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
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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.
 Spring '11
 Lewis

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