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You will need to take the resistance of the load into account if you are going to design a voltage divider. The resistance of the load can completely change the voltage ratio of a voltage divider if not factored into the calculation.
you can measure or read R(load), then R(needed) = 0.8 R(load)
Wiki User
∙ 12y ago
Wiki User
∙ 11y agoIf you want a voltage drop of 2 volts across a resistor, then its resistance must be
( 2 ) divided by ( the current through the resistor, in amperes ) ohms
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Is it true that the higher a resistance value the higher the voltage drop?
Greater value resistor will absorb more voltage than smaller value. The more voltage absorb with same value current flow, the larger body mass resistor will require. Body size depends on type of resistor (material resistor is made of).
What size resistor is needed to drop 12 volt dc to 3 volt what is the formula?
The "size" (value or the power capacity) of the resistor can not be defined unless the power of the 3 volt bulb is known. If you tell me how many amps would the bulb draw from a 3 volt source, I will tell you exactly how many ohms of resistance, and how many watts of power capacity will be required of the resistor.
How do you switch the voltage requirement for a cooktop from 208 volts to 110volts?
You don't. The cook top was designed to operate on 208 volts. This is the voltage needed to get the elements up to their rated wattage to do the cooking. Higher wattage appliances do not operate on the lower voltage because of the size of the wire that is needed to feed the appliance.
When resistors are connected in series in a circuit. what are the relationships between the voltage drops across the resistor and the currents through the resistors?
When resistors are connected in series in a circuit . the voltage drop across each resistor will be equal to its resistance, as V=IR, V is direct proportional to R. An A: The relationship is that the current will divide for each paths in a parallel circuit and the voltage drop across each will be the source voltage. In a series circuit the current will remain the same for each component but the voltage will divide to reflect each different component value. And the sum of all of the voltage drops will add to the voltage source
What is the cable size of 110 KW motor?
The cable size depends on a few factors, such as the supply voltage, the method of starting the motor, (direct-on-line, or star delta) and the length of cable required to compensate for voltage drop. Also, if the cable is copper or aluminum.110 kW motor has a rated current of 200 amps at 415 volts, so the correct copper cable size would have a cross-sectional area of 75 square mm., if the motor is started direct-on-line.At 660 volts, the rated current would be 118 volts and the cable size would be 35 square mm.
What size resistor is needed to drop 14 volts dc to 12 volts dc?
This question cannot be answered because you did not specify the current.
What size resistor is needed to drop 24 volts dc to 12volts dc?
Its dependent what will by rated power of the device (current).
What is the volt drop across a 10k resistor with a 5 volt supply?
If there is nothing else in the circuit, then the voltage drop across the resistor will be the full supply voltage of 5 volts. The size of the resistor does not matter in this case - it will always be 5 volts.
What size resistor is needed to drop from 5vdc to 3vdc?
use Ohm's law: to drop 2 volts, V = I x R 2 = current x resistance resistance = 2 / current. So you need to know the current
What size resistor in parallel to reduce from 120 volts to 100 volts?
A resistor in parallel with a voltages source will not cause the voltage to drop, theoretically. To get a 20 volt drop you need a resistance in series, and the number of ohms is 20 divided by the current in amps. If the current is unknown or variable, the voltage can't be dropped by using a resistor.
How much ohms resistor is needed to drop 12 volts to 5 volts?
The size of the resistor will depend on the load. Let's look at this a bit to see if we can make sense of it. You want to drop the applied voltage to a device from 12 volts AC to 11 volts AC. That means you want to drop 1/12th of the applied voltage (which is 1 volt) across the resistor so that the remaining 11/12ths of the applied voltage (which is 11 volts) will appear across the load. The only way this is possible is if the resistor has 1/11th of the resistance of the load. Here's some simple math. If you have an 11 ohm load and a 1 ohm resistor in series, you'll have 12 ohms total resistance ('cause they add). If 12 volts is applied, the 1 ohm resistor will drop 1 volt, and the 11 ohm load will drop the other 11 volts. A ratio is set up here in this example, and each ohm of resistance will drop a volt (will "feel" a volt) across it. See how that works? If the resistance of the load is 22 ohms and the resistance of the (series) resistor is 2 ohms, each ohm of resistance will drop 1/2 volt, or, if you prefer, each 2 ohms of resistance will drop 1 volt. The same thing will result, and the load will drop 11 volts and the series resistance will drop 1 volt. That's the math, but that's the way things work. You'll need to know something about the load to select a series resistance to drop 1/12th of the applied voltage (which is 1 volt) so your load can have the 11 volts you want it to have. There is one more bit of news, and it isn't good. If your load is a "dynamic" one, that is, if its resistance changes (it uses more or less power over the time that it is "on"), then a simple series resistor won't allow you to provide a constant 11 volts to that load. What is happening is that the effective resistance of the load in changing over time, and your resistor can't "keep up" with the changes. (The resistor, in point of fact, can't change its resistance at all.) You've got your work cut out for you figuring this one out.
What size resistor is needed when wiring two leds in parallel using 6 volts dc?
A: LEDS are devices that needs a certain voltage and current typically 1.8 and 20 ma
What wire size is needed for 30amp load for 34 feet on 12 volts DC?
8 gauge will be sufficient with less than a half volt drop
What size resistor to change 12 volts to 3 volts for a led?
Assuming that you're talking about 12V DC you would use a 4 ohm resistor. If you mean AC then you would need a step-down transformer with a 4:1 ratio.
What size resistor is needed to allow a 220 volt coil in a relay operate on 277 volts?
You will need to know the amount of current flowing through the coil when 220 volts is applied across it. A resistor in series with the coil will limit the current so that the coil only sees 220 volts. The resistor will need to drop 57 volts. So, 57 volts divided by the current in amps will give you your required resistance. You will need a resistor with a high power dissipation rating with 57 volts across it. Your resistor will probaly need to dissipate several watts. For example: A 220 volt coil with 300 milliamps (.3 amps) will require a resistor of 733 ohms. The power dissipation of the resistor would need to be 17.1 Watts! You might try using a light bulb as a series resistor. Ensure that it can handle 57 volts. To complicate matters, is that AC or DC you are using? AC relays have inductance build in, in order to increase the specific "ac resistance", thus the same coil could use as little as 0,001A so you will need a very low value resistor. Anyway, if any 220V relay uses as much as 300mA, I doubt if you will be able to pick it up with one hand! Such a relay coil will draw about 66W of power! I have a 16A rated contact 230V relay. Its current is 0,0015A that is equivelant to 0.33W at 220V!
What size resistor to drop 9 dc to 3 dc at 1 amp?
330 milli ohms
What size ground wire needed for 75 amps at 208 volts?
#8 copper
