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What size resistor is required for 40 watts in a 120 volt circuit?
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What does the physical size of a colour-coded resistor indicate?
the physical size tells how much power it can dissipate (watts)
How do you size a generator to operate a pump that draws 7 amps on each leg of a 240 Volt Circuit?
At 240 volts, and 7 amp current, you will have a load of 1680 watts (volts x amps = watts). A 2000 watt generator will sufice, however a 3500 watt generator, if within your budget, will power a few other necessities if required.
What is the minnimum size equipment grounding conductor required by the NEC for a branch-circuit protected by a 50-ampere rated circuit breaker?
#10 copper
600 watts requires how many amps?
It depends on the voltage source. watts = voltage * voltage / resistance and amps = voltage / resistance example 1: To produce 600W from a 120V source, you need a resistor of size 120V*120V/600W = 24 Ohm. This would pull 120V/24 Ohm = 5 amps. example 2: To produce 600W from a 240V source, you need a resistor of size 240V*240V/600W = 96 Ohm. This would pull 240V/96 Ohm = 2.5 amps.
How many baseboard heaters can you put on a 2 pole 15 amp breaker?
The question depends entirely on the size of the heaters and the size of the wire used.Select your breaker size and wire gauge according to the wattage. To determine your amperage, divide your power in watts by your voltage. If the voltage is 100 volts and your wattage is 1000 watts, then the amperage draw = 1000 Watts / 100 volts = 10 ampsIf you intend to control a number of heaters, a relay may also be used. The thermostat turns on the relay, the relay controls the heaters. Thermostats are rated for current and voltage. Make sure you are also using a thermostat big enough for your circuit.
What does the physical size of a colour-coded resistor indicate?
the physical size tells how much power it can dissipate (watts)
What do you call a variable resistor that is set up to alter the size of the current in a circuit?
A thermister is a device that changes resistance depending on temperature. A photo resistor changes resistance based on light. Both of these could be used with an amplifying circuit to vary current flow.
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.
How many watt values are there for resisters?
Some of the more common values are 1/8, 1/4, 1/2, 1 and 2 watts. On PC boards the larger resisters are not placed adjacent to the board but connected into the board above the board using standoffs. This is to let air circulate around the resistor to carry away the heat generated by the resistor. The physical size of the resistor reflects the resistors ability to dissipate the heat which builds up inside the resistor. As the wattage goes up so does the physical size of the resistor. Resistors that dissipate very large amounts of power (watts) are usually wire-wound resistors. Wire-wound resistors can be as high as 100 watts.
What is the relation between the size of the resistor and its value?
There is no relation between the resistor's ohms value and its size. The power of the resistor can be seen by its size. If the power is too small, the resistor can be destroyed.
How do you measure current without an amp meter?
Depends on the current. Put a resistor in-line with the current, then measure the voltage across the resistor. V=RI. So, divide the measured voltage by resistor value. Be careful with the size of the resistor, as Power dissipated in a resistor is R*I^2 or V^2/2. So, a 1-Amp current into a 1 Ohm resistor will result in a 1Watt power dissipated in the resistor. If it's too small, it'll burn. Also, notice that if you do that, you haven't measured the current in the original circuit. You've measured the current when an extra resistor is installed in the original circuit, and that's different.
How do you size a generator to operate a pump that draws 7 amps on each leg of a 240 Volt Circuit?
At 240 volts, and 7 amp current, you will have a load of 1680 watts (volts x amps = watts). A 2000 watt generator will sufice, however a 3500 watt generator, if within your budget, will power a few other necessities if required.
What is the minnimum size equipment grounding conductor required by the NEC for a branch-circuit protected by a 50-ampere rated circuit breaker?
#10 copper
Can you measure the physical size of a resistor to determine its wattage?
there might be ways to get the power rating by measuring the size of the resistor. but as the physical size of the resistor increases, its power rating also increases..
Is the heat loss and current of a resistor affected by being in a parallel circuit or can you just calculate it the same as in series?
