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Equivalent Resistance, Volts, Amps. Volts and Amps in a Series Circuit. In a series circuit, the Amps remain constant throughout the whole circuit. Amps = 2A. Amps = 2A. Amps = 2A. Volts and Amps in a Series Circuit.
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Voltsand Amps in a Series Circuit • In a series circuit, the Amps remain constant throughout the whole circuit Amps = 2A Amps = 2A Amps = 2A
Voltsand Amps in a Series Circuit • However, in a series circuit at each resistor the volts change. When you add up all the voltage at each resistor, you end up getting the total volts going through the circuit. Volts3 = 2V Volts total = 7V Amps = 2A Volts2 = 3V Amps = 2A Amps = 2A Volts1 = 2V
Voltsand Amps in a Parallel Circuit • In a parallel circuit, each line of wire has a different amount of amps. When added the amps together, you get the total amount of amps in the entire circuit. Amps3 = 1A Amps2 = .5A Amps3 = .5A Amps tot = 2A
Voltsand Amps in a Parallel Circuit • However, in a parallel circuit if you have a total of 3 volts in the circuit, each resistor will only have 3 volts Volts3 = 3V Amps3 = 1A Volts2 = 3V Amps2 = .5A Amps1 = .5A Volts1 = 3V Volts Total = 3V Amps tot = 2A
Equivalent or Total Resistance - Req • Equivalent Resistance is the TOTAL resistance of a circuit • Symbol: Req or Rt • Units: Ω Ohms • Formula: Series: Req = R1 + R2 + R3 + … Parallel:
5 W 3 W 10 W Example #1: What is the equivalent resistance (Req) of the circuit below? • Type of circuit: Series • Formula: Req = R1 + R2 + R3 • Req = 10 + 5 + 3 • Req = 18 W
75 W 30 W Example #2: What is the equivalent resistance (Req) of the circuit below? • Type of circuit: Series • Formula: Req = R1 + R2 • Req = 75 +30 • Req = 105 W
Example #3: What is the equivalent resistance (Req) of the circuit below? 10 Ω 15 Ω Type of circuit: Parallel Formula: 1 ÷ 0.1666 = 6Ω
What is the equivalent resistance (Req) of the circuit below? 15 W 5 W 15 W Example #4: Type of circuit: Parallel Formula: 1 ÷ 0.3333 = 3Ω
KEY POINTS • Symbols of circuit parts: • Voltmeter, Ammeter, Power Supply, Resistor • Two types of circuits (series and parallel) • Formula for Req (equivalent resistance) Series – Req = R1 + R2 + R3 • Parallel -
Simulations • Open up applications for simulation • Or go to http://phet.colorado.edu/en/simulations/category/physics
Colour coding on resistors • Resistors are coated with ceramic. • They have color coded bands to indicate resistance
Resistor Example: If you have a resister that is red, orange and yellow Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Gray 8 White 9 First colour is red, thus first digit is 2 and the second colour is orange, thus the second digit is 3 = 23 The third colour is yellow, and this digit is 4 we therefore find 104 = 10000 This resistance would be 10000 X 23 = 230 000 W