What does it mean for an object to be charged? What are charges? What is an atom?

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2 What does it mean for an object to be charged? What are charges? What is an atom?

3 What are the components of an atom?

4 Define the following: Electric Conductor Electric Insulator

5 Define the following: Electric Conductor A material which allows the flow of charged particles. Its internal electrons flow. Electric Insulator A material which does not allow the flow of charged particles. Its internal electrons are tightly bound to the nuclei.

6 How do you charge something?

7 Insulators can be charged by rubbing (e.g. rubbing rubber with fur.) Conductors can be charged by charge transfer.

8 Suppose two electrons are placed 1 mm apart, what do you expect to happen? Suppose an electron is placed next to a proton, what do you expect to happen? Why?

9 Opposite charges are attracted to each other. Like charges are repelled by each other. What is the charge of a proton? What is the charge of an electron?

10 Suppose two positive charges are stationary and separated some distance. If you place a negative charge in the middle with an initial velocity, what do you expect to happen?

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12 Conservation of Charge When charge is transferred between two objects, either by rubbing or a direct transfer, the number of charges lost by one object is gained by the other.

13 Coulomb s Law The force between two charges What does this resemble? k = 9.0 X 10 9 Nm 2 /C 2

14 Coulomb s Law The force between two charges What does this resemble?! " = $ % &% ' ( ' k = 9.0 X 10 9 Nm 2 /C 2

15 The Electric Field a region around a charged particle (or particles) within which a force would be exerted on other charges should they be present. The electric field (similar to a gravitational field) exists with or without a charged object to experience a force

16 Electric field lines

17 We can determine what an electric field in a particular region looks like by adding the field lines! Consider two oppositely charged particles

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19 Recall gravitational potential energy the energy of an object with mass based on its location.

20 Electric Potential Energy is similar It is the energy of a charged object based on its location.

21 Electric potential The electric potential energy per charge. Positive charges travel to a lower electric potential. Negative charges travel to a higher electric potential.

22 Electric Potential difference Often, all we care about is the difference between the electric potential of two locations this indicates the direction the charges will move.

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25 Electric Current a flow of charged particles. Units are Amperes and are typically small à 100 milliamperes across your heart is enough to be fatal! The direction current flows is defined by the direction positive charges flow. Why is this important?

26 Electric Circuits Circuits typically have a power supply or battery which creates a potential difference, a switch to turn the circuit off and on, and usually a resistance (like a light bulb).

27 Electrical resistance Resistors resist the flow of current. There are two types of circuits with resistors we will deal with: Circuits with resistors in series Circuits with resistors in parallel

28 Resistors in series Resistors in parallel

29 We can model the flow of electric current through wires the same way we look at water through tubes With the same 12V battery would you expect a larger resistance from two resistors in series or parallel?

30 The relationship between current, voltage, and resistance in a current: Ohm s law: I = V/R Recall: Power is the rate at which work is done. The power in a circuit is defined at P = IV

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32 The simple parallel circuit Consists of three identical Lamps powered by battery. When the wire at A is cut, a) Does the voltage drop across lamps 1 and 2 increase, decrease or remain the same? b) Does the current in the circuit increase, decrease or stay the same? c) What happens to the brightness of lamp 3? d) What happens to the brightness of lamp 2? e) Is the power dissipated by the circuit increased, decreased, or stay the same?