EXPERIMENT # 2 ALL CHARGED UP! BUILDING AN ELECTROSCOPE

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Maximillian Elliott
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1 EXPERIMENT # 2 ALL CHARGED UP! BUILDING AN ELECTROSCOPE

2 VOLUNTEERS, PLEASE. Activity from p. 13 NO HAIR PRODUCTS.

3 Electroscopes test the effects of positive and negative charges Charles Du Fay, you will remember, noticed that when he brought two objects with the same charge (for example, positive/positive), they repelled each other and when he brought opposite charges together (for example positive/negative) they attracted each other.

6 Questions to think about 1. What happens when you rub the comb and plastic flag with wool? About how far away does this reaction occur? 2. What happens when you bring the comb near the charged flag after you rub the comb with plastic wrap?

7 Answers to Questions 1. When you rub the comb with the wool, the comb picks up extra electrons from the wool and becomes negatively charged. The same thing happens with the plastic flag. Since both objects have the same charge, the flag on the electroscope moves away when the charged comb comes near it. 2. Rubbing the comb with the plastic wrap removes all excess electrons along with some additional ones, so the comb has a positive charge. When you bring the positively charged comb near the negatively charged plastic flag, the two

8 The story continues In the 1700s an English scientist, Stephen Gray, continued to experiments. He made a cool discovery when he brought a charged object (think of the comb) near an uncharged one, the charge would pass through to the uncharged one, making it attract things too! Gray experimented with different charges and soon discovered that he could TRANSMIT electric charged over quite some distances!

9 He tried lots of different materials, including METAL RODS to transmit electricity. Eventually he discovered that by using WET thread, he could conduct a charge over 1/3 of a kilometer away!

10 Let s back up to what we already know. When we rub a balloon on our head, the friction causes the electrons OFF of your hair an ONTO the BALLOON. The electrons stay, Stuck, on the balloon (remember, static means, standing. ) Got it?? Most METALS, however, have atoms with, free, electrons, which move very easily from one atom to another. When you rub a piece of metal, it starts to get a charge, HOWEVER, rather than staying in place on one end like on the balloon, the charged atoms flow through the metal from one end to the other! THIS IS CALLED A CURRENT

12 FROM CURIOUSITY AND INTEREST TO PRACTICAL APPLICATIONS! It was with the understanding of CURRENT ELECTRICITY that humans have been able to make electrical energy PRACTICAL

13 All materials can conduct electricity, but some do it MUCH easier than others! Depending on its size and type, a metal wire can conduct electricity hundreds of trillions of times more effectively than a piece of glass. Objects, like metal, that can carry an electric current, are called CONDUCTORS. Objects that stop of slow the transmission of electricity are called INSULATORS

14 EXPERIMENT # 3 ALL CHARGED UP! GO WITH THE FLOW Discovering how Electric Charges can pass through different materials Activity from p. 17

15 Questions to think about 1. How does the tissue paper react to the different rods when you bring the charged balloon in contact with them? 2. Which materials would work best at transporting electricity from one place to another? Why? 3. Why do the test rods have to be placed across the plastic cup before testing them?

16 Answers to Questions 1. There is little or no reaction in the tissue paper when the charged balloon is brought near the straw and barbeque skewer. When the balloon is brought near the straightened paper clip, however, the two ends of the tissue fly apart. 2. Metal is a good conductor, whereas plastic and wood are insulators. 3. The plastic cup insulates the rods from the desktop.

17 COOL FACT A bolt of lightning can be six times hotter than the surface of the Sun A lightning bolt often heats the air around it to degrees Celsius An average lightning bolt contains between and volts of electricity

In the late 1700s two Italian scientists, LUIGI GALVANI and ALESSANDRO VOLTA

19 From the early days of Greece, through to the mid 1700s, experimenters and scientists could only experiment with STATIC electricity. In the late 1700s two Italian scientists, LUIGI GALVANI and ALESSANDRO VOLTA discovered how to make a continuous flowing CURRENT OF ELECTRICTY. LUIGI GALVANI ALESSANDRO VOLTA

It was dead, remember, so this was a bit unusual!) He was astonished and tried it again and again.

20 LUIGI GALVANI Italian Biologist in the late 1700s Studied the muscular and nervous systems of animals One day he was dissecting a frog on a copper table with a steel scalpel When he touched the dead frog with the scalpel, its leg kicked out (ummmm. It was dead, remember, so this was a bit unusual!) He was astonished and tried it again and again. He realized that the frog leg kicked only when two DISSIMILAR metals touched it (copper and steel) He incorrectly thought he had somehow activated electricity within the frogs body

Charging By Contact. Neutral objects can becomes charged through direct contact in 2 common methods:

Charging By Contact. Neutral objects can becomes charged through direct contact in 2 common methods: Charging by Contact Charging By Contact Neutral objects can becomes charged through direct contact in 2 common methods: 1. Charging By Friction When two different materials are rubbed together, electrons