What determines the brightness of a light bulb?

Answer 1

Generally speaking, it is the amount of applied voltagethat determines how brightly any light bulb (called a lamp) glow. This idea applies to the common incandescent lamp. For a given lamp, if we apply only a fraction of the designed operating voltage, the lamp will glow only dimly. That's because there must be "enough" voltage across a given incandescent lamp to cause it to get hot enough to incandesce, or emit light because it is very hot. The higher the applied voltage, the brighter the lamp will glow. Apply too much and the filament will be "too hot" and will be destroyed.

Answer 2

The amount of energy it uses multiplied by the efficiency at which it produces light. Two bulbs of the same power rating can produce very different levels of light depending on their efficiencies. Compact florescence bulbs are far more efficient than incandescent bulbs and produce more light for less energy.

Answer 3

The factors which affects the brightness of the bulb are:

1. Changing the number of batteries

2.Number of bulbs

3.voltage

4.The length of wire

5.Is the bulb in series or in a parallel circuit

6.Is the bulb in a complete circuit or it is broken

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Answer

There is only one factor that affects the brightness of a particular lamp. For a lamp to operate at its rated power, it must be supplied at its rated voltage. So, voltage is the one and only factor.

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To elaborate a little on the above:

There are many choices of independent variables. For example, if we know the material of the filament, the applied voltage and the current flowing through the filament we can compute the power output in the visible spectrum (i.e. the brightness). If we don't know either the current or the voltage (but know at least one of those), we can still get by provided we know the resistance of the filament at the relevant temperature. In turn, the resistance of the filament can be computed if we know its cross-sectional area and length (since we know the material and therefore the resistivity as a function of temperature). There are many possible choices, as you can imagine.

Answer 4

In Lumens, not Watts. Lumens is a measure of the perceived power of light.

Answer 5

Usually the wattage determines this

Answer 6

power input x conversion efficency