Electricity: Circuits and Their Components – Long Answer Type Questions

Q1. What is electricity? Explain its importance in our daily life with suitable examples.

Ans. Electricity is a form of energy produced by the flow of electric charges (electric current) through a conductor. It is one of the most important sources of energy in our daily life.

Its importance can be understood from the following points:

• We use electricity to light our homes, schools, streets and offices using bulbs, tube lights and LEDs.
• It runs electrical appliances such as fans, televisions, refrigerators, mixers, coolers and computers.
• In schools and offices, electricity powers projectors, printers and computers, making work easier.
• Electricity is used in hospitals to run life-saving machines like X-ray, ECG and ventilators.

Thus, electricity has become essential for comfort, communication, education and healthcare.

Q2. Define an electric circuit. Describe with the help of a simple example how an electric circuit is formed in a torch.

Ans. An electric circuit is a closed and continuous path along which electric current flows from one terminal of a cell or battery, through electrical components, back to the other terminal.

In a torch:

• Two or more cells are arranged in a row to form a battery.
• Wires inside the torch connect the positive terminal of the battery to one terminal of the bulb and the negative terminal to the other terminal of the bulb through a switch.
• When we press the switch ON, the circuit becomes closed. Current flows from the battery, through the bulb filament and back to the battery.
• Due to this current, the filament becomes hot and starts glowing, and the torch gives light.

Thus, a torch is a simple example of an electric circuit in daily life.

Q3. Differentiate between an open circuit and a closed circuit. How does the state of the circuit affect the glowing of a bulb?

Ans. The difference between an open circuit and a closed circuit is:

• Closed circuit: The path of current is complete without any gap. Current flows from one terminal of the cell, through the components, back to the other terminal. In this case, if the bulb and cell are working, the bulb glows.
• Open circuit: The path of current is broken due to a gap, loose connection, open switch or broken wire. Since the path is incomplete, current cannot flow and the bulb does not glow.

Thus, a bulb glows only in a closed circuit, and it does not glow in an open circuit, even if all components are good.

Q4. Explain why it is important for students to learn about simple electric circuits at the school level.

Ans. Learning about simple electric circuits at school is important because:

• It helps students understand the basic working of day-to-day devices such as bulbs, torches, fans and doorbells.
• It develops a scientific attitude, where students learn to reason out why an appliance is not working (for example, open circuit, fused bulb, weak cell).
• Students become aware of safety rules related to electricity, which protects them from accidents and electric shocks.
• It lays the foundation for further studies in Physics and electrical engineering in higher classes.

Therefore, knowledge of electric circuits is both practically useful and academically important.

Q5. What are conductors and insulators? Why are both of them necessary in an electric circuit and in household wiring?

Ans. Conductors are materials that allow electric current to pass through them easily. Metals like copper and aluminium are examples. Insulators are materials that do not allow current to pass through them easily. Plastic, rubber, glass and dry wood are examples.

Both are necessary for the following reasons:

• Conductors such as metal wires are used to make the path of current in a circuit.
• Insulators are used as coverings on wires and handles of tools to prevent current from entering our body.
• Household wiring uses copper or aluminium wires for conduction, but these wires are fully covered with plastic insulation to make them safe to touch.

Hence, conductors ensure that current can flow where needed, while insulators ensure that it does not flow where it can be dangerous.

Q6. What is an electric cell? Describe its structure and working in simple terms.

Ans. An electric cell is a small device that converts chemical energy into electrical energy.

Structure:

• It has a positive terminal, usually a raised metal cap.
• It has a negative terminal, usually a flat metal base.
• Inside the cell, there are chemicals that react with each other.

Working:

• A chemical reaction inside the cell produces a potential difference between the two terminals.
• When the cell is connected in a closed circuit, this potential difference pushes charges and a current flows through the circuit.
• As the cell is used, the chemicals slowly get used up. When they are almost finished, the cell becomes “weak” or “dead”.

Thus, a cell is the basic source of electric energy for small circuits.

Q7. Define a battery. Explain how cells are connected to form a battery and why we sometimes need batteries instead of a single cell.

Ans. A battery is a combination of two or more electric cells connected together in a proper way.

Formation:

• Cells are usually connected in such a way that the positive terminal of one cell is joined to the negative terminal of the next cell.
• The free negative terminal of the first cell and the free positive terminal of the last cell act as the two terminals of the battery.

