Brightness of a bulb: what determines it?

Susan Fernandez January 01 2022

When we tell the brightness of a bulb we mean that it's luminosity. It is defined as the total amount of energy that a light source emits per second across all wavelengths.

What are the inconveniences of having something too bright or too low?

Besides problems with eyesight, especially if the light beam falls into our eyes, there are physiological reasons for this. A human being has built-in reflexes which allow us to protect ourselves from overexposure to light. The issue is very important since without these controls we wouldn't be able to see them at all. Too much brightness would literally blind us.

What is the standard of bulb brightness?

For the human eye, sensitivity luminosity is measured in units called candelas. If we know the distance from which a source of light can be seen, then we can calculate its brightness by dividing the power it emits by this distance. This way we have a known value that indicates how much energy a person should receive per second to see properly under ideal conditions.

There are cases when the environment around us doesn't allow us to use maximum appliances because total darkness isn't present nor complete illumination. In such areas, for example in caves or along roadsides where lighting is sparse at night, our eyes adapt and become more sensitive to even small segments of light. Therefore if their sensitivity level changes then this factor must be taken into account when measuring the brightness of bulbs.

Most people accept some level of variation in their daily routines but there are times when they seek the best possible luminosity. This means that they don't require extra-bright light sources, just more of it for a given time interval.

The opposite situation occurs with fans of low brightness for extended periods of time. As mentioned before if something doesn't have to be extremely bright then it is better not to use it at all and save energy.

Does voltage, current, or wattage affect the brightness?

The brightness of a bulb is determined by the voltage that passes through it. This makes sense when we understand that light, just like any other form of energy, can be converted from one form to another. In this case, the electrical power goes from being potential in a source to kinetic when electromagnetic waves are emitted in a bulb.

The change happens in bulbs with an incandescent filament in which electricity goes through a very thin wire and heats it up so much that it emits all sorts of forms of radiation including visible ones. An example would be the Sun whose surface temperature is about 6,000 kelvins (K). The color seen depends on wavelength since some areas emit infrared radiation while others appear yellow-white or even blue due to their high temperature.

The light bulb in your lamp at home has a much lower rate of evaporation, about 2,500 K. That means that instead of being bright red it emits blue-white light which seems to be pleasant for most people. But there are others with different preferences who would opt for infrared or yellow rather than blue lights. This issue is usually resolved by fitting the appliance with colored filters that change the color of emitted radiation to something more familiar and comfortable for them.

The current`s effect on the brightness of any bulb depends on the type of filament. In incandescent bulbs, when the current increases so do its temperature and if it gets too hot then it melts. In other types of lamps based on different principles, this isn't the case unless there is a short circuit that causes an abnormal increase in current.

Finally, wattage is a measure of electricity flow rate and not brightness. However, it is worth noting that the most common household bulb type, the incandescent one, has a linear relationship between voltage and wattage. The higher the former the greater the latter meaning that this aspect shouldn't be neglected if we want to use our bulbs more efficiently.

Resistance and bulb brightness

This factor is as important as any of the three discussed above and yet it has been largely ignored since resistance is measured in ohm (Ω). It represents opposition to current inside an appliance and for this reason, its value affects brightness, not directly but indirectly.

First of all, we have to see that the bulb's filament doesn't generate light by itself. Instead, the electric current flowing through it emits electromagnetic waves which shine outwards from its surface.

This means that if a filament resists this flow then less power will be transferred to it meaning that fewer photons will be generated after passing through the wire. In other words, energy wasted due to resistance can lead to lower brightness although there are other factors involved such as voltage drop between electrodes which could compensate for some of the lost energy.

Secondly, the resistance of each household appliance is usually printed on its label. Since most of them are for incandescent bulbs it is clear that they have to be operated at higher voltages than those recommended by their manufacturers. For this reason, all appliances classified as being "120 volts" actually work with about 130V which means that the resistance should be lower in order to avoid wasting energy.

The relationship between brightness and resistance can also be explained via Ohm's law. It states that current flow across a wire is directly proportional to the voltage difference between electrodes divided by total resistor resistance. This means that if we vary the first factor but keep the other two constant, then brightness will change proportionally so long as there is no short circuit or high temperature which would cause problems.

Does connection matter?

Whether you have parallel or series circuits, each one of them should be capable of transferring the same amount of electricity. But this isn't always the case since we usually connect several appliances to a single source and it would be logical to think that if we double voltage then brightness will also double.