The heat generated by any particular resistor depends (at least electrically) solely on the power it dissipates. Power dissipation in a resistor is equal to current squared times resistance, and the current through the resistor is equal to the voltage across it divided by the resistance. If we take a 10 ohm resistor ('your resistor') and put it in a series circuit such that there is 10 volts across your resistor, the current through it will be 1 ampere (10/10=1). the power dissipated will be 10 watts (1^2 * 10=10). If we put your resistor in a parallel circuit that also puts 10 volts across it, then the current and power will be the same. Your resistor does not know or care where the voltage came from. From this point of view, once you get down to the voltage across the resistor, it does not matter what type of circuit it is in. On the other hand, for any given power supply voltage, then the type of circuit and the value of external components certainly does affect the terminal voltage and thus the current through as well as the power dissipated by the resistor. In a parallel circuit, the voltage across your resistor remains basically the same no matter what resistance you put in parallel with it (unless you overload the power supply or the power supply has high internal resistance). In this case, the voltage across the resistor is the same as the power supply, current is I=E/R, R being that resistor only, and power is P=I^2 * R. In a series circuit the current through the resistors is I=E/R, R being the total resistance (including the other resistor(s)). The power dissipation in your resistor will then be P=I^2 * R, I being the series current we just calculated, and R being your resistor only. Since the other resistors affect the current, and since the current is the same no matter where you measure in a series circuit, then the voltage across your resistor and thus the power dissipation will be affected. The voltage across your resistor will be E=I*R, I being the series current we just calculated, and R being your resistor only. So, while the calculation for power dissipated in a particular resistor does not change relative to what type of circuit it is in, the calculation to arrive at the voltage across the resistor and/or the current through it (which you will then need to calculate power) does. Keep in mind there are other mechanical parameters that influence the actual case temperature of the resistor. Physical size of the case, composition, and airflow velocity, if any, will alter the case-to-ambient thermal conductivity. Ambient temperature will also be a factor in the final temperature.
How do you determine a resistor's wattage?
The physical size of the resistor determines how much power(wattage), or heat can be dissipated. The larger the resistor the more power it can dissipate. Resistance is the opposition to current flow(electrons) and this opposition causes heat to be generated when current flows through it. The AMOUNT of Heat dissipated per unit of time is measured in watts. example if P=I X E (power formula) P=Power(watts) E=Voltage I=Current ohm's law-->E=I X R say you are using a 1/2 w 100 ohm resistor and you put 12VDC thru the resistor to ground. determine the current: I=E/R I=12V/100 ohms I=120 ma. Plug in value into ohms law formula. P=I X E P=.120 x 12 P=1.44 watts (resistor will be dissipating 1.44 watts at 12v with 120 milli amps flowing thru it. Resistors come in different wattage values( 1/8w, 1/4w, 1/2w, 1w etc) usually printed on them. So for this case you would need at least a 2 WATT resistor and still be safe and NOT BURN and destroy it to a crisp. If the resistance has not changed then your resistor passed the required safe amount of current. If the resistance has changed you may have burned the resistor with too much current and thus you have overpowered it. You can also use a wattmeter and measure the wattage as voltage and current is applied to the resistor at a given resistance.
What size of resistor is required to operate the LED from a 9V battery?
In order to determine what size of resistor is required to operate an LED from a 9V battery, first start by knowing the current and voltage required for the LED. That information is available in the LED's specifications. For discussion purposes, lets assume a typical LED at 2.5V and 50mW. The translates to a forward current of 20mA. Build a simple series circuit containing a 9V battery, a resistor of an as yet unknown value, and the LED. By Kirchoff's current law, the current in the LED is the same as the current in the resistor, which is also the same as the current in the battery. This is 20ma. By Kirchoff's voltage law, the voltage across the LED plus the voltage across the resistor equals the voltage across the battery. This is 6.5V. (9 - 2.5) By Ohm's law, resistance is voltage divided by current, so the resistor is 6.5 / 0.02, or 325 Ohms. The nearest standard value to that is 330 Ohms. Cross check the power through the resistor. Power is voltage times current, or 6.5V times 0.02A, or 0.13W. A half watt resistor is more than adequate for this job.
