1. Super Sparks
This challenge will introduce you to the electric charge collected on a Van de Graaff generator and the amazing things that result in the surrounding electric field. If you have already covered this in class, see how much you can remember and contribute to the rest of the group.

2. Task 3:
Investigating the parts of your Van de Graaf. With the aid of your helper, can you write down both the name and the material for each of the numbered parts below?

4. Number
Name
Material 1 2 3 4 5 6 7 8 9

5. Number
Name
Material 1
Dome
Aluminium 2
Brushes
Sometimes carbon 3
Roller
Acetate 4
Belt
Rubber 5 6
Polythene 7
Earthing point
metal 8
Discharge Sphere 9
Spark
n/a

6. Task 4: Now, time to turn it on!
Can you describe what is happening, using ALL of the key words provided below?!
friction
Build-up
electrons
transfer
charge
break-down
spark

7. As the belt is moving, the rollers transfer electrons via friction
As the belt is moving, the rollers transfer electrons via friction. The roller at the top is made from acetate, a material that is happy to transfer electrons to the belt. At the bottom, the roller is made from polythene and hence is happy to receive electrons, which are then removed from the system via the earthing point. Contact with the dome, means that electrons are removed from this metal sphere, causing a build-up of positive charged. If the discharge sphere is brought close to the dome, the opposite charge built up on both the sphere and the dome creates a large electric field, polarising then ionising the air molecules. As the constituent ions/electrons are attracted to the opposite charge, a discharge current flows; collisions with other air molecules results in the colour that we see (blue to Nitrogen ionization). We call this a spark.

8. What happens when the discharge sphere is brought closer to the main dome? (What do you see and hear?)

9. The spark is less important, quieter and less bright
The spark is less important, quieter and less bright. Less charge is permitted to build up, hence the discharge current is smaller.
Does the spark always start from the dome?

10. No. Mostly there is a spark that meets half way, or near about.
What colour is spark, and why is this?

11. Blue (NOT white). Due to collisions with Nitrogen
Blue (NOT white). Due to collisions with Nitrogen. Do not confuse with the cause of the Aurora, where Nitrogen also provide a red colour. This is ionization, not excitation.

12. Task 5:
Let’s look at the 7 different experiments that you can do. Annotate the pictures below with what you learn!

13. 1 4 3 2 5 6 7

14. Cotton threads – classic mutual repulsion
Use metal cup cake case with al foil beads – classic mutual repulsion
Soap bubbles – caution – use as few as possible and wipe clean. Moisture is a killer with these experiments. Bubbles initially attracted then rapidly repelled.
Neon lamp – strong electric field ionizing the neon and exciting the electrons that collide with the neon atoms etc
Stacked cup cake holders – mutual repulsion
Paper – mutual repulsion
Rotating wind vane – action points – charge leaving at the points causing push in the opposite direction on the vane.

15. Task 6: And to finish with, the classic!
Can you make your hair stand on end?
What is actually happening here and why do we call this phenomena Mutual Repulsion?
Are you brave enough to touch someone E. T style?!
What is the secret for making this trick work really well?

16. You need to be isolated – stand on a plastic gratnell tray
You need to be isolated – stand on a plastic gratnell tray. You pick up same charge as the dome. Your hair (if not too greasy) will mutually repel. If you turn off the Van de Graaff, your hair should fall down as the moisture in the air/leakage in the VDG causes charge to re-equalise as before.
Dry room, isolated human and making fingers not too far apart