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Published byLeilani Jemmott Modified over 2 years ago

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Ohm’s Law Definition Whiteboards An Elaborate Analogy

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**Ohm’s Law V = Voltage (like pressure) I = Current (like flow rate)**

+ - A R V R = V I R = Resistance in ohms () V = Voltage in Volts (V) (pressure) I = Current in Amps (A) (flowrate)

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**Ohm’s Law - The way I think of it**

V = Voltage (like pressure) I = Current (like flowrate) R = Resistance to flow + - A R V I = V R R = Resistance in ohms () V = Voltage in Volts (V) (pressure) I = Current in Amps (A) (flowrate)

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**Ohm’s Law I = V R R = Resistance in ohms ()**

+ - A R V I = V R R = Resistance in ohms () V = Voltage in Volts (V) (pressure) I = Current in Amps (A) (flowrate) Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Gray 8 White 9 Gold 5% Silver 10% No color 20% Demo - pass around resistors (two properties - power and resistance) Demo - power supply, resistor, light bulb (show increase/decrease V, and R)

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**Ohm’s Law R = V I R = Resistance in ohms ()**

+ - A 120. mA 12.0 V R = V I R = Resistance in ohms () V = Voltage in Volts (V) (pressure) I = Current in Amps (A) (flowrate) R= ?? Example 1: What is the resistance in the circuit above? R = V/I = (12.0 V)/(.120 A) = 100. Example 2: If there is a 220 resistor in the circuit above, what is the current? R = V/I, I = V/R = (12.0 V)/(220 ) = = .055 A or 55 mA

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Whiteboards 1 | 2 | 3 | 4 | 5 | 6

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What is the resistance of a light bulb if it draws 250 mA of current from a 6.15 V battery? (1000 mA = 1 A) Given: R = V I R = ?? V = 6.15 V I = .250 A R = 24.6 W 24.6

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**What current will flow if you plug a paperclip with a resistance of**

What current will flow if you plug a paperclip with a resistance of .065 into a 12 V source? Given: R = V I R = .065 V = 12 V I = ?? I = A W 180 A

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**What voltage do you need to push 1**

What voltage do you need to push 1.5 Amps of current through a 210 ohm resistor? Given: R = V I R = 210 V = ?? I = 1.5 A V = 315 V W 315 V

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**What current flows through an 8**

What current flows through an 8.1 ohm speaker when there is a voltage of 3.45 V? Given: R = V I R = 8.1 V = 3.45 V I = ?? I = I = .43 A W .43 A

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**An unknown resistor draws. 0128 Amps of current from a 23. 9 V source**

An unknown resistor draws Amps of current from a 23.9 V source. What is the resistance? Given: R = V I R = ?? V = 23.9 V I = .0128 R = R = 1870 W 1870

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A 1200 ohm resistor is hooked up to an unknown voltage source, and it draws 87.5 mA of current. What is the voltage? Given: R = V I R = 1200 V = ?? I = A V = 105 V W 105 V

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**A 670 ohm resistor is connected to a 1. 5 V battery**

A 670 ohm resistor is connected to a 1.5 V battery. What time will it take for 3.0 C of charge to flow from the battery? Given: R = V I I = q t R = 670 V = 1.5 V I = ?? q = 3.0 C t = ?? t = 1340 s W 1340 s

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A 3.0 V battery with a capacity of 350 mAh (350 milli amp hours) is drained in 4 hours and 27 minutes. What is the resistance of the circuit that it is attached to? Given: R = V I I = q t R = ?? V = 3.0 V I = ?? q = (.350e-3)(3600) = 1260 C t = 4* *60 = s R = = 38 W 38

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**A Cell. + and -, Infinite current, R = 0, what’s really inside**

Symbols + - A Cell. + and -, Infinite current, R = 0, what’s really inside A Battery of cells A resistor A voltmeter, R = infinity V3 An ammeter, R = 0 A3

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**Water in pipes: Electrons in wires: **

An analogy Water in pipes: Electrons in wires: Flow rate (GPM) Current (Amps = C/s) Pressure Voltage Constriction Resistance Constant P Pump Batteries/Cells Current convention Restriction Wires are superconductors R1 + - A3 R2

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Measuring Voltage and Current Aims Know the units of voltage and current Know how to measure voltage and current.

Measuring Voltage and Current Aims Know the units of voltage and current Know how to measure voltage and current.

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