Resistor Power Rating: What Does It Mean?

In summary, resistors are typically described by their resistance, measured in ohms. However, some resistors also have a power value listed, such as 40 watts. This power value is not solely determined by the voltage of the power source, as it also depends on the current passing through the resistor. Different resistor types are designed to handle different levels of power, and the power value listed may be a current limiting rating.
  • #1
quantum13
66
0
i have a question about resistors. i thought they were described by their resistance - 20 ohm, 40 ohm, 2 Megaohm, etc.

how come I see "power" values on resistors? for example my lightbulb says 40 watts. but i thought the power is simply P = V^2/R and that would depend the voltage of my power outlet whatever that happens to be. The power would only be partially determined by the lightbulb. so what does it mean to see a power value on a resistor?
 
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  • #2
Q, If you put too much current through your resistor it will get too hot. There are different resistor types intended for different degrees of power they need to dissipate. Maybe P=I^2 * R, so it's a current limiting rating.
 

1. What is a resistor power rating?

A resistor power rating is the maximum amount of power that a resistor can safely dissipate without overheating or being damaged. It is typically measured in watts (W) and is an important factor to consider when selecting a resistor for a circuit.

2. How is resistor power rating determined?

Resistor power rating is determined by the physical size and materials used to make the resistor. The larger the resistor, the higher its power rating will be. Additionally, resistors made from materials with higher heat resistance, such as metal film or wirewound, will have a higher power rating compared to those made from carbon composition or carbon film.

3. Why is it important to consider resistor power rating?

It is important to consider resistor power rating because exceeding the maximum power rating can cause the resistor to overheat and potentially fail, leading to circuit malfunctions or even fires. It is also important to ensure the power rating is sufficient for the intended application to avoid any unexpected failures.

4. How does resistor power rating affect the circuit?

The power rating of a resistor affects the circuit by determining how much power the resistor can safely handle. If the power rating is too low, the resistor may overheat and fail, causing the circuit to malfunction. On the other hand, if the power rating is too high, the resistor may not provide the necessary resistance and could cause other components in the circuit to fail.

5. Can a resistor's power rating be increased?

No, a resistor's power rating cannot be increased. The power rating is determined by the physical characteristics and materials of the resistor and cannot be changed. It is important to select a resistor with a sufficient power rating for the intended application to avoid any potential issues.

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