reduce the voltage, I need to change the voltage of 5v to 4.5v, I use a 30 ohm resistor, how many watts of resistor should I use?

To calculate the power rating of a resistor required to drop the voltage from 5V to 4.5V using a 30 ohm resistor, we can use the formula: Power = Voltage Drop x Current The current flowing through the resistor can be calculated using Ohm's law: Current = Voltage Drop / Resistance Substituting the values we get: Current = (5V - 4.5V) / 30 ohms = 0.0167 A (rounded to four significant figures) Now we can calculate the power required: Power = (5V - 4.5V) x 0.0167 A = 0.00835 watts So a resistor with a power rating of at least 0.00835 watts (or 8.35 milliwatts) should be sufficient for this application. However, it is recommended to use a resistor with a slightly higher power rating to ensure that it can handle any temporary power surges or variations in current that may occur. A 0.25 watt resistor should be suitable for this purpose.


How do you find power generated in a resistor?

The power generated in a resistor is converted into heat. and that can be power which is converted into heat is the product of the voltage across the resistor and, current passing through the resistor. or the product of square of the current and the resistance offered by the resistor.


Can you calculate the resistance of a component using a meter and a resistor?

yes you can! you can use a multimeter and a resistor.


What are the basics of how flashlights work?

You need a conductor, power source and a resistor. You need a conductor, power source and a resistor. You need a conductor, power source and a resistor.


How do you calculate power loss in T5 fluorescent light?

To calculate power loss in a T5 fluorescent light, you first need to determine the input power, typically measured in watts (W), which can be found on the ballast or the fixture label. Power loss can be calculated using the formula: Power Loss (W) = Input Power (W) - Output Power (W). The output power can be estimated based on the light output and efficiency of the fixture. Additionally, consider factors such as ballast efficiency and any heat generated during operation, as these contribute to overall power loss.


How do you calculate the conductance of a resistor?

how calcualte conductivity


What is the relationship between Wattage and resistance of resistor?

There is no direct relationship.Power ('wattage') is a measure of the rate at which the resistor can dissipate energy; excessive power means that a resistor cannot dissipate energy fast enough to prevent its temperature becoming excessive -excessive enough to damage the resistor.As the rate at which a resistor can dissipate energy is determined by its physical size, a resistor's power rating(maximum continuous power it can handle without exceeding its rated temperature) depends on the physical size of the resistor.On the other hand, the resistance of a resistor is notaffected by its physical dimensions, as a resistor can be manufactured to any particular value of resistance for whatever physical size is necessary to achieve its rated power.If you know a resistor's rated power and its resistance, then you can calculate the maximum continuous current that resistor can handle without overheating (using the equation: power = current squared x resistance).