ART AND ELECTRICITY ORIGINS

Transcription

1 CIRCUITS!

2 ART AND ELECTRICITY ORIGINS Film Kinetic sculpture Light art La Coquille et le Clergyman (The Seashell and the Clergyman) - Germaine Dulac, 1928 Rotary Demisphere (Precision Optics) Marcel Duchamp, 1925 Light-Space Modulator László Moholy-Nagy, 1930

3 ELECTRICITY - FLOW Energy from the flow of electrons (subatomic particles with negative elementary electric charge) A material that allows electrons to flow through it is said to be conductive Examples: copper, aluminum, brass, nickel, iron, steel A non-conductive material used to block the flow of electrons is called an insulator Examples: the coating around an electrical wire

4 AC/DC AC alternating current: Switches directions periodically. This is what standard electrical outlets use. DC direct current: Always one direction (positive to negative). This is what batteries use. We will only be working with DC in this class. The convention is to describe the flow of electricity from the positive terminal of a power source to the negative

5 ELECTRICITY - TERMS Current Amount of electric charge flowing over time Measured in Amperes (amp or A) Voltage Level of charge Measured in Volts (V) Resistance Reduction of flow of electricity Measured in Ohms (Ω)

6 WATER ANALOGY Positive terminal higher elevation Negative terminal low elevation Current amount of water flowing over time Voltage the pressure of the water flow Resistance Rocks and other obstructions that slow the water flow

7 CIRCUIT Circuit A continuous path of conductive material from the positive terminal of a power source to the components being powered (e.g. a light) and ultimately to the negative source. Short circuit A path directly from positive to negative with no components being powered (BAD!) When you are making a circuit, if nothing is being powered, detach the power source and check for short circuits If components in your circuit heat up, detach the power source immediately

8 LED Light-emitting diode Electric current only flows in one direction Current from positive terminal flows into anode (long leg) Current exits from cathode to negative terminal (short leg)

9 OHM S LAW Describes the relationship between current, voltage, and resistance I = V / R I Current V Voltage R Resistance Voltage = power source voltage minus the voltage drop in the circuit LED current 20 ma LED voltage drop: Red, yellow, and green ~2 V Blue and white ~3 3.5 V

10 RESISTORS Supply resistance to a circuit Current can flow either direction Identified based on colored stripes

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12 SCHEMATICS Schematic simplified 2D diagram of a circuit Shows the path of the electric flow (not the specific physical layout/dimensions) Battery LED Resistor

13 SERIES CIRCUIT There is only one path from the positive to negative terminal of the battery Voltage is divided among the components

14 PARALLEL CIRCUIT Multiple separate paths for electric flow Start with a fork in the path and end with a convergence Each parallel path gets the same full voltage flowing to that part of the circuit

15 QUESTION 1 Using Ohm s law, if we are using a 9V battery to power a single LED with a voltage drop of 2 V, and we want 20mA of current, how much resistance does the circuit need? I = V / R R = V / I I = 0.02A V = 9V 2 V = 7 V R = 7 V / 0.02A = 350 Ω Test it out!

16 QUESTION 2 If we are using a 9V batter to power two 3.4 V LEDs wired in series, how much resistance do we need? 110 Ω Test it out!

17 SWITCHES Poles number of circuits a switch can control Throw-count number of positions to which each pole can connect SPST single pole single throw turns a circuit on/off by connecting/disconnecting Schematic symbol: SPDT single pole double throw switches between two paths Schematic symbol:

18 SWITCH EXERCISE 1 Make a switch that turns three LEDs of the same color on/off at the same time. Draw the schematic first

19 SWITCH EXERCISE 2 Make a switch that switches between at least 2 LEDs of one color and at least 2 LEDs of another color. Draw the schematic first