Electrical

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# Resistor Problems

An electrical device that reduces the amount of power running through a circuit is known as a resistor. It can be made up of different kinds of materials like metal-film, carbon or wire. When resistors get damaged, depending on what they are constructed out of, they can give rise to several electrical problems that can stop a circuit from working properly. Any resistor that has short-circuited or has a manufacturing defect must be replaced immediately.

Listed below are a few questions answered by the experts on problems related to resistors.

## What kind of resistor has orange, white, black and gold stripes? And how do I know how many watts I would need?

A 39 ohms, +/-5% resistor is probably what you are looking for and you should be able to pick it up from a local electrical supply house or a Radio Shack. To determine the wattage you need, you can either get in touch with the manufacturer and check the input voltage to the resistor, or refer an engineering spec sheet. Thereafter, feed electricity to the board and determine the voltage from the reading that you take at the resistor location.

## When you have two resistors with different resistances connected in a series, what happens to the voltage and current of the two components?

The drop in voltage across each resistor will depend on its resistance and the voltage that is coming from the source. Therefore, the voltage would be different for both components but the current will remain the same.

## I am in the process of adding an indicator LED to a 30 volt system. What kind of resistor do I require to reduce 30 volts to 12 volts @1 watt?

Case details: Voltage – ac from solar control leg, power draw on the light – less than 1 watt, single 12 volt LED, light specs - supply 12 volt type-16 volt max / current 12 mA type - 20 mA max

The resistor you will probably need is a 1/2W or greater 1500 ohm one. Brown green red is the usual color code for this kind of resistor.

## On an addressable fire alarm system, what is the end of line resistor used for?

It is used to monitor the system and give it standard resistance to determine whether there is a short or break. Depending on what make you choose, it can vary from 4.7 K to 47K.

## To power blue LED dimmable rope lights, I connected a residential dimmer switch to a remote dimmer outlet. Everything seemed ok till I turned the dimmer switch off and found that the lights continued to glow dimly. Other dimmers I have tested also seem to have this problem when switched off. I am now looking for a resistor to help. Can you tell me how to fix this?

One way you could solve this problem is to look for a new dimmer that is designed to handle magnetic loads. They are a little expensive but since your circuit is magnetic, they should work well. Alternatively, you could look at a biasing resistor. Finally, if you decide not to go with any of the above, you can use a normal two pole switch for hot and neutral before the dimmer to prevent the current from flowing after you switch it off.

A common problem that many resistors face is the danger of burning out. A resistor burns out for the same reasons that electrical light bulbs do. It could be because the resistor has encountered high voltage, there is too much electricity flowing through it or simply because it has overheated. A resistor is usually rated for the amount of power it can dissipate and its resistance is measured in ohms. As long as it does not dissipate more power than what it has been designed for, a resistor should last for a long time. However, if it burns out, it should be replaced without delay.

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