Need for batteries:

• Some devices need more energy or a higher voltage than a single cell can provide.
• A battery made of several cells can make bulbs glow brighter or run devices like torches and toys for a longer time.

Hence, we use batteries whenever a single cell is not sufficient for the required purpose.

Q8. Why should the two terminals of a cell never be connected directly without a device or resistance between them?

Ans. Connecting the two terminals of a cell directly with a wire is called a short circuit.

This should be avoided because:

• There is almost no resistance in the path, so a very large current can flow.
• Such high current can cause the cell and wire to become very hot and may damage them.
• The cell will get discharged quickly and might even leak or burst in extreme cases.

Therefore, a cell must always be connected through a suitable device, such as a bulb or resistor, to avoid short circuits.

Q9. Explain what happens to a cell after long use. How can you identify that a cell has become “dead” in a simple circuit?

Ans. After long use, the chemicals inside a cell are almost used up and cannot produce enough potential difference. Such a cell is called a dead cell or discharged cell.

We can identify a dead cell by:

• Connecting it to a simple circuit with a bulb and switch. If the circuit is complete but the bulb does not glow, the cell may be dead.
• In devices like torches or remotes, if they stop working even with correct connections, the cells may need to be replaced.

Thus, a dead cell can no longer run electrical appliances properly and must be replaced by a fresh cell.

Q10. List any four common devices in which batteries are used. Why are batteries very important in modern life?

Ans. Four common battery-operated devices are:

• Torch
• TV remote control
• Wall clock
• Mobile phones and tablets (rechargeable batteries)

Batteries are very important because:

• They provide a portable source of energy, so devices can be used anywhere without direct wiring.
• They are essential in many emergency devices like torches and emergency lights.
• Modern gadgets such as mobiles, laptops and cameras cannot work without batteries.

Thus, batteries have made our life more comfortable and mobile.

Q11. Describe the main parts of an electric bulb. How does an electric bulb produce light?

Ans. The main parts of an electric bulb are:

• A glass bulb that encloses the inner parts and protects them from air.
• A thin filament of tungsten wire inside the bulb.
• Support wires and a metal cap with two terminals for connecting the bulb to the circuit.

Working:

• When electric current passes through the filament, the filament offers some resistance to the flow of current.
• Due to this resistance, electrical energy changes into heat energy and the filament becomes red hot.
• At this high temperature, the filament starts glowing and gives out light.

Thus, an electric bulb converts electrical energy into light and heat.

Q12. What is a fused bulb? Explain why a fused bulb does not glow even in a closed circuit.

Ans. A fused bulb is a bulb whose filament has broken due to overheating or long use.

It does not glow in a closed circuit because:

• The filament is the part of the bulb through which current flows. When it breaks, there is a gap in the path of current inside the bulb.
• This gap behaves like an open circuit, even though the external wires are properly connected.
• Since the current cannot pass through the broken filament, the bulb does not get heated and does not glow.

Therefore, a fused bulb must be replaced to complete the circuit and make the lamp glow again.

Q13. A student makes a simple circuit with a cell, wires and a bulb, but the bulb does not glow. List and explain any four possible reasons.

Ans. The bulb may not glow due to the following reasons:

• Fused bulb: The filament inside the bulb may be broken, so current cannot pass through it.
• Open circuit: There may be a gap in the circuit due to loose connections or a broken wire, so the circuit is not closed.
• Wrong connections: The cell may be connected incorrectly, for example both wires touching only one terminal of the cell.
• Dead cell: The cell may be weak or dead and unable to provide enough current to light the bulb.

By checking these points one by one, the student can find and correct the fault in the circuit.

Q14. Why do electric bulbs often become hot when they are glowing? How should we handle them safely?

Ans. When a bulb glows, electric current passes through the filament, which offers resistance. Due to this, electrical energy is converted into heat energy and the filament becomes very hot. The heat is transferred to the glass bulb, so the bulb also becomes hot.

Safe handling:

• We should never touch a glowing bulb or a bulb just switched off, as it can cause burns.
• Always switch off the power and wait for the bulb to cool before changing or handling it.
• Use proper holders and avoid touching the metal parts while the power is on.

These precautions help us use bulbs safely without getting hurt.

Q15. Define conductors and insulators. Explain with examples how you would test a material to find out whether it is a conductor or an insulator.

Ans. Conductors are materials that allow electric current to pass through them easily, such as copper and aluminium. Insulators are materials that do not allow electric current to pass through them easily, such as plastic, rubber and glass.

