In this video, we’re going to be looking at the power resistors. Here they are on the left-hand side, and as you can see, there are six of them. Each of these are rated for 50 watts of power. However, this excludes the 39O resistor, which is only rated for 25 watts. Since these resistors have such high wattage, they are intended to be used in higher current circuits. But also keep in mind that they can get extremely hot. The maximum voltage that can be applied to each one can be calculated by using the power formula.

We’ll first do one example with the 2-ohm resistor. If we start off with our equation of power, which is equal to voltage square divided by resistance, and then we rearrange the equation to find voltage, we can determine the maximum voltage by plugging in our known values of resistance and power, which are 2-ohms and 50 watts respectively. This ends up giving us 10 volts. The same process can be done for each resistor, which results in values as shown in the table. But also keep in mind that the maximum voltage of the supply is 25 volts.

To demonstrate the operation of the power resistors, we’re going to connect one directly across the supply. We’ll use the 20-ohm resistor as an example. First, I’m going to set the supply to 20 volts. Then I’ll connect my laser between the supply and across the resistor terminals. I’ll also connect the multimeter across the resistor to monitor the voltage drop across it. When I turn the supply on, you can see that the actual voltage of 19.8 volts is slightly less than the set voltage of 20 volts. This deviation is a common characteristic affected by the limitation of most power suppliers.

As we continue powering the resistor, you’ll also notice that it begins to get warm and eventually hot. We can use this thermometer to measure the temperature of the resistor. As you can see, the 20-ohm resistor is currently 73 degrees, whereas the 20-ohm resistor just below it, which hasn’t been powered, is 24 degrees. The power resistors can get very hot in high current circuits, so please be careful when touching them. Also, remember to not exceed their rated power. And be sure not to leave these resistors powered for more than two minutes.

That’s all for now. If you have any questions or feedback in regards to this video, please don’t hesitate to email or call using the phone number shown on screen. If you want to know more about the other components, please feel free to see our other videos. And as always, thanks for watching.