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Chapter 6

Chapter 6. SERIES CIRCUITS. In previous units we have learned the four basic parts to make a complete circuit. The energy source The control device The conductor The load. We have also learned that loads can be connected in. SERIES PARALLEL SERIES-PARALLEL COMBINATION.

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Chapter 6

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  1. Chapter 6

  2. SERIES CIRCUITS

  3. In previous units we have learned the four basic parts to make a complete circuit • The energy source • The control device • The conductor • The load

  4. We have also learned that loads can be connected in • SERIES • PARALLEL • SERIES-PARALLEL COMBINATION

  5. In this unit we will discuss topics like • Principles of a Series Circuit • Voltage, Current, Resistance and Power in a series circuit. • Troubleshooting a series circuit using a voltmeter

  6. A series circuit provides only one path for the electrons to flow • The electrons flow from the negative side of the energy source through the load to the positive side of the energy source

  7. An opencircuit means the circuit is not complete • The switch may be in the off position • A wire could be broke • The load could be broke • Could have a loose connection.

  8. Devices like switches, fuses and circuit breakers are connected in series with the load.

  9. Polarity • It is necessary to know the polarity in DC circuits to properly connect some components and instruments (like DC meters) into the circuit. • In DC circuit the electrons flow from a negative point to a positive point.

  10. A B Which side of the resistor is positive?

  11. A B + - Which side of the resistor is positive? A

  12. VOLTAGE IN A SERIES CIRCUIT • The total voltage applied to a series circuit is automatically spread across the loads or devices in the circuit. • The voltage across any load will be that amount needed to force the electrons through the resistance of that load. • This is called a VOLTAGE DROP

  13. Voltage • Total voltage is equal to the sum of the individual voltage drops…. • Et = E1 + E2 + E3….

  14. Ohm's Law states, the voltage drop across any load in the circuit is equal to the product of the current through the load and the resistance of that load. • E = I x R • E= (Voltage drop across the load) • I= (Current through the load) • R= (Resistance of the load)

  15. KIRCHHOFF'S LAW OF VOLTAGE • In a series circuit, the sum of the voltage drops across the loads is equal to the total voltage applied to the circuit.

  16. CURRENT IN A SERIES CIRCUIT • Kirchhoff’s law states that all the current that flows into a point leaves that point. • Current remains the same through out a series circuit.

  17. Current • Total current is equal to the current flowing through any of the loads. • It = total current flowing in the circuit. • It = I1 = I2 = I3….

  18. picture circuit

  19. RESISTANCE IN A SERIES CIRCUIT • The total resistance (of the entire circuit) is the sum of all the resistances in the series circuit.

  20. Total Resistance can be calculated with this formula. • Rt = R1+ R2+ R3….

  21. Rt = R1+R2+R3 Rt = 470+220+680 Rt = 1370 Ω

  22. Determining an Unknown Voltage E I R • To find the total voltage use the formula • Et = It x Rt • To find the voltage of just one load (R1) use the formula • E1=I1 x R1 To find the voltage of resistor 2 (R2) use the formula E2 = I2 x R2

  23. Determining an Unknown Current E I R • To find the total current use the formula • It = Et / Rt • To find the current of just one load (R1) use the formula • I1=E1 / R1 To find the current of resistor 2 (R2) use the formula I2 = E2 / R2

  24. E Determining an Unknown Resistance I R • To find the total resistance use the formula • Rt = Et / It • To find the resistance of just one load (R1) use the formula • R1 = E1 / I1 To find the resistance of resistor 2 (R2) use the formula R2 = E2 / I2

  25. Determining an Unknown Power P E I • To find the total Power use the formula • Pt = Et x It or Pt = P1 + P2…. • To find the power of just one load (R1) use the formula • P1 = E1 x I1 • To find the power of just one load (R2) use the formula • P2 = E2 x I2

  26. Troubleshooting a Series Circuit • One of the most common circuit faults in a series circuit is an open. (open-circuit) • A voltmeter, combined with the knowledge of the laws of voltages, is a quick and easy method of analysis.

  27. Troubleshooting a Series Circuit with a Voltmeter • To begin the troubleshooting process, measure to determine if there is voltage at the supply. (If the voltage is good move to the fuse.) • Take a voltage drop reading across the fuse. A good fuse will not produce a voltage drop. • A blown fuse will produce a voltage drop that is equal to the source voltage.

  28. Troubleshooting a Series Circuit with a Voltmeter • Also check the voltage drop across the switch. • The closed switch should not produce a voltage drop. • A SPST switch that produces a voltage drop when closed is defective.

  29. Troubleshooting a Series Circuit with a Voltmeter • Next, check to see if there is a voltage drop across the individual resistors. • If a resistor connected in a series circuit is open, it will have a voltage drop equal to the source voltage. (The other resistors will have no voltage drop at all.)

  30. If the source is delivering the voltage, move to the next step.

  31. If the source is delivering the voltage, move to the next step. • Notice that the switch is open, how is there still voltage on the meter?

  32. When the switch is open the voltmeter will read a full 6 volts.

  33. When the switch is closed, the voltmeter will indicate zero volts.

  34. With the switch open the meter will read zero volts across the load.

  35. With the switch closed, the amount of the voltage drop will be shown by the meter.

  36. The End

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