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What unit measures resistance to electrical current?
Unit measure for resistence is called as "OHM". Its law is called as "OHM'S LAW".
There is a current of 0.83 A through a light bulb in a 120 V circuit What is the resistance of this light bulb?
If a lightbulb has a resistance of 250 ohms, the voltage required for the bulb to draw a current of 0.5 A is 125 V. (Ohm's law: voltage equals current times resistance)Unfortunately, its more complicated than that...Is the resistance of 250 ohms the hot resistance or the cold resistance? It matters. It matters very much.Light bulbs have a dramatic positive resistance to temperature coefficient. It is not uncommon for the instantaneous on power to be 10 or 20 times the nominal value.So, if the 250 ohms is the measured resistance while operating at a current of 0.5 A, then 125 V is the correct answer. If the resistance is the cold resistance, you need to go back and find out the hot resistance at the desired operating point.
How hot does a filament light bulb get?
Hot, really hot. Typically in the range of about 2000C to 2500C (3600F - 4500F). It would be pretty difficult to directly measure the temperature of the filament so you have to use something other than a thermometer for the measurement. It should be possible to estimate the temperature of the filament from the light spectrum. Basically, treat the light bulb like a perfect black body radiator and use Plank's Law (http://en.wikipedia.org/wiki/Planck%27s_law) and the light spectrum of the bulb (for example http://www.graphics.cornell.edu/online/measurements/source-spectra/index.html) to calculate the temperature. Another way, which is a bit easier, is to use basic electronic theory to calculate the temperature of the filament that is required to produce the manufacturer's specifications for the bulb. For example, consider a typical 100 watt, 120 VAC light bulb with a tungsten filament. The bulb consumes (and radiates) 100 watts of power. A light bulb is a purely resistive load so Power=(Voltage)*(Current). Plugging in 100 watts as the power, 120 as the voltage (actually, that's the RMS voltage), and solving for current we get an RMS current of 0.83 amps. Since the bulb is just a resistor it obeys Ohm's Law; Voltage=(Current)*(Resistance). Our voltage is 120 and we determined the current to be 0.83 amps, so the resistance of the bulb when it is operating is 120/0.83= 144 ohms. If you take a 100W incandescent light bulb and measure its resistance at room temperature you get a value of about 15 Ohms. The difference between the room temperature resistance and the resistance when the bulb is operating is due to the affect of temperature on the filament's resistance. Metals (and conductors in general) increase their resistance as they are heated. The resistance at a particular temperature can be calculated with; R=Rref*(1 + alpha(T-Tref)] Where, R is the resistance at temperature T degrees Celsius. Rref is the resistance at a standard temperature Tref (often 0C or 20C). Alpha is the "temperature coefficient of resistance" for the material. For tungsten alpha=0.0044/C with a Tref of 20C (68F). If we assume that the 15 Ohm resistance at room temperature is close enough to the value at 20C (68F) then we can use Rref=15 ohms and R is the 144 ohms we calculated from the wattage and voltage of the bulb. Plugging these numbers into the equation; 144=15*(1 + 0.0044*(T - 20)) Solving for T (the temperature required to get the filament's resistance to 144 ohms) we get T=1975C (about 3600F). That's pretty hot! The filaments temperature will change if the applied voltage changes. The temperature will also be different from light bulb to light bulb (even if they have the same voltage and wattage ratings) since no two bulbs are exactly alike. An individual bulb will also change as it ages and as a function of the temperature outside the bulb.
If a circuit contains a 1.5 volts battery and a bulb with a resistance of 3 ohms. calculate the current?
Use Ohm's Law. Solving for current:I = V/R (current = voltage / resistance)
What are value of angle of incidence and angle of reflection for normal incidence of light on mirror?
Both are zero. Thereby it obeys the second law of reflection ie angle of incidence is equal to angle of reflection.
Is ohms law heat and light?
No.
What unit measures resistance to electrical current?
