1. Equivalent Resistance, Volts, Amps

2. Volts and Amps in a Series Circuit  In a series circuit, the Amps remain constant throughout the whole circuit Amps = 2A

3. Volts and 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. Amps = 2A Volts 2 = 3V Volts 1 = 2V Volts 3 = 2V Volts total = 7V

4. Volts and 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. Amps 3 = 1A Amps 2 =.5A Amps 3 =.5A Amps tot = 2A

5. Volts and 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 Amps 3 = 1A Amps 2 =.5A Amps 1 =.5A Volts Total = 3V Volts 1 = 3V Volts 2 = 3V Volts 3 = 3V Amps tot = 2A

6. Equivalent or Total Resistance - Req  Equivalent Resistance is the TOTAL resistance of a circuit Symbol:Req or R t Units:Ω Ohms  Formula: Series: Req = R 1 + R 2 + R 3 + … Parallel:

7. 5  3  10  Type of circuit:Series Formula:Req = R 1 + R 2 + R 3 R eq = 10 + 5 + 3 R eq = 18  What is the equivalent resistance (Req) of the circuit below?

8. 30  75  Type of circuit:Series Formula:Req = R 1 + R 2 R eq = 75 +30 R eq = 105  What is the equivalent resistance (Req) of the circuit below?

9. Type of circuit:Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 10 Ω 15 Ω 1 ÷ 0.1666 = 6Ω

10. Type of circuit:Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 1 ÷ 0.3333 = 3Ω 15  5  15 

11. 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 = R 1 + R 2 + R 3  Parallel -

12. All the Information you need

13. Simulations  Open up applications for simulation  Or go to http://phet.colorado.edu/en/simulat ions/category/physics http://phet.colorado.edu/en/simulat ions/category/physics

14. Colour coding on resistors  Resistors are coated with ceramic.  They have color coded bands to indicate resistance 1 st & 2 nd band first two digits of resistance 3 rd band Number of zeros to add after the first two numbers. I.E. 10 1, or 2, or 3….

15. Resistor Example: If you have a resister that is red, orange and yellow Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9 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 10 4 = 10000 This resistance would be 10000 X 23 = 230 000 