If we placed two bulbs in series with each receiving 110V (efficiency = 100%) then such doubling would take place (efficiency = 200%). However, if they were placed in parallel then instead of increasing brightness by 1.8 times as expected, you would get 3 times as much (i.e., efficiency = 300%). This is because these two circuits behave differently so only the latter offers a suitable level for both lights.

Eventually, a bulb's wattage is determined by its resistance and the amount of power it is capable of receiving from an outlet. However, what we perceive as brightness depends on both factors as well as voltage drop throughout each appliance (which requires a more complex calculation).

Resistive losses inside an appliance can't be ignored since they represent a significant portion of its energy consumption which is why we should search for ways to reduce them. It doesn't matter if you're trying to save electricity for your own benefit or just want to help out our planet: both goals can be reached by applying some basic knowledge about household appliances and then using this information with prudence and common sense.

What bulb type is the brightest?

LED, incandescent, CFL, and halogen lamps all use electricity to produce light but the last one is different from the rest since it doesn't contain mercury which would pose a threat if broken. This makes it an ideal choice for examining the role of resistance in brightness considering that we will be comparing two similar devices, not something vastly different like CFL and LED lamps.

Both types work with a tungsten filament which emits electromagnetic radiation when electric current flows through it. The major difference between them is that incandescent bulbs don't have built-in protective features such as those included in halogen ones. Due to this fact they tend to dry out after some time which affects their performance as well as lifespan so they are less reliable than other models.

Incandescent bulbs have a higher resistance than halogen lamps which means they will consume more electricity while glowing. This is why it's always better to choose lower wattage versions since they produce the same amount of light but consume less energy. In the case of incandescent lamps, this is why it's always better to choose lower wattage versions since they produce the same amount of light but use less power.

At this point, we know that brightness depends on neither voltage nor wattage but these two factors determine how much electricity a bulb can receive from a source. That being said, if you placed both bulbs in series then their resistances would add up, and thus halogen lamp would be brighter because its resistance is lower (5Ω vs 11Ω). It might sound trivial but this is the main difference between these types of bulbs.

CFLs are very energy-efficient but their light quality often leaves much to be desired (due to lack of instant start and flicker which can cause eye strain). On average, they use 1/4th the amount of electricity required by incandescent lamps while lasting 8 times longer. However, their price is higher than LED ones which means they aren't a cost-effective solution for many people. They also contain mercury which makes them harder to recycle.

LED lamps are currently considered the best alternative to incandescent bulbs since they are capable of producing very good light quality (instant start, high flicker frequency which makes them suitable for homes) while using less energy than CFLs. High prices prevent these lights from becoming mainstream but their efficiency is increasing every year so it's only a matter of time before this happens.

Halogen lamps have an excellent color rendering index because tungsten filament doesn't release infrared radiation. This means that they can help you create warm-colored ambiances but also cost twice as much as CFLs do. After comparing all four types it becomes clear that LED ones are the most efficient ones although not necessarily the cheapest to buy.

How can I determine my light level?

To know how much light you need in any given situation, whether it be for work or recreation purposes, you should download an application such as Illuminance from Google Play or App Store depending on your device`s OS. With this tool you will be able to see what luminosity is comfortable for your eyes without making them tired and also how different lighting conditions affect your daily routines.

Without this app, you can calculate luminosity yourself by knowing that 1 lumen per square ft is equal to 10.76 lux or 0.093 foot-candles (FC). Good practices in lighting, both in outside and inside environments also affect our general well being which is why it's worth investing in different tools that measure the degree of luminosity at any given time.

The other thing that should be kept in mind is that there are many misconceptions about the different types of lamps and their efficiency. This means that it's always better to check facts before deciding what to buy since a lack of knowledge can make you spend more money than necessary.

Bottom line

  1. To determine how much light a bulb emits you should use an illuminance meter which will tell you exactly how much lumen it produces.
  2. The brightness of a bulb depends on several factors including resistance, wattage, and voltage but the most important one is the type of lamp. Halogen lamps are the brightest ones followed closely by incandescent models whereas CFLs and LED lights to produce less luminosity.
  3. In order to find out what kind of lighting would be appropriate for your work or hobbies, you can install Illuminance from Google Play or App Store and see how different values affect your everyday life in both subtle and obvious ways.
  4. There are four main types of lights but only some have practical applications for your everyday tasks. Halogen lamps are the best in terms of brightness but also cost twice as much as CFL ones do. LED ones are slightly less efficient than halogens but they're getting better every year which means that their price might drop quite soon.
  5. When buying any kind of lamp, it's always better to have some basic knowledge about what factors affect light levels so you don't need to spend more money than necessary for different lighting conditions.