cahier physique - physics workbook

U-tube video with experiments with static electricity
http://www.youtube.com/watch?v=QxZ6AWLpnUw&feature=related

PART I : Introduction - TEST - 20 questions - 5 points per questions - yes I grade.
watch this movie and answer the questions (30 minutes)

1) The Greeks used _____________ for their electrostatic experiments (from a tree)

2) What is the origin of the name electricity ? _____________ = elektron in Greek.

3) What is the famous experiment of Ben Franklin that proved that lighting was electricity ?

4) What is a leyden jar?

5) Why Franklin was almost right when explaining electricity using one fluid model ?
What was wrong?

6) Is it the positive charges or the negative charges that are moving?

7) What is the difference between insulator and conductor?

8) lightning occurs when there is a charge ___________ due to friction.

9) rub an ebonite rod with fur and a glass rod with silk, do they collect like charges or unlike charges ? How do you know (how to find out )?

10) Look at the electron affinity chart

Hold electrons tightly
Sulfur
brass
copper
ebonite
wax
silk
lead
fur
wool
glass
hold electrons lightly

If you rub glass with wool, which is becomes + ? ___________________
if you rub an ebonite rod with fur, which one is negatively charged ? ______________
What about silk and copper ?_______________________
silk and glass ?___________________________________________

11) Which 2 materials would you use to collect more charges on each on them ?

12) What is the modern device that collect charges now day ? (it used to be the leyden jar)

13) Which part of a camera uses a capacitor ?

14) In a car, what do we use to ignite the fuel ?

15) THe build up of electric charges due to friction explain ____________ phenomena
: the electric charges are separated in a first step (the ebonite rod collects ______ charges and
the wool collects ___________ charges). In a second step the charges combine again producing
a __________.

16) The separation of positive and negative charges always means that ____________ have been transferred. (neutrons? quarks ? electrons ? protons ?)

17) the law of conservation of charge states that in an isolated system, the total charge of the system _____________________. charges within the system can be transfered from one object to another,but charge is neither __________nor _______

18) Question 17) means: total charge before = total charge after or
Qtotal before = Qtotal after (law of conservation of charges).
A) You have a rod and a cloth. They are both uncharged. So Qtotal before = ______.
You rub them together such as the rod acquires a charge of Q1 = + 10^-6 C (or E6 C) .
The cloth acquires a charge of Q2. Because of conservation of charge
Qtotal after = Qtotal before =_____ = Q1 + Q2 (sum of charges). So Q2 = _______.

B) 2 identical spherical spheres, A and B, carry charges of QA = 6 microcoulombs (6 10^-6C or 6E-6) and QB = -2 microcoulombs (-2 10^-6C pr -2E-6C), respectively. Qtotal before = QA + QB = _______. If these spheres touch, what will be the resulting charge on A ? (try without hint)
(hint: Total Q before = total Q after. And the 2 spheres are identical, they should carry the same amount of charge
after they were in contact. So QA after = QB after )

PART II: QUANTITY OF CHARGE,

LAB part1 LAB part2

1) please read and fill the blank: An elementary charge, note e, is equal, in magnitude, to the charge of one electron or one proton. So one elementary charge = 1.6 E-19C (or 1.6 10^-19 C)
The charge of a proton is + e = + 1.6 E- 19C, and the charge of an electron is -e = - 1.6 E- 19C .
Neutrons are neutral. They don't have any charge. All atoms are electrically neutral because they contain the same number of protons and electrons. As seen previously, an object (an insulator like wool or plastic) can be charged if it gains or loses electrons (by friction for example).

The net charge on a charged object is always an integral multiple of e. That is if the object is holding 2 electrons in excess, its charge will be - 2 e (that is - 2 x 1.9 10^-19C = - 3.8 0^-19C ). However, it can't hold half of an electron, or a 5.6 electrons or 10.1 electrons. Any charge stored in an object has to be a multiple of e (3e, 5e, 1000e,- 100,000 e ....). OR Q = n e
Q is the total charge , e is the elementary charge and n is the number of elementary charges in Q.
The SI of charge is the coulomb (C). One coulomb of charge is equal to ____________ elementary charges. (protons) (clue Q = ne , you are solving for n, you are given Q = 1 C and e )

2) A) So if an object has a charge of 8.0 E -19C, how many elementary charges does it hold in excess ? (use: Q = n e with Q = 8.0 E -19C) , e = 1.6 E -19C and solve for n)
Did it lose electrons or gain electrons ?
B) If the charge is - 1.6 E - 18C , how many elementary charges now?

C) which particle has no charge? (neutron? electron? proton? quark ?)

3) A) A charge of 100 elementary charges is equivalent to ________________C (solve for Q, Q = ne)
B) A charge of 200,000 elementary charges is equivalent to _______________ C

4) A strong lightning bolt transfers about 32C to EArth. How many electrons are transferred ?

PART III: COULOMB'S LAW

1) The size or magnitude of the electrostatic force Fe between 2 points charges q1 and q2 is directly proportional to the product of the charges and inversely proportional to the square of the distance d between them. This relationship is called coulomb's law. The constant of proportionality is called the electrostatic constant and noted k.
Can you translate the law in a mathematics formula?
Fe = k ___________. Use k, q1, q2. d in the formula, k is the constant of proportionality.

k= 8.99 E9 Nm²/C²

2) A)What is the electrostatic force between 2 small sphere possessing net charge of
+ 2 microcoulomb and -3 microcoulomb, respectively, if the distance between them is 10 meters?
(use Fe= Kq1q2/d², K= 8.99E9, 1 micro coulomb = E-6C convert first)
B) Is the force attractive or repulsive?

3) A point charge of 3 10^-7 C (or 3E-7 C) is placed 2 10^-2 meters (or 2 E -2 meters) from a second point charge of 4 10^-7 C ( or 4 E -7C ).
A) What is the magnitude of the electrostatic force between the charges?

B) is the force attractive or repulsive?

4) Two electrons in an atom, each with charge - 1.6 E -19C, are separated by 1.5 E -10m.
A) What is the force between them ? B) The force attracts or repels ?

5) A negative charge of -6 E -6C exerts an attractive force of 65N on a second charge 0.005m away.
A) What is the magnitude of the second charge? B) the sign of the second charge?

6) The hydrogen atom contains a proton and an electron separated by 5.0 E -11m.
Find the force of attraction between the two particles.

7) How far apart are 2 electrons if they exert a force of repulsion of 1.0N on each other ?

8) A force of - 4.4 E3N exists between a positive charge of 8 E -4 C and a negative charge of - 3 E -4C. What distance separates the charges in meters? in centimeters ?

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