# Why is the resistance of a lamp bigger when it is lit than when it is off?

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It contains a thin coil of wire called the filament. This heats up when an electric current passes through it, and produces light as a result. The resistance of a lamp increases as the temperature of its filament increases.

## Why does the resistance of the lamp increase as the potential difference across the lamp increases?

The more energy that is put into the bulb, the harder it is for the current to flow – the resistance of the bulb increases. As the potential difference increases, so does the temperature of the thin wire inside the bulb, the filament.

## How does the resistance change with the brightness of a lamp?

If the resistance remains the same increasing the voltage causes more current to flow heating the filament hotter making it brighter. Resistance plays a part too. The lower the resistance the higher the current flow and thus more heat and more light too. This creates a higher wattage lamp which produces more light.

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## Why does resistance increase in a filament lamp?

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.

## What happens to the resistance of the bulb as the brightness and temperature increases?

As a filament lights up, it gets hot. … So as the filament heats up the brightness increases. The increase in resistance is also happening and they all reach equilibrium when the heat radiated equals the heat dissipated.

## What happens to the resistance of a lamp as the current increases?

This heats up when an electric current passes through it, and produces light as a result. 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.

## Why doesn’t a filament lamp obey Ohm’s law?

The tungsten filament in the bulb does not follow Ohm’s law. As the voltage in the wire filament increases it heats up. The resistance of a wire changes as its temperature changes. … Often if extreme currents are applied to wires, they heat up, change their resistances, and violate Ohm’s law.

## Does brightness depend on resistance?

The brightness of a lightbulb is given by its power. P = I2R, and so brightness depends on current and resistance. … They may not, however, experience the same current. Therefore, when you are asked to rank the brightness of identical bulbs, you are really being asked to rank the amount of current through each.

## Do LED lights get brighter with more voltage?

Adjusting the voltage lower or higher will change the brightness, but only because it also changes the current- higher voltage means the current will increase in an LED. … This is measured in amperes, or amps, but since it’s such a small amount of current, LEDs will be rated in milliamps (mA).

## Does brightness increase with resistance?

High resistance bulbs are brighter in series circuits

If two bulbs in series aren’t identical then one bulb will be brighter than the other. Brightness depends on both current and voltage. Remember the current through both must be the same because the current is the same everywhere in a series circuit.

## How do I calculate resistance?

If you know the total current and the voltage across the whole circuit, you can find the total resistance using Ohm’s Law: R = V / I. For example, a parallel circuit has a voltage of 9 volts and total current of 3 amps. The total resistance RT = 9 volts / 3 amps = 3 Ω.

## Does temperature affect resistance?

Heating a metal conductor makes it more difficult for electricity to flow through it. 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.

## Do you expect the resistance of a light bulb to remain constant?

A light bulb is a simple example; the filament undergoes huge changes in temperature when current passes through it. Therefore, the resistance of the filament is not constant, rather, it increases with increased current.

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## What happens to current when voltage is increased?

Ohm’s law states that the electrical current (I) flowing in an circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, if the voltage is increased, the current will increase provided the resistance of the circuit does not change.

## What are the four things that affect the resistance of a wire?

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. 