1. Glencoe Physics Chapter 23 ”Circuits and Circuit Elements"

2. Electric Circuits b b In each of the following, a circuit will be drawn consisting of a direct current power source of 12V potential, a switch, a lamp, an ammeter, and a fuse. b b 1. Pictorial b b 2. Block b b 3. Schematic - schematic symbols. b b You are required to know the schematic symbols on page 731 and practice drawing them.

3. Diagramming Electric Circuits b b When drawing schematic diagrams, follow these steps. b b 1. Draw the symbol for the source with the negative terminal at the top. b b 2. Draw the wire to connect the device; i.e., resistor, capacitor. b b 3. If you reach a point with two paths, make sure the two paths join again. b b 4. Continue until you reach the positive terminal of the battery. b b 5. Check to make sure you have included all components of the circuit. b b Assignment: Page 735, 1-4

4. Resistors in series or in parallel b b In this chapter you will be required to distinguish between series and parallel circuits in several instances. b b A series circuit is one in which there is a single conducting path. b b A parallel circuit is one in which there is more than one conducting path.

5. Series Circuit b b You should remember the following characteristics of a series circuit. b b 1. Current is constant in a series circuit. b b I T = I 1 = I 2 = I 3 b b 2. Total resistance is equal to the sum of each individual resistance. b b R T = R 1 + R 2 + R 3 b b 3. Total voltage is equal to the sum of each individual voltage. b b V T = V 1 + V 2 + V 3

6. Sample Problem b b Three resistors are wired in series to a 24V power source. The values of the resistors are 4ohms, 6ohms, and 2ohms respectively. Draw the diagram (schematic) of the circuit and find the total resistance, the current in each resistor, and the voltage drop across each resistor. b b Assignment: Page 623, Problems 11-14

7. Parallel Circuits b b 1. Current is additive in a parallel circuit. b b I T = I 1 + I 2 + I 3 b b 2. Total resistance is the sum of the reciprocals of the individual resistors. b b 1 1 1 1 b b ------ = ------ + ------ + ----- b b R T R 1 R 2 R 3 b b 3. Voltage is constant in a parallel circuit. b b V T = V 1 = V 2 = V 3

8. Sample Problem b b Three resistors are wired in parallel to a 24V source. The resistors have values of 4ohms, 6ohms, and 2 ohms respectively. Draw the diagram and find the total resistance, the total current, and the current flow in each resistor. b b Assignment: Page 626, Problems 15-19

9. Real circuits contain series and parallel wiring. Ohm's law can be applied to any separate portion of a circuit. The following basic concepts should be followed in solving series-parallel circuit problems b b 1. Find the total resistance. Begin with the portion of the circuit the greatest distance from the power source and work your way back to the source using Ohm's Law on each series and/or parallel part. b b 2. Find the total current using Ohm's law, the total resistance, and the voltage of the source. b b 3. Find the current in each portion of the circuit by applying Ohm's law to each series and parallel portion of the circuit. Remember, current is constant in the series portion of the circuit and voltage is constant in the parallel portion of the circuit. You should begin at the power source and work toward the end of the circuit.

10. Sample Problem b b In the given circuit, find; b b 1. the total resistance b b 2. the total current in the circuit b b 3. the current in each resistor b b 4. the voltage drop across each resistor b b Assignment: Page 751 Practice 20D b b Page 752 Section Review