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

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

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

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

Relating current to what we know about energy.

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.

Common Language

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

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

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

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).

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

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)

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

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

Electrical Circuit Terminology

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

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?

Practice Ohm’s Law 1