1. Introduction to circuits, Coulomb Law.
Friday, March 10, 2017

2. Friday, 3/10 Unit: Circuits
What would life be like if we did not
have batteries?
2. What would you miss the most if you did
not have batteries?
Upcoming dates:
Note: you will have a HWK check or quiz each class

4. What is electric current?
The continuous flow of electrons (electric charge) through a conducting metal.
Current is the rate at which the electrons (energy); meaning it is the energy per unit of time
I = ΔQ / Δt
I = charge/s

5. What requirements are there in order for current to exist?
A source of electric potential energy which we call voltage (V).
This is the source that gives the the charges energy (volt = 1 Joule/coulomb).
The charges need a conductive path; example metal (metals are conductors) wire.
the charges repel each
causing the charge to move

6. Relating current to what we know about energy.

7. Types of current Alternating Current
Flow of current that periodically changes direction
Produced in power plants
Current from a wall outlet changes direction 120 times per second
Direct Current
The flow of current in one consistent direction
Examples
Batteries
Solar cells
Current from a battery travels from the positive terminal to the negative terminal.

8. Common Language

9. Note Taking Guide Quantity Symbol Definition Unit Measuring Device
Potential difference
current
resistance

10. Current
The continuous flow of electrons (electric charge) through a conducting metal.
Current is the rate at which the electrons (energy); meaning it is the energy per unit of time
Measured in amperes (A)
I = ΔQ / Δt
I = charge/s

11. a device that measures current
Ammeter
a device that measures current
attached in series

12. Potential difference
Potential difference (also voltage (V) can be thought of as the force pushing electric charges along a conductor. Voltage between two points creates an electric field.
Measured in Volts (V)
V = UE /Q
(volt = 1 Joule/coulomb).

13. electric potential difference, must be connected in parallel
Voltmeter
a device that measures
electric potential difference,
must be connected in parallel

14. Resistance
Resistance (R) is a measure of how difficult it is to push the charges along. The less difficult it is the better conductor it is.
The energy is transformed at the resistor (potential energy is converted).
Examples: light bulb, charging your phone, making coffee, etc.
Measured in Ohms ()
Resistance is dependent on
The material which is measured by resistivity
The length of the conductor (more resistance for greater length (L)
The width (the wider it is the lower the resistance (A)

15. Note Taking Guide Quantity Symbol Definition Unit Measuring Device
Potential difference V
Energy in the circuit
Volts
Voltmeter
current I
Rate of flow
Amperes
Ammeter
resistance R
Opposes current
OhmsΩ
Ohmmeter

16. Electrical Circuit Terminology
Circuit – a path that allows electricity to flow
Circuit diagram – a simplified representation of an electrical circuit that shows only the electrical connections of elements in a circuit.
We will study two types of circuits:
Series circuit
Parallel circuit

17. Electrical Circuit Terminology

18. Ohm’s Law V = I * R I = V/R R = V/I
Ohm's Law analyzes the relationship between voltage and current in an ideal conductor.
Ohm's Law is given by:
V = I * R
I = V/R
R = V/I

19. Example
A flashlight that is powered by 3 volts and uses a bulb with a resistance of 60 ohms. What is the current flowing through the circuit?

20. Practice
Ohm’s Law 1