Resistors - Resistors Resistors Overview Overview...

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Unformatted text preview: Resistors Resistors Overview Overview Resistance is measured in Ohms (Ω) Resistance value of a resistor is measured from its bands Resistance can be changed by putting resistors in parallel or series The resistor The What a resistor is What Metal Connector Carbon Body Color Bands Color First band is the first digit Second band is the second digit Third band is the multiplier Fourth band is the tolerance 1 Reading the bands Reading 0 X 10 = 100Ω What is the resistance? What Use your resistance chart to calculate the resistance of the following resistor 2 Answer Answer 0 X 100 = 2000Ω Tolerance Tolerance Tolerance is the % error allowed for the given resistance shown in Gold 5%, Silver 10% and none at all 20%. Gold = 5% tolerance Tolerance Tolerance Example • A 5% tolerance for a 100 Ω resistor means that the resistor can have a value of ± 5% of 100. • 100 Ω X .05 = 5 Ω • Therefore the resistor must be within 5 Ω of the initial 100 Ω resistance Playing with resistance Playing A pencil can be used to simulate a resistor. 10k Connecting Resistance Boxes Connecting 200kΩ Group Work Group Use the multi­meters to experiment with different resistance bars using a #2 Pencil. Symbol in a circuit Symbol Ohms Law Ohms V=IR V = Voltage I = Current R = Resistance V I R Simple Calculation Simple What is the resistance on a circuit with a 5v power source and 1A of current? Answer Answer V = IR 5v = (1A)(x) R = 5 Ω Series Circuit Series R1 R2 Resistors in series Resistors Resistance Total (Rt) Rt = R1 + R 2 So… if R1 = 50 Ω and R2 = 100 Ω what is the total resistance? Answer Answer Rt = R1 + R 2 Rt = 50Ω + 100Ω Rt = 150Ω Series Circuit Series R1 R2 Current is same throughout a series circuit Resistance total is the sum of all resistors Resistance = Voltage / Current The sum of the voltage drops across components in a series circuit equals the potential difference. Parallel Circuit Parallel R1 R2 Resistors In Parallel Resistors Resistance total (Rt) Rt = 1 1 1 + R1 R 2 So… if R1 = 50 Ω and R2 = 100 Ω what is the total resistance? Answer Answer Rt = 1 1 1 + 50 100 Rt = 1 2 1 + 100 100 1 1 1 Rt = = Rt = = 33.3Ω 3 .03 .03 100 Parallel Circuit Parallel R1 R2 The voltage across each parallel branch is the same. Current total in a parallel circuit is the sum of the currents flowing through each parallel branch. Current total = Applied Voltage / Resistance total. Combination Combination What is the resistance of this circuit? 500 150 500 Answer Answer Remember the formulas: 1 • Resistors in parallel = • Resistors in series = Resistance Total (RT) = 1 1 + R1 R 2 R1 + R 2 ÷ 1 1 ÷+ R 3 1 ÷ + R1 R 2 Resistance Total = RT = 400 Ω ÷ 1 1 ÷+ 150 1÷ + 500 500 Question Question If the circuit from the previous slide had a power source of 12v, what was the current running through the circuit? Remember V=IR Answer Answer V = IR V = 12v R = 400 Ω I = 12v / 400 Ω = .03A Potentiometers Potentiometers A variable resistor • • Volume control Light bulb dimmer Potentiometer Potentiometer 100 Ω Potentiometer Potentiometer 8k Ω Symbol in a circuit Symbol Good Job Good ...
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This note was uploaded on 10/23/2011 for the course DESHIGN AN 1910265 taught by Professor Lewis during the Spring '11 term at Thomas Jefferson School of Law.

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