Class 10 Chapter 1 Electricity Physics Solution S.Chand. Part 6

 PART VI Page 47

DOMESTIC ELECTRIC CIRCUITS : SERIES OR PARALLEL

Very Short Answer Type Questions

1. Are the lights in your house wired in series ?

No, the lights in my house are not wired in series. They are typically wired in parallel.

2. What happens to the other bulbs in a series circuit if one bulb blows off ?

In a series circuit, if one bulb blows off, it breaks the circuit and all the other bulbs will go out as well.

3. What happens to the other bulbs in a parallel circuit if one bulb blows off ?

In a parallel circuit, if one bulb blows off, the other bulbs will remain lit because each bulb has its own separate path for current to flow.

4. Which type of circuit, series or parallel, is preferred while connecting a large number of bulbs :

(a) for decorating a hotel building from outside ?

(b) for lighting inside the rooms of the hotel ?

(a) For decorating a hotel building from outside, a parallel circuit is preferred because if one bulb blows off, the rest will remain lit, ensuring the entire decoration is still illuminated. (b) For lighting inside the rooms of the hotel, a parallel circuit is also preferred for similar reasons. It provides redundancy, so if one light fails, the others will continue to function.

5. Draw a circuit diagram to show how two 4 V electric lamps can be lit brightly from two 2 V cells.

Here's a circuit diagram showing how two 4V electric lamps can be lit brightly from two 2V cells:

+-------[ 2V ]-----[ 4V Lamp ]-----[ 2V ]--------+ | | [+] | [2V Cell]------------------------------------------+---> to the other lamp [-] | | | +-------[ 2V ]-----[ 4V Lamp ]-----[ 2V ]--------+

Each 2V cell is connected in series with a 2V lamp, and then these pairs are connected in parallel to the other pair. This setup allows the lamps to receive the required voltage to light brightly.

Short Answer Type Questions

6. Why is a series arrangement not used for connecting domestic electrical appliances in a circuit ?

A series arrangement is not used for connecting domestic electrical appliances because if one appliance fails or is disconnected, it breaks the circuit, causing all the other appliances in the series to stop working. This is highly impractical for domestic use where we want the flexibility to operate appliances independently. 7. Give three reasons why different electrical appliances in a domestic circuit are connected in parallel.

Three reasons why different electrical appliances in a domestic circuit are connected in parallel are:

• Independence: Each appliance operates independently of the others, so if one appliance fails or is disconnected, it does not affect the operation of the others.
• Voltage Stability: Appliances receive the same stable voltage regardless of the number of other appliances connected to the circuit.
• Convenience: It allows for easier installation, maintenance, and replacement of individual appliances without affecting the rest of the circuit.

8. Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line. (a) Which circuit would have the highest voltage across each bulb ? (b) In which circuit would the bulbs be brighter ? (c) In which circuit, if one bulb blows out, all others will stop glowing ? (d) Which circuit would have less current in it ?

(a) The parallel circuit would have the highest voltage across each bulb. In a parallel circuit, each bulb receives the full voltage of the power supply independently, whereas in a series circuit, the voltage is divided among the bulbs. (b) The bulbs would be brighter in the parallel circuit. This is because each bulb in a parallel circuit receives the full voltage of the power supply, whereas in a series circuit, the voltage is divided among all the bulbs. (c) In the series circuit, if one bulb blows out, all others will stop glowing. This is because in a series circuit, the failure of one component interrupts the entire circuit. (d) The parallel circuit would have less current in it. In a parallel circuit, the current is divided among the branches, so each bulb receives only a fraction of the total current. In a series circuit, the current is the same throughout, so each bulb receives the full current of the circuit.

9. Consider the circuits given below :

(a) In which circuit are the lamps dimmest ? (b) In which circuit or circuits are the lamps of equal brightness to the lamps in circuit (i) ? (c) Which circuit gives out the maximum light ?

