Why does the resistance of a lamp change?

The resistance of a filament lamp increases as the potential difference increases because the filament becomes hot. The movement of electrons (which is what causes the current) makes the atoms inside the filament vibrate faster and this makes the filament heat up.

Why does resistance of a bulb change?

The resistance of a lamp increases as the temperature of its filament increases. The current flowing through a filament lamp is not directly proportional to the voltage across it.

What effect does resistance have on a lamp?

The higher the resistance, the lower the current. Resistance is caused by the charge-carrying electrons colliding with the atoms in the conductor and bouncing off in different directions. The current in a bulb affects its brightness. The higher the current, the brighter the bulb.

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What happens to the resistance in a lamp as the current increases?

As the potential difference across the filament lamp increases the current across the lamp also increases due to Ohm’s law. The increase in current flow also causes the lamp to heat up which causes the resistance of the lamp to also increase.

Is the resistance of a lamp constant?

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.

What is the effect of changing the voltage and resistance on the light bulb?

Each bulb has a maximum voltage potential that it can utilize or withstand from that design, but its resistance is fixed. When voltage is increased , according to P=VI power will increase. Consequently the bulb will glow brighter.

What factors might influence the resistance of the lamp filament?

There are 4 different factors which affect resistance:

  • The type of material of which the resistor is made.
  • The length of the resistor.
  • The thickness of the resistor.
  • The temperature of the conductor.

Why does the resistance of a filament lamp change with voltage?

The resistance of a filament lamp increases as the potential difference increases because the filament becomes hot. The movement of electrons (which is what causes the current) makes the atoms inside the filament vibrate faster and this makes the filament heat up.

How does resistance change in a diode?

The diode has 2 key resistance change periods, at the breakdown voltage and at the threshold voltage. Resistance does not change much but after the diode reaches the threshold voltage, resistance just decreases drastically, allowing a great amount of current to rapidly pass through the diode.

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How does resistance change with potential difference?

Evaluation. For a fixed resistor, the potential difference is directly proportional to the current. … This relationship is called Ohm’s Law and is true because the resistance of the resistor is fixed and does not change.

Does resistance increase with current filament lamp?

Yes. To the extent that filament resistance increases with temperature. As the lamp heats up, the resistance increases, which reduces the current, and thereby reducing the resistance.

Why does resistance increase with temperature?

As electrons move through a metal conductor, some collide with atoms, other electrons or impurities. These collisions cause resistance and generate heat. Heating the metal conductor causes atoms to vibrate more, which in turn makes it more difficult for the electrons to flow, increasing resistance.

Why does the bulb of the filament lamp gradually darken over time?

Over time, the filament slowly boils off energetic atoms of tungsten. When they reach the cold glass envelope, they condense just like dew forming on a cold car window. Since the glass is getting coated with a metallic layer, the glass becomes darkened.

Why does a filament lamp not obey Ohm’s law?

The filament lamp does not follow Ohm’s Law. Its resistance increases as the temperature of its filament increases. So the current flowing through a filament lamp is not directly proportional to the voltage across it.

Why might the filament inside a lamp melt when the lamp is first switched on?

When switched on at first the bulb filament is cold. It therefore has a low temperature. … Otherwise that current surge could reach values of current that will produce enough heat energy to melt the filament wire.

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What is the resistance of a light bulb?

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.