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ELECTRONICS 10: SERIES CIRCUIT
- 1. SERIES CIRCUITEMJO MAURICE N. YDIA DALLINMANARIN
- 5. CIRCUITSIn order for electricity to flow we need Power source Closed circuit There are two type of circuits we will explore Series circuit Parallel circuit
- 6. SIMPLE CIRCUITS• Series circuit –All in a row –1 path for electricity –1 light goes out and the circuit is broken • Parallel circuit – Many paths for electricity – 1 light goes out and the others stay on
- 7. SERIES CIRCUIT In a series circuit there is only one path for the electrons to flow In other words all the components are in series with each other Because there is only one path each charge will go through each resistor
- 9. SERIES CIRCUIT •A series circuit is one that has more than one resistor, but only one path through which the electricity (electrons) flows. From one end of the cell (battery), the electrons move along one path with NO branches, through the resistors, to the other end of the cell. All the components in a series circuit are connected end-to-end.
- 10. RESISTOR • A resistor in a circuit is anything that uses some of the power from the cell. In the example below, the resistors are the bulbs. In a series circuit, the components are arranged in a line, one after the other.
- 12. • Each time there is damage (break) in any one of the resistors the entire circuit will not function. For example, if one light bulb goes out, all the other lights will go off because the electricity path in the broken bulb is cut off. • Do you put Christmas lights on the trees at home during Christmas? If the lights are in a series circuit, one burned out bulb will keep all the lights off. That is one disadvantage of series circuits. One advantage though is that you will always know if there is a break in a series circuit. • If there are many bulbs in a circuit with a battery (cell), it is very likely that the light will be dimmer because many resistors are acting on the same voltage of power from the battery.
- 13. "1. THE SAME CURRENT FLOWS THROUGH EACH PART OF A SERIES CIRCUIT." • In a series circuit, the amperage at any point in the circuit is the same. This will help in calculating circuit values using Ohm's Law. • You will notice from the diagram that 1 amp continually flows through the circuit. We will get to the calculations in a moment.
- 14. "2. THE TOTAL RESISTANCE OF A SERIES CIRCUIT IS EQUAL TO THE SUM OF INDIVIDUAL RESISTANCES." • In a series circuit you will need to calculate the total resistance of the circuit in order to figure out the amperage. This is done by adding up the individual values of each component in series. In this example we have three resistors. To calculate the total resistance we use the formula: • RT = R1 + R2 + R3 • 2 + 2 + 3 = 7 Ohms
- 15. CALCULATING RESISTANCE IN SERIES CIRCUITS The rule for calculating Series Circuits is to… Add up the values of each individual in the series. R1 + R2 + R3… 5 + 5 + 10 20 Ω (ohms)
- 16. • Now with these two rules we can learn how to calculate the amperage of a circuit. Remember from Ohms Law that I = V / R. Now we will modify this slightly and say I = V / R total. • Lets follow our example figure: • RT = R1 + R2 + R3 • RT = 7 Ohms • I = V / RT • I = 12V / 7 Ohms • I = 1.7 Amp • If we had the amperage already and wanted to know the voltage, we can use Ohm's Law as well. • V = I x R total • V = 1.7 A x 7 Ohms • V = 12 V
- 17. "Voltage Drops" • Before we go any further let's define what a "voltage drop" A voltage drop is the amount the voltage lowers when crossing a component from the negative side to the positive side in a series circuit. If you placed a multimeter across a resistor, the voltage drop would be the amount of voltage you are reading. This is pictured with the red arrow in the diagram. • Say a battery is supplying 12 volts to a circuit of two resistors; each having a value of 5 Ohms. According to the previous rules we figure out the resistance.: • RT = R1 + R2 = 5 = 5 = 10 Ohms • Next we calculate the amperage in the circuit: • I = V / RT = 12V / 10 Ohms = 1.2 Amp • Now that we know the amperage for the circuit (remember the does not change in a series circuit) we can calculate what the voltage drops across each resistor is using Ohm's Law (V = I x R). • V1 = 1.2A x 5 Ohms = 6 V
- 18. "3. VOLTAGE APPLIED TO A SERIES CIRCUIT IS EQUAL TO THE SUM OF THE INDIVIDUAL VOLTAGE DROPS." • This simply means that the voltage drops have to add up to the voltage coming from the battery or batteries. • V total = V1 + V2 + V3 ... • In our example above, this means that • 6V + 6V = 12V.
- 19. "4. THE VOLTAGE DROP ACROSS A RESISTOR IN A SERIES CIRCUIT IS DIRECTLY PROPORTIONAL TO THE SIZE OF THE RESISTOR." •This is what we described in the Voltage Drop section above. •Voltage drop = Current times Resistor size.
- 20. "5. IF THE CIRCUIT IS BROKEN AT ANY POINT, NO CURRENT WILL FLOW." •The best way to illustrate this is with a string of light bulbs. If one is burnt out, the whole thing stops working.
