A resistor is used in a circuit when the designer determines that the electrical property of resistance is requiredsomewhere in the circuit for it to operate. Its as simple as that. However selecting the correct value of the resistor as well as its wattage, tolerance, etc. is far less simple and must take into account values and types of many other components in the circuit.
1/2 watt (In theory you could use a "0.27 Watt" resistor, however there would be no safety factory and there is no standard value resistor that size.)
You need to use the 250 Ohm resistor in series with HART protocol communication because it acts as a shunt resistor.
The current would be about 20 volts.
possibly use a potentiometre
Since the current in a resistor is the same as the current in the leads/wires on either side of the resister, I might use a clamp meter such as an Amprobe to measure current, if the current was alternating (AC). Otherwise, I would have to break one of the leads and insert an ammeter or a multimeter with an amp setting into the circuit. Afterwards the broken connection would have to be repaired.
If your batteries were in series the total voltage would be 6 volts, and it the bulbs were in series you would need a resistor to keep them from burning out. In order to know how many ohms the resistor would need to be you would have to know the wattage of the bulbs, or the resistance of the bulbs. If you don't know the best thing to do is use a variable resistor. Then you can adjust it or the brightness that you want.
Where would you find a material which is a resistor? You can find a resistor material in Europe
Often we want to easily change a resistor value, so we use a variable resistor. For example, we may want to change the resistor that controls the power sent to a LED, so we can easily make it brighter or dimmer. Often if we use a variable resistor, there is only a very narrow range that is useful. Continuing our example, sometimes we use several LEDs, and we use the variable resistor to set them all to the same brightness. In this case, the resistance range that sets the LED to be twice as bright as the the other LEDs, and the resistance range that sends so much power to the LED that it is permanently destroyed is even less useful. So we add a fixed resistor in series with the variable resistor -- the fixed resistor sets the minimum net resistance, no matter how we turn the knob on the variable resistor. In our example, the addition of the fixed resistor allows us to turn the variable resistor throughout its whole range, and the LED gets brighter and dimmer; without that resistor, a certain range of the knob on the variable resistor would allow so much power to go to the LED that it would be destroyed.
It depends on where you are going to use this resistor and what its application going to be. If the circuit you are using can tolerate this then you are fine.
1/2 watt (In theory you could use a "0.27 Watt" resistor, however there would be no safety factory and there is no standard value resistor that size.)
You can only use a resistor to drop a voltage at a constant current. If you know the current, use Ohm's law to calculate the resistor value.
Because for each speed except the higgest one, to slow the motor of the fan, a resistor is choose and it's a big resistor, bigger to slow the speed and after long use or if the motor is defect (use to much currant), the resistor burn and no currant can pass trough
Basically you can either read the resistance that is printed on the resistor (with a special color code, which you would have to learn), or you can use Ohm's Law, by measuring a voltage through the resistor and the corresponding current. I am not aware of any third method.
I installed a resistor inline with my oil pressure sensor. The resistor in a circuit will usually disperse energy as heat.
You need to use the 250 Ohm resistor in series with HART protocol communication because it acts as a shunt resistor.
yes you can! you can use a multimeter and a resistor.
No, Using a resistor spark plug with resistor wires can create too much resistance for the ignition system.