# Lighting up a fluorescent lamp with a Van De Graaf generator

• klng
In summary, a fluorescent lamp is held between two ends, A and B, with a potential difference between end A (high potential) and the hand (ground potential) causing the region between A and the hand to light up. The region between B and the hand does not light up, suggesting no potential difference between B and the hand. This could mean that end B is also at ground potential.

#### klng

Hi all,

Let's say i have the following:

I approach a charged-up VDG holding a fluorescent lamp. The end nearest the VDG is labelled A and the end furthest away from the VDG is labelled B. My hand is holding the lamp in the middle, i.e between ends A and B.

The region inside the lamp between A and my hand lights up. This is due to a potential difference between A (high potential) and my hand (ground potential). The region inside the lamp between B and my hand does not light up.

My question is this: IS there any potential difference between end B and my hand also? My understanding is that without my hand there, end B should also have a high potential,though not as high as A since it is further away from the charged up sphere. Since the region between B and my hand does not light up, i gather there is no potential difference between B and my hand. If that is the case, does it mean to say that B is now also at ground potential?

Thanks and regards.

I'd like to know the answer to this too.

Guys?

I can confirm that the region between end A and your hand will light up due to the potential difference between the high potential end A and the ground potential of your hand. This is a result of the electric field created by the charged Van De Graaf generator.

Regarding end B, there is indeed a potential difference between it and your hand, but it is not as high as the potential difference between end A and your hand. This is because end B is farther away from the charged sphere and therefore experiences a weaker electric field. However, the potential difference is still present and can be measured with a voltmeter.

The reason why the region between end B and your hand does not light up is because the fluorescent lamp requires a minimum potential difference to ionize the gas inside and produce light. This minimum potential difference is not reached at end B due to its distance from the charged sphere.

In terms of potential, it is correct to say that end B is at a lower potential compared to end A and is closer to ground potential. However, it is not entirely at ground potential because it still experiences a potential difference with your hand.

I hope this explanation helps to clarify the concept of potential difference and how it relates to lighting up a fluorescent lamp with a Van De Graaf generator. Keep exploring and asking questions, as that is the essence of being a scientist.

## 1. How does a Van De Graaf generator light up a fluorescent lamp?

A Van De Graaf generator uses static electricity to create a high voltage potential difference between its metal dome and base. When the generator is turned on, this potential difference causes electrons to flow from the dome to the base, creating a current. This current is strong enough to excite the gas inside the fluorescent lamp, causing it to emit light.

## 2. Is it safe to use a Van De Graaf generator to light up a fluorescent lamp?

Yes, as long as proper precautions are taken. Van De Graaf generators can generate very high voltages, so it is important to follow safety guidelines and use protective equipment. The fluorescent lamp itself is not in danger as the current passing through it is very low.

## 3. What type of fluorescent lamp works best with a Van De Graaf generator?

A standard fluorescent lamp, such as a T8 or T12, will work best with a Van De Graaf generator. These lamps have a gas mixture that is easily excited by the high voltage current from the generator. Specialty fluorescent lamps, such as compact fluorescent lamps (CFLs), may not work as well or at all.

## 4. Can a Van De Graaf generator light up multiple fluorescent lamps at once?

Yes, a Van De Graaf generator can light up multiple fluorescent lamps at once as long as they are connected in parallel. This means that each lamp has its own connection to the generator and does not depend on the others to function. However, the more lamps that are connected, the lower the brightness of each individual lamp will be.

## 5. Will the fluorescent lamp continue to light up after the Van De Graaf generator is turned off?

No, once the generator is turned off, the potential difference between the dome and base will disappear, and the current flow will stop. This means the fluorescent lamp will also stop emitting light. The lamp will only light up as long as the generator is creating a high voltage current.