When a van de graaff generator is turned on, it creates a high voltage electric field around it. This field causes your hair to become charged with the same polarity as the generator. Since like charges repel each other, your hair strands repel each other and stand up.
The high voltage electric field created by a van de graaff generator can also induce a small current in your body when you touch it. This current can cause a tingling sensation, similar to when you touch a static-charged object.
Some people may feel a stronger shock from a van de graaff generator due to differences in their body's conductivity. For example, if your skin is dry, you may feel a stronger shock compared to someone with moist skin.
No, a van de graaff generator is not dangerous to your health as long as it is used properly and not modified in any way. The shocks it produces are not strong enough to cause harm, and the electric field around it is not strong enough to cause any damage to your body.
When you touch a van de graaff generator, the electric field around it induces a small amount of charge in your body. This charge can stay on your body for a short period of time, but it will eventually dissipate as the charge equalizes with the surrounding environment.