- 21. ON THIS PAGE, WE’LL OUTLINE THE THREE PRINCIPLES YOU SHOULD UNDERSTAND REGARDING SERIES CIRCUITS: •Current: The amount of current is the same through any component in a series circuit. •Resistance: The total resistance of any series circuit is equal to the sum of the individual resistances. •Voltage: The supply voltage in a series circuit is equal to the sum of the individual voltage
- 23. •With a single-battery, single-resistor circuit, we could easily calculate any quantity because they all applied to the same two points in the circuit:
- 25. USING OHM’S LAW IN CIRCUITS WITH MULTIPLE RESISTORS
- 28. COMBINING MULTIPLE RESISTORS INTO AN EQUIVALENT TOTAL RESISTOR
- 30. CALCULATING CIRCUIT CURRENT USING OHM’S LAW
- 31. CALCULATING COMPONENT VOLTAGES USING OHM’S LAW
- 33. ANALYZING SIMPLE SERIES CIRCUITS WITH THE “TABLE METHOD” AND OHM’S LAW
- 38. •REVIEW: •Components in a series circuit share the same current: ITotal = I1 = I2 = . . . In •The total resistance in a series circuit is equal to the sum of the individual resistances: RTotal = R1 + R2 + . . . Rn •Total voltage in a series circuit is equal to the sum of the individual voltage drops ETotal = E1 + E2 + . . . En
Editor's Notes
- 1.A power source is a source of power. Most commonly the type of power referred to is: Power (physics), the rate of doing work; equivalent to an amount of energy consumed per unit time. 2. Closed circuit means a complete electrical connection around which current flows or circulates. When you have a series of electrical wires connecting to each other and completing a circuit so that current travels from one end of the circle to the other, this is an example of a closed circuit.
- A series circuit is one with all the loads in a row. There is only ONE path for the electricity to flow. If this circuit was a string of light bulbs, and one blew out, the remaining bulbs would turn off.
- Since points 1 and 2 are connected together with the wire of negligible resistance, as are points 3 and 4, we can say that point 1 is electrically common to point 2, and that point 3 is electrically common to point 4. Since we know we have 9 volts of electromotive force between points 1 and 4 (directly across the battery), and since point 2 is common to point 1 and point 3 common to point 4, we must also have 9 volts between points 2 and 3 (directly across the resistor). Therefore, we can apply Ohm’s Law (I = E/R) to the current through the resistor, because we know the voltage (E) across the resistor and the resistance (R) of that resistor. All terms (E, I, R) apply to the same two points in the circuit, to that same resistor, so we can use the Ohm’s Law formula with no reservation.
- In circuits containing more than one resistor, we must be careful in how we apply Ohm’s Law. In the three-resistor example circuit below, we know that we have 9 volts between points 1 and 4, which is the amount of electromotive force driving the current through the series combination of R1, R2, and R3. However, we cannot take the value of 9 volts and divide it by 3k, 10k or 5k Ω to try to find a current value, because we don’t know how much voltage is across any one of those resistors, individually.
- For R1, Ohm’s Law will relate the amount of voltage across R1 with the current through R1, given R1‘s resistance, 3kΩ: But, since we don’t know the voltage across R1 (only the total voltage supplied by the battery across the three-resistor series combination) and we don’t know the current through R1, we can’t do any calculations with either formula. The same goes for R2 and R3: we can apply the Ohm’s Law equations if and only if all terms are representative of their respective quantities between the same two points in the circuit. So what can we do? We know the voltage of the source (9 volts) applied across the series combination of R1, R2, and R3, and we know the resistance of each resistor, but since those quantities aren’t in the same context, we can’t use Ohm’s Law to determine the circuit current. If only we knew what the total resistance was for the circuit: then we could calculate the total current with our figure for total voltage (I=E/R).
- Combining Multiple Resistors into an Equivalent Total Resistor This brings us to the second principle of series circuits: The total resistance of any series circuit is equal to the sum of the individual resistances. This should make intuitive sense: the more resistors in series that the current must flow through, the more difficult it will be for the current to flow. In the example problem, we had a 3 kΩ, 10 kΩ, and 5 kΩ resistors in series, giving us a total resistance of 18 kΩ: In essence, we’ve calculated the equivalent resistance of R1, R2, and R3 combined. Knowing this, we could redraw the circuit with a single equivalent resistor representing the series combination of R1, R2, and R3:
- Calculating Circuit Current Using Ohm’s Law Now we have all the necessary information to calculate circuit current because we have the voltage between points 1 and 4 (9 volts) and the resistance between points 1 and 4 (18 kΩ):
- Calculating Component Voltages Using Ohm’s Law Knowing that current is equal through all components of a series circuit (and we just determined the current through the battery), we can go back to our original circuit schematic and note the current through each component:
- Now that we know the amount of current through each resistor, we can use Ohm’s Law to determine the voltage drop across each one (applying Ohm’s Law in its proper context): Notice the voltage drops across each resistor, and how the sum of the voltage drops (1.5 + 5 + 2.5) is equal to the battery (supply) voltage: 9 volts. This is the third principle of series circuits: The supply voltage in a series circuit is equal to the sum of the individual voltage drops.