Question

during the demonstration, answer these questions:

1. what happened to the volunteer’s hair as they touched the vandegraaff generator?
2. what happened when the volunteer moved their free hand near their charged hair?
3. what occurred when the volunteer removed their hand from the vandegraaff dome and touched something else?
4. why do you think the person was standing on books when touching the vandegraaff generator?
5. what would of happened if the person were to reach for the door knob or faucet while touching the vandegraaff generator?

Explanation:

1. When a volunteer touches a Van de Graaff generator, the generator transfers a static electric charge (usually positive) to the volunteer's body. Since like charges repel, the individual hairs on the volunteer's head, which all acquire the same type of charge, will repel each other. This causes the hair to stand on end and spread out.
2. When the volunteer moves their free hand near their charged hair, the hand is initially neutral (or has a different charge distribution). The charged hair (let's say it's positively charged) will induce a charge separation in the hand. The negative charges in the hand will be attracted to the positively charged hair, and the positive charges will be repelled. As a result, the hand will be attracted to the hair, and you may observe the hair being attracted towards the hand or the hand feeling a slight pull towards the hair.
3. When the volunteer removes their hand from the Van de Graaff dome, they are still charged (with the same charge as the dome, e.g., positive). When they touch something else (a conductor, like a metal object or another person), the excess charge on their body will flow through the conductor to the ground (or to a larger object that can act as a ground). This flow of charge is a static discharge, and it can be observed as a small spark (if the charge is large enough) and the volunteer may feel a slight shock. After the discharge, the volunteer's body will be neutral again, and the hair will fall back down.
4. The person is standing on books because books are insulators (they do not conduct electricity well). When using a Van de Graaff generator, it's important to prevent the charge generated on the volunteer's body from flowing to the ground through their feet. If they were standing on the floor (which is usually a conductor or has a path to ground, like through shoes with conductive soles or a humid environment), the charge would quickly dissipate into the ground, and the effect (hair standing on end) would be less pronounced or not occur at all. Standing on an insulator (the books) keeps the charge isolated on the volunteer's body, allowing the static charge to build up and create the desired effect.
5. If the person were to reach for a doorknob or faucet (which are typically metal conductors connected to the ground or a large conductive object) while still touching the Van de Graaff generator, the charge on their body would have a direct path to the ground through the doorknob/faucet. This would cause a static discharge to occur immediately, likely resulting in a larger and more noticeable spark (compared to when they touch something after removing their hand from the generator). The person would also feel a more significant shock, and the charge on their body would be dissipated much faster. Additionally, the flow of current through the body (even if it's a static discharge) could be potentially dangerous if the charge is very large, so this is generally not recommended during a demonstration.

Answer:

1. The volunteer's hair stood on end and spread out because the like - charged hairs repelled each other after being charged by the Van de Graaff generator.
2. The volunteer's free hand was attracted to the charged hair due to charge induction (opposite charges in the hand were attracted to the charged hair).
3. A static discharge (possibly a spark and a slight shock) occurred as the excess charge on the volunteer's body flowed to the object they touched (which acted as a ground).
4. The person stood on books (insulators) to prevent the charge on their body from flowing to the ground, so that the static charge could build up and produce the desired effect (hair standing on end).
5. A larger static discharge (spark) and a more significant shock would have occurred as the charge on the person's body would have had a direct path to the ground through the doorknob or faucet.