Frequent question: Does a light bulb have a constant resistance?

How much resistance does a light bulb have?

The filament of a light bulb is an extremely thin wire. This thin wire resists the flow of electrons. You can calculate the resistance of the wire with the resistance equation. So the resistance is 120 ohms.

Do light bulbs obey Ohm’s law?

An example of this is the filament light bulb, in which the temperature rises as the current is increased. Here, Ohm’s law cannot be applied. If the temperature is kept constant for the filament, using small currents, then the bulb is ohmic.

Why do light bulbs have resistance?

On an atomic scale, the moving electrons in the current collide with all the fixed atoms in the circuit which causes these atoms to vibrate more. The filament is just a very thin wire of high resistance and the vibrations due to the collisions with the moving electrons cause it to become hot and emit light.

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Is a bulb a resistance?

The typical cold resistance of a 100 W incandescent lamp is about 9.5 ohms. If that resistance stayed the same with 120 V applied, Ohm’s Law tells us that the bulb would draw about 12.5 amps and dissipate about 1,500 watts. … It turns out that at 120 V, the resistance is about 144 ohms, 15 times the cold resistance.

How do you find the resistance of a light bulb?

Since it involves the relationship of power voltage, current, and resistance, using the formula I=P/V with P and V known to find the current, and then using the formula R=P/I^2 to find the resistance will be the right steps to take.

Is a light bulb a conductor?

A light bulb is a device which produces light when electricity is passed through it. A bulb is made out of conductors as well as insulators. The filament, a thin tungsten wire in the light bulb, conducts electricity. Two wires that connect the supply to the mains are also conductors.

Why is the resistance of a light bulb non linear?

We could say that the resistance here is nonlinear, increasing with increasing current and voltage. The nonlinearity is caused by the effects of high temperature on the metal wire of the lamp filament. … At standard temperatures and pressures, air is an effective insulator.

Why does a light bulb not follow ohms law?

The filament in an incandescent bulb does not have a constant resistance. If you take a bulb and increase the voltage across it, the current increases too. An increase in current means the bulb gets hot—hot enough to glow. As the temperature increases, however, the resistance also increases.

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What is the difference between a resistor and a light bulb that makes it impossible to assign a resistance to a light bulb?

If you apply different voltages to a light bulb and measure the light bulb currents, you get different values of the ratio V/I. This makes it impossible to assign a resistance R to a light bulb. Things which do have resistance always yield the same V/I ratio no matter what voltage you apply to it.

Can the light bulb be accurately modeled as only a resistor?

LEDs do not have a linear relationship between current and voltage so they cannot be modeled as simply as a resistor using Ohm’s Law, V = IR .

What is the resistance of a light bulb if a potential difference of 120v will produce a current of 0.5 a in the bulb?

In fact, the 120-Watt bulb would have a current of 1 Amp and a resistance of 120 Ω; the 60-Watt bulb would have a current of 0.5 Amp and a resistance of 240 Ω.

How does the resistance of the light bulbs differ when the bulbs are cold and when the bulbs are hot?

when bulbs are cold their resistance is very low. this causes a large current to go through the bulb when first turned on. The large current can burn out the filament. When the bulb is hot, the resistance goes up and the current decreases.

Is a light bulb with more resistance brighter?

An incandescent bulb’s brightness depends on a whole lot on resistance. The higher the resistance to current in the wiring, circuitry, and bulb, the lower will be the current, lower the power, and lower the brightness. Conversely, lower resistance means more brightness.

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