Chapter 7 Section 2

What Is Electric Current? - net movement of electric charges (electrons) in a single direction - measured in amperes

This diagram shows a simple LED driver circuit This diagram shows a simple LED driver circuit. When the battery is connected the positive end of the battery pulls electrons from the negative end of the battery and through the circuit. This circuit has three basic properties: voltage, current, and resistance.

What Is a Voltage (Potential) Difference? - the force that causes electrons to flow - electric charge flows from a higher voltage to a lower voltage

Circuit = a closed path that electric current follows This flow of electrons can power things like light bulbs

Batteries Dry cell battery is the most common type of battery. It is called a dry cell because the electrolyte is a moist paste and not a liquid solution. Wet cell battery is a battery that contains a series of wet liquid solution cells connected together. Lead-acid battery is the type used in cars. It is like the wet cell battery in that is a series of cells connected together immersed in a liquid. The liquid in this specific type of battery is a sulfuric acid solution and the plates in the battery are made specifically of lead.

Resistance = tendency for material to oppose the flow of electrons  -- electric current loses energy as it flows -- resistance is measured in OHMS   * Copper has a low resistance, hence it is used for household wiring and other electronics

STOP AND THINK 1. A positively charged subatomic particle is ____         negatively charged  subatomic particle is ____ 2.  Amperes are used to measure  _________ 3.  A closed path that electrons (current) can flow through is a: 4.  Materials that current can flow through easily are called: 5. OHMS are used to measure the __________ of a circuit.

As the length of a wire increases, so does its resistance As the wire becomes thinner, its resistance increases the thin wire in a tungsten light bulb glows due to this resistance

Ohm's Law --  the current (I) in a circuit equals the voltage difference  (V) divided by resistance (R)

Quick Calculations: 1.  What is the current of a circuit with a voltage difference of 20 volts and a resistance of 10 ohms. 2.  What is the Voltage difference  in a circuit with a resistance of 11 ohms, and a current of 2 amperes. 

1.  What is the center of an atom called? 2.  Electrons are attracted to _________ 3.  Electrons move from the ___ to the ___ side of a battery. 4.  What is the most common metal used in wiring? 5. How many volts are in an AA battery? ______ 6.  How many volts are in a wall outlet?  7. A device used to turn electricity on and off is a _______ 8. In which type of circuit can you turn a light off and the other will stay on?  [  series / parallel ]