Chapter 11.3 Electric Current upload/1220_A006N.jpg

D4 Explain the relationship among voltage, current and resistance in a simple series circuit.

Remember: Stationary electrons = Moving electrons =

Remember: Stationary electrons = static electricity Moving electrons = electrical current comp/ART/ART158/TOT007.jpg commiechink.com/.../static.gif

Circuit – This is where electrons are moving in a closed and continuous pathway. There are 3 components to a circuit: 1.Source of electrons 2.Pathway through which to travel 3.Source of energy “push” or “pressure” to move electrons

A V Battery Wire Switch Resistor (this can be something that uses electricity) Parts of a circuit Voltmeter Ammeter Bulb

Types of Circuits Resistors in circuits can be connected in 2 ways Series Parallel V3V3 V1V1 V2V2 R3R3 R1R1 R2R2 I I I3I3 I2I2 I1I1

Series Circuit

Series Circuits The electricity in this type of circuit only has ONE PATH to follow. If the circuit is interrupted, the flow of electricity will STOP.

Types of Circuits Series – resistors lie along a single pathway in the circuit. Amount of current is the same anywhere in the circuit. (same amount of current to do work; work done at the resistors) Resistance is additive. All resistors are affected. V3V3 V1V1 V2V2 R3R3 R1R1 R2R2 I Req = R 1 + R 2 + R 3 etc….. Req – resistance equivalent If resistors are added, all lights would get dimmer. If resistors were taken away all lights would get brighter. What would happen if 1 light burnt out? Hint: Each resistor acts like a switch

Parallel Circuit

Parallel Circuits The flow of electricity has MORE THAN ONE path to follow. If the flow of electricity is disrupted, the electricity may be able to find another pathway

Types of Circuits Parallel- current flows through many pathways & resistors lie on different pathways. Each pathway only draws the current it needs,  the current is split, but the voltage is the same through out. I I3I3 I2I2 I1I1

Sources of energy for electrical current Electrochemical Cells – aka “Batteries” Chemical reactions can be transformed into electrical energy Chemical Energy  Electrical Energy

Wet Cells e.g. car battery Electrodes – plates made out of: lead (Negative electrode) and lead oxide (Positive electrode) Liquid Conductor (Electrolyte Solution) Electrodes are immersed in electrolyte Sulfuric Acid. images/c00011.jpg

Chemical reaction between lead, lead oxide, and sulfuric acid release e-s images/c00011.jpg Electrons move from negative lead electrode to positive lead oxide electrode through the sulfuric acid electrolyte

Dry Cells - similar to wet cells, but electrolyte is “Dry” (not water) e.g. Zinc electrode Carbon electrode Ammonium chloride electrolyte Wires are connected to electrodes to conduct electrons “from” and “back to” the battery. a05_img01.gif

Types of Current DC – Direct Current, electrons flow in one direction AC – Alternating Current, electrons flow in one direction first, then in the opposite direction American homes use AC electricity that changes directions 120 times per second

Current – rate at which electric charge flows through the wire. Measured by counting the number of electrons passing by a specific point in the circuit in one second. Current Symbol -  Measured in amperes (amps) Amperes Symbol - A

Voltage – amount of electric energy available by potential difference to move electrons. More Voltage = More Work Remember (w = f  d) Voltage Symbol - V Measured in volts - V

Resistance – force opposing the flow of electrons in the current Good conductors = low resistance Poor conductors = high resistance Resistance Long wires > Short wires Thin wires > Thick wires Hot wires > Cool wires > Means greater than

Resistance symbol – R Measured in ohms Ohms Symbol -  (Greek letter omega) home.att.net/ ~basicelectronics/ohmchart.gif Born: 16 March 1789 in Erlangen, Bavaria (now Germany) Died: 6 July 1854 in Munich, Bavaria, Germany

Power Equation P = I × V Power (watts) = current (A) x voltage (V) Watts is the information that you typically associate with a light bulb

Ohm’s Law I = V/R V =   R R = V /  I = current V= voltage R= resistance

Remember Ohm’s Law V = IR For a series circuit, since the current is the same throughout the circuit, then: V = V 1 + V 2 + V 3 + etc….  V = IR 1 + IR 2 + IR 3 + etc..  V = IR eq  R eq = R 1 + R 2 + R 3 + etc… (R eq = Resistance equivalent) I V R V1V1 V2V2 V3V3 R1R1 R2R2 R3R3

- + V = 12v I R1R1 R2R2 R3R3 Type of circuit ___________ R eq = I = R 1 = 50  R 2 = 100  R 3 = 40 

- + V = 12v I R1R1 R2R2 R3R3 Type of circuit = Series R eq = R 1 + R 2 + R 3 = 50   + 40  = 190  I = V / R eq = 12v / 190  = A R 1 = 50  R 2 = 100  R 3 = 40 

Homework Read text pp Complete SR pg. 607 #1-4, and 6