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A: RATING is a term to describe the capabilities of any components active or passive to perform as designed. Power of a resistor must be rated to safely dissipate within its own power rating
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What physical characteristic determines the power rating of a resistor?
The size of a resistor is a physical characteristic that determines its power rating.
Can you measure the physical size of a resistor to determine its wattage?
there might be ways to get the power rating by measuring the size of the resistor. but as the physical size of the resistor increases, its power rating also increases..
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).
What is maximum power rating?
Maximum power rating describes the maximum power at which a device can operate without reaching an excessive temperature. For example, in the case of a resistor, if its maximum power rating is exceeded, then it may burn out.
What is the current through the 150 ohm resistor?
It depends on the voltage applied across it. But the maximum current is limited by the power-rating of the resistor (power divided by the square of the voltage).
At what level will typical resistors burn out?
A typical resistor will burn out when it dissipates power in excess of double its power dissipation rating for an extended period of time. The power dissipated by a resistor is equal to I2R or E2/R, where E = the voltage across the resistor I = the current through the resistor R = the resistance of the resistor
How does the Resistance and Wattage relate to maximum voltage of a wirewound resistor?
The power rating of a resistor is determined by its physical size. The greater its surface area, the better it can dissipate energy, so the higher its power rating. Knowing its power rating and its resistance will determine the maximum voltage that can be applied to it in order to ensure the resulting current doesn't cause the resistor to overheat. This can be determined by manipulating the equation, P = U2/R.
What does 1 4W and 1 8W means for resistors and do they affect the value of the resistor?
It means the maximum power each one is capable of dissipating. The power dissipated by a resistor is (current through it)2 x (its resistance). If you exceed the power rating of a resistor, it will overheat, and that always increases its resistace value, at least for as long as it remains hot. If you take it to the extreme, the resistor can melt, smoke, crack, explode, etc. The power rating of a resistor has no direct effect on its resistance value.
What is equivalent wattage when different wattage resistors are connected in parallel?
In order to determine this, it will be necessary to find which resistor 'maxes out' at the lowest voltage. This can be found using the equation Vi=sqrt (Pi*Ri) for each resistor, where Pi is the power rating of resistor i and Ri is the value of resistor i. Once this is found, the power dissipation of each other resistor can be found using the equation Pi=(Vl^2)/Ri, where Vl is the voltage that maxes out the resistor which maxes out at the lowest voltage, and Ri is the resistance of each resistor. The equivalent power rating would then be the sum of the power dissipated across each resistor.
How are current ratings given to a resistor?
Resistors are not usually given 'current ratings' but, rather, 'power ratings' expressed in submultiples of the watt. It is then up to the user to calculate the safe maximum operating current for a particular resistor, by manipulating the equation: P = I2 R.Since a power rating is dependent upon the resistor's ability to dissipate energy by heat transfer, the actual power rating is dependent upon the surface area and, hence, the physical size of the resistor. So you will find that resistors come in a variety of physical sizes for any given resistance value.Unfortunately, power ratings are not indicated through colour codes, etc., so you will have to either specify its power rating when you purchase a resistor, or match your existing resistor against a scale-drawing to determine its power rating.
What is the current flowing through a 200 watt resistor that has a rating of 21 ohms?
The current can't be calculated from the information given in the question.The power rating of a resistor is the maximum power it can dissipate before it overheatsand its resistance possibly changes permanently. The power rating is not the amount ofpower it always dissipates.So, all we really know about the resistor in the question is that its resistance is 21 ohms.And all we can say about the current through it is:Current through the resistor = (voltage between the ends of the resistor) divided by (21).
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.