Unit measure for resistence is called as "OHM". Its law is called as "OHM'S LAW".
What difficulty will Aries while testing wheather the filament of light bulb obeys ohms law?
If you plot a graph of current against a range of voltages applied to an incandescent lamp, the result will be a curvedline. This tells us that the current is not proportional to the voltage and, so, the lamp does not obey Ohm's Law.However, the ratio of voltage to current will indicate the resistance for that particular ratio.
What voltage is required to sustain a current of 0.50 through a light bulb resistance of 190?
The voltage of a circuit with a resistance of 250 ohms and a current of 0.95 amps is 237.5 volts. Ohms's law: Voltage = Current times Resistance
How is the rating of a light bulb determined for instance 100W 60W is that how many watts an hour to run it?
No, the wattage is determined by the resistance of the filament in the light bulb. The formula to determine the wattage is Watts = Voltage (squared)/Resistance in Ohms. To find the resistance of a 120 volt light bulb use the formula, Resistance in Ohms = Voltage (squared)/Watts. So for a 100 watt bulb at 120 volts the resistance is 120 volts x 120 volts = 14400/100 = 144 ohms. For a 60 watt bulb at 120 volts the resistance is 120 volts x 120 volts = 14400/60 = 240 ohms. As you can see this holds true to Ohm's law, current is inversely proportional to the resistance of the circuit. The higher the resistance of a load, the harder it is for the current to flow. In this case less current results in less light being emitted from the filament in the light bulb.
What is the resistance of a lightbulb using Ohm's law?
By Ohm's law, resistance is voltage divided by current, so the resistance of a light bulb can be measured by observing the voltage across it simultaneously with observing the current through it. Interestingly, the hot resistance is significantly different that the cold resistance, so measuring resistance with an ohmmeter will not give a meaningful resistance. This is because the resistance of a light bulb has a positive temperature coefficient. Take a typical 60 W 120V light bulb, for instance... Its cold resistance is about 16 Ohms. Calculate current and power at 120 V and you get 7.5 A and 900 W. The truth is that at 60 W, the bulb pulls 0.5 A and has a resistance of 240 Ohms.
What happen if a 110 volt lamp connected on a low voltage?
If you had a 60 watt incandescent bulb it would draw about 1/2 amp. That means that the resistance of the bulb filament would be about 220 ohms. Now if you applied 12 volts DC across 220 ohms you would draw about .05 amps. This would not be enough to heat the filament and create any useful light. Remember Ohm's Law says Volts = Amps x Ohms.
How do you calculate 1.67 ohms?
ohms law.
What is the name of conductor which obeys ohm's law?
Everything obeys Ohm's law - antennas, cables, transformers, integrated circuits, etc.AnswerIt is not true that 'everything' obeys Ohm's Law. For a device to obey Ohm's Law, the ratio of voltage to current MUST remain constant for variations in voltage. This is why Ohm's Law is a law of constant proportionality.
When did James watt invent light bulb?
James Watt did not invent the light bulb. Thomas Edison is regarded by most people to have invented it. There were other similar ideas to the light bulb before Edison, however, it was his superior design and set up of entire electrical lighting systems that brought fame and popularity to his bulb. James Watt, is responsible for giving us the unit of measuring power that is his name (watt). The unit is derived by extending on Ohms law, to include that Voltage (e) times Amperage (i) = power.
What happens if you take away a load from a series circuit?
As an example imagine a 60 W light bulb running off 120 V. The current will be 1/2 A. Now assume that you put a second 60 W bulb in series with the first. Now the resistance of the single 60 W bulb is 240 Ohms. The 1/2 A flowing through the bulb heats up the filament wire and causes an amount of light to be emitted. Resistance in series adds, so the total resistance for two of the bulbs in series is 480 Ohms and by Ohms law V = I x R, the current through each bulb will be 1/4 amp and hence the bulbs will be less bright.
What state of mater obeys Boyle's law?
That Law applies to the Gas phase.