(a) Circuit (ii) (b) Circuit (iii) (c) Circuit (iii)

10. If you were going to connect two light bulbs to one battery, would you use a series or a parallel arrangement ? Why ? Which arrangement takes more current from the battery ?

For connecting two light bulbs to one battery, a parallel arrangement would be preferred. The reason for choosing a parallel arrangement is that it allows each light bulb to operate independently of the other. This means that if one light bulb were to fail or be removed, the other would still function normally. Additionally, each bulb receives the full voltage of the battery in a parallel arrangement, ensuring consistent brightness. In terms of current consumption from the battery, the parallel arrangement would draw more current compared to a series arrangement. This is because in a parallel arrangement, each bulb draws current directly from the battery separately, effectively doubling the current drawn from the battery compared to a single bulb. In contrast, in a series arrangement, the same current flows through both bulbs, so the total current drawn from the battery remains the same as if only one bulb were connected.

Long Answer Type Question

11. (a) Which is the better way to connect lights and other electrical appliances in domestic wiring : series circuits or parallel circuits ? Why ? (b) Christmas tree lamps are usually wired in series. What happens if one lamp breaks ? (c) An electrician has wired a house in such a way that if a lamp gets fused in one room of the house, all the lamps in other rooms of the house stop working. What is the defect in the wiring ? (d) Draw a circuit diagram showing two electric lamps connected in parallel together with a cell and a switch that works both lamps. Mark an A on your diagram to show where an ammeter should be placed to measure the current.

(a) Parallel circuits are the better way to connect lights and other electrical appliances in domestic wiring. This is because parallel circuits offer several advantages over series circuits, such as:

• Independence: Each appliance operates independently, so if one fails or is disconnected, it does not affect the operation of the others.
• Voltage Stability: Each appliance receives the full voltage of the power supply independently, ensuring consistent performance.
• Convenience: It allows for easier installation, maintenance, and replacement of individual appliances without affecting the rest of the circuit.

(b) If one lamp in a series circuit of Christmas tree lamps breaks, it interrupts the circuit, causing all the other lamps in the series to go out as well. This is a characteristic of series circuits where the failure of one component interrupts the entire circuit.

(c) The wiring defect in the electrician's setup is that all the lamps in the house are connected in series. This means that if one lamp gets fused (blown out) in one room, it breaks the circuit, causing all the lamps in other rooms of the house to stop working. This wiring setup is highly impractical for domestic use as it lacks the independence and reliability provided by parallel circuits.

(d) Circuit diagram:

+---[ Lamp A ]---+ | | [Cell]----[ Switch ]--+---[ Ammeter (A) ] | | +---[ Lamp B ]---+

In this diagram, the ammeter (A) should be placed in series with the switch to measure the current flowing through both lamps when the switch is closed.

Multiple Choice Questions (MCQs)

12. The lamps in a household circuit are connected in parallel because : (a) this way they require less current (b) if one lamp fails the others remain lit (c) this way they require less power (d) if one lamp fails the others also fail

(b) if one lamp fails the others remain lit

In a parallel circuit, each lamp operates independently of the others. Therefore, if one lamp fails, it does not affect the operation of the other lamps. This is a significant advantage of parallel circuits and a key reason why household lamps are connected in parallel.

13. Using the circuit given below, state which of the following statement is correct ?

(a) When S1 and S2 are closed, lamps A and B are lit. (b) With S1 open and S2 closed, A is lit and B is not lit. (c) With S2 open and S1 closed A and B are lit. (d) With S1 closed and S2 open, lamp A remains lit even if lamp B gets fused.

(c)

Questions Based on High Order Thinking Skills (HOTS)

14. (a) Draw a circuit diagram showing two lamps, one cell and a switch connected in series. (b) How can you change the brightness of the lamps ?

(a) Circuit diagram showing two lamps, one cell, and a switch connected in series:

+---[ Lamp 1 ]---[ Lamp 2 ]---+ | | [Cell]-------------------------[ Switch ]

(b) To change the brightness of the lamps in a series circuit, you can do the following:

1. Change the Voltage: If the cell used in the circuit is adjustable or replaceable with one of different voltage, you can change the voltage supplied to the circuit. Increasing the voltage will typically increase the brightness of the lamps, and decreasing the voltage will decrease the brightness.

