Series-Parallel Circuits PDF

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what are series parallel circuits, how the operate and calculations....

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ELECTRICAL ENGINEERING

two elements wired in series. Calculate the power of the fire circuit under these conditions.

PRINCIPLES 1 - SERIES PARALLEL CIRCUITS Series-parallel circuits are circuits that consist of a combination of series and parallel circuits. All the laws governing series and parallel circuits are employed in the solution of series-parallel circuits. If the parallel circuit contains a series circuit, the series circuit must be calculated first then the parallel combination. If a series circuit contains a parallel combination then the parallel combination must be calculated first then the series combination. Exercises 1. Three resistors of resistance 10Ω, 15Ω and 30Ω are connected in parallel. A further resistor of 17Ω is connected in series with the parallel group. What is the total resistance of the combination? 2. A circuit consists of two resistors in parallel: A of unknown value and B of 10Ω. The parallel combination is connected in series with a 12Ω resistor. If the total resistance of the complete circuit is 14Ω, find the value of A. 3. A resistance combination consists of three resistors of value 8Ω, 3Ω and 1.5Ω connected in parallel. A fourth resistor of 25Ω is connected in series with the parallel group. Calculate the total resistance of the circuit. 4. Resistors of 10Ω, 15Ω and 30Ω are connected (a) in series and (b) in parallel across a 30V supply. Calculate (i) the current through the 15Ω resistor in each instance and (ii) the voltage across the 30Ω resistor in each instance. 5. A supply of 24V is applied across a resistance combination consisting of the following: three resistors of 6Ω, 12Ω, and 36Ω connected in parallel and a fourth resistor of 16.4Ω connected in series with the parallel group. Find (a) the total current, (b) the voltage across the parallel group, and (c) the current through each resistor in the parallel group.

6. A 1.750 KW two-bar fire is incorrectly wired so that the 240V supplied is connected across the

7. Calculate the value of a resistor to be connected in series with a 100W, 240V lamp so that the wattage of the lamp is reduced to 25 W. what power will be used in the resistor?

8. It is required to deliver a current of 10 A to a heater circuit at a distance from the main fuse board. Find the voltage at the heater terminals if the supply voltage at the main fuse board is 240 V and the resistance of the cable (outgoing and return) is 0.4 Ω. Calculate the wattage of the heater and the power lost in the cable.

9. A circuit consists of two groups of resistors. Group A consists of three resistors of 6Ω, 4Ω, and 12Ω connected in parallel. Group B consists of two resistors 6Ω and 12Ω connected in parallel. Groups A and B are connected in series and a supply of 36 V is connected across the combination. Find (a) the power used in the complete circuit and (b) the power in the 4Ω resistor.

10. Two resistors of 10 Ω and 40 Ω are connected in parallel. The combination is connected in series with a third resistor of 12 Ω. Calculate the voltage that must be applied to the ends of the whole circuit (a) to pass 6 A through the whole circuit and (b) to pass 6 A through the 40/q resistor. 11. Two resistors of 10Ω and 40Ω are connected in parallel. A third resistor of 5/q is connected iin series with the combination, and a dc, supply of 240 V is applied to the enda of the circuit. Calculate (a) the current in each resistor and (b) the power that be spent in a fourth resistor of 20 Ω connected in parallel with the 5Ω resistor.

12. Three resistors of value 1.5Ω, 4Ω and 12Ω are connected in parallel. A fourth resistor of 6Ω is connected in series with the parallel group. A

d.c. supply of 140 V is applied to the circuit. Calculate (a) the circuit current, (b) the value of a further resistor to be connected in parallel with the 6Ω resistor so that the potential difference across it will be 84 V, and (c) the current that will now flow in the circuit after the fifth resistor is added.

(iii) (iv) (v)

The value of R1 The total resistance The power across R2

17.

13. A d.c. supply of 240 V is applied to a circuit comprising two resistors A and B in parallel, of 5Ω and 7.5Ω respectively, in series with a third resistor C of 30Ω. Calculate the value of a fourth resistor D to be connected in parallel with C so that the total power in the circuit shall be 7.2 KW. For the circuit above determine: (i) Current in R2 (IR2) (ii) Current in R4 (iii) The voltage across the parallel group (iv) The value of R4 (v) The total resistance

14. Two resistors in parallel, A of 20Ω and B of unknown value, are connected in series with a third resistor C of 12Ω. If the p.d. across the ends or resistor C is 180 V, and the power in the circuit is 3600 W, calculate: (a) the value of resistor B, (b) the circuit voltage and (c) the current in each resistor. 15.

18.

For the circuit above determine: (i) The total resistance (ii) The circuit current (iii) The voltage across the parallel group (iv) The current through the 150Ω resistor

16.

For this circuit determine: (i) The voltage across R3 (ii) The supply voltage

Calculate: (i) The total resistance (ii) Total current (iii) The voltage across R6...