Friday, 2/14 – Coulomb ’ s Law

1. Friday, 2/14 – Coulomb’s Law • Respond to the following: • What is a force? • Do you think forces have an impact on the way charges react? Explain your answer. • Upcoming Dates: • Electricity teston Friday, 2/21

2. Induction, conduction, and Coulomb’s Law

3. charging a rod and electroscope positively and negatively by conductionand induction When charging by conduction, the rod touches the electroscope. The electroscope gets thesame chargeas the rod. When charging by induction, the roddoes not touchthe electroscope. The electroscope gets theopposite chargeof the rod.

4. Induction Example

5. Conduction Example

6. COULOMB’S LAW The force between two charged objects is directly proportional to the product of their charges and inversely proportional to their separation distance squared. link1

7. In equation form: q1 q2 = Felectric kc d2 F is the force of attraction, measured in newtons, between charges q1 and q2 k is the Universal Electrostatic Constant, equal to 9.00 x 109 Nm2/C2 q1 and q2 are the attracting charges, measured in coulombs d is the distance between the charges, and is measured in meters

8. The SI unit of charge is the coulomb, named in honor of Charles Augustin Coulomb.

9. Most of the time you will be given μC and will need to convert to Coulomb’s • How to convert… • Number will become 10-6 • Example: 6 μC = 6 x 10-6 Coulomb’s unit of measure

10. Example Problem # 1 What is the electrostatic force between two objects, +13 μC and –22 μC which are 0.055 m apart?

11. What does the sign tell us? • If both charges have the same sign, they will repeleach other. • + Fel means objects repulse each other • If the charges have opposite signs, the will attract each other. • - Fel means objects attract each other

12. Example Problem # 2 What is the electrostatic force between two objects of -14 μC and -22 μC that are .86 m apart?