2. Change the Resistance: You can alter the resistance in the circuit, either by using resistors in series with the lamps or by using lamps of different resistances. Increasing the resistance in the circuit will decrease the current flowing through it, thus reducing the brightness of the lamps. Conversely, decreasing the resistance will increase the current and brightness.

3. Use Dimmer Switch: If the switch used in the circuit is a dimmer switch, you can adjust the brightness by varying the resistance in the circuit. Dimmer switches typically work by altering the amount of resistance in the circuit, thereby controlling the amount of current flowing to the lamps and consequently adjusting their brightness.

15. Consider the circuit given below where A, B and C are three identical light bulbs of constant resistance.

(a) List the bulbs in order of increasing brightness. (b) If C burns out, what will be the brightness of A now compared with before ? (c) If B burns out instead, what will be the brightness of A and C compared with before ?

(a) Brightness Order:

1. C (Brightest)
2. A = B (Equal Brightness)

(b) Bulb C Burns Out:

The brightness of A will remain the same.

Here's why:

• Bulbs A and B are connected in parallel.
• In a parallel circuit, each component receives the full voltage from the source.
• Burning out bulb C doesn't affect the path of current for A and B.
• Therefore, the voltage across A and the current flowing through it remain unchanged, keeping its brightness the same.

(c) Bulb B Burns Out:

• The brightness of A will be zero.
• Bulb C's brightness remains the same.

Here's why:

• Bulbs A and B are in series.
• In a series circuit, all components share the same current.
• If B burns out, the current flow in the entire circuit stops.
• Since there's no current, bulb A won't receive any electrical energy, resulting in no light (zero brightness).
• Bulb C is in a separate branch of the circuit, and the burning out of B doesn't affect its current flow or brightness.

16. How do you think the brightness of two lamps arranged in parallel compares with the brightness of two lamps arranged in series (both arrangements having one cell) ?

The brightness of two lamps arranged in parallel would typically be brighter compared to two lamps arranged in series, provided that the voltage across both arrangements remains the same (i.e., one cell is used for both arrangements). In a parallel arrangement, each lamp receives the full voltage of the cell independently. Therefore, each lamp operates at its maximum brightness, and the total brightness of the arrangement is the sum of the brightness of each individual lamp. In a series arrangement, the same current flows through both lamps, and the voltage is divided between them. As a result, each lamp receives only a fraction of the voltage, leading to reduced brightness compared to when the lamp operates at its full voltage. However, if the lamps used in the series arrangement have a higher resistance or are designed to operate at a lower voltage, they may appear brighter than expected due to the lower voltage across them. Nonetheless, in most cases, lamps arranged in parallel would appear brighter than those arranged in series when powered by the same voltage source. 17. If current flows through two lamps arranged : (a) in series, (b) in parallel, and the filament of one lamps breaks, what happens to the other lamp ? Explain your answer.

(a) In a series arrangement:

If the filament of one lamp breaks in a series arrangement, the other lamp will also go out. This occurs because in a series circuit, the current flows through both lamps in a continuous loop. When one lamp's filament breaks, it creates an open circuit, interrupting the flow of current. Since the current path is broken, no current can flow through the circuit, and both lamps are affected.

(b) In a parallel arrangement:

If the filament of one lamp breaks in a parallel arrangement, the other lamp remains lit. This is because each lamp in a parallel circuit has its own separate branch connected directly to the power source. Therefore, even if one lamp fails and its filament breaks, the other lamp's circuit remains unaffected, allowing it to continue receiving current and emitting light independently.

18. The figure below shows a variable resistor in a dimmer switch.

How would you turn the switch to make the lights : (a) brighter, and (b) dimmer ? Explain your answer.

(a) Turn the switch to right side (b) Turn the switch to left side.