To test a material:

• Make a simple circuit with a cell, a bulb and two wires.
• Leave a small gap between the two wires and place the test material in that gap.
• If the bulb glows, the material allows current to pass and is a conductor.
• If the bulb does not glow, the material is an insulator.

Thus, using a simple circuit, we can classify materials as conductors or insulators.

Q16. Explain why electric wires are made of metals but are covered with plastic or rubber.

Ans. Electric wires are made of metals like copper or aluminium because:

• Metals are good conductors of electricity.
• They offer low resistance, so current can pass easily with little energy loss.

These metal wires are covered with plastic or rubber because:

• Plastic and rubber are insulators, which do not allow current to pass through.
• They prevent electric shocks if someone touches the wire.
• They also protect the metal wires from damage due to moisture or other objects.

Thus, the combination of metal conductor and insulating cover makes electric wires both efficient and safe.

Q17. Tap water conducts electricity but distilled water does not. Explain this statement.

Ans. Pure distilled water contains almost no dissolved salts, so it has very few ions. Since electric current in liquids is carried by ions, distilled water is a poor conductor of electricity.

Tap water, on the other hand, contains various dissolved salts and minerals.

• These dissolved salts provide charged particles (ions) that can move and carry current.
• Therefore, tap water can conduct electricity and may make a bulb glow in a suitable circuit.

Hence, the presence of dissolved salts and ions makes tap water a conductor, while distilled water remains almost an insulator.

Q18. Why should we not touch electrical appliances with wet hands? Explain the role of water in this situation.

Ans. We should not touch electrical appliances with wet hands because:

• Water, especially tap water, contains dissolved salts and impurities which make it a conductor of electricity.
• When our hands are wet, a path is created for electric current to pass from the appliance through our body to the ground.
• This can cause a dangerous electric shock, which may harm or even be fatal.

Therefore, we must always dry our hands before touching plugs, switches and other electrical devices to stay safe.

Q19. What is an electric switch? Describe its function in a circuit and give one example of its use in daily life.

Ans. An electric switch is a device used to open or close an electric circuit.

Function:

• When the switch is ON (closed), it completes the circuit and allows current to flow.
• When the switch is OFF (open), it breaks the circuit and stops the flow of current.

Example:

• We use wall switches at home to switch on or off lights and fans. By flipping the switch, we either complete the circuit (appliance works) or break it (appliance stops).

Thus, switches help us safely control electrical appliances without directly touching the wires.

Q20. What is a circuit diagram? Why do we use symbols instead of drawing actual pictures of components?

Ans. A circuit diagram is a simplified diagram of an electric circuit using standard symbols to represent different components such as cells, bulbs, switches and wires.

We use symbols because:

• They make the diagram simple and neat, easy to draw and understand.
• Actual pictures of components would be complicated and take more time to draw.
• Standard symbols are understood by everyone, so circuit diagrams can be shared and read universally.

Therefore, circuit diagrams using symbols are a convenient way of representing electrical circuits.

Q21. Draw and explain a simple circuit diagram showing a cell, a bulb and a switch. Describe the flow of conventional current in it.

Ans. (You may draw the diagram in your notebook.) A simple circuit diagram consists of:

• A symbol of a cell – two parallel lines, the longer line showing the positive terminal and the shorter line showing the negative terminal.
• A symbol of a bulb – usually a circle with a small curved filament or cross inside.
• A symbol of a switch – a small gap in the line with a movable link that can connect or disconnect the line.
• Lines representing connecting wires, joining all components in a loop.

Flow of conventional current:

• When the switch is closed, the circuit is complete.
• Conventional current flows from the positive terminal of the cell, through the switch, then the bulb, and finally back to the negative terminal of the cell.

This completes the circuit and the bulb glows.

Q22. Why is it not advisable to connect the switch in parallel with the bulb in a simple circuit?

Ans. In a simple circuit, the switch should be connected in series with the bulb so that it can control the flow of current through the bulb.

If the switch is connected in parallel with the bulb:

• When the switch is closed, it provides an alternative path of very low resistance.
• Most of the current flows through the switch branch instead of the bulb.
• As a result, the bulb may not glow at all, even though the circuit is complete.

Therefore, to properly control the bulb, the switch should always be in series with it.

Q23. What is meant by series connection of components in a circuit? Explain with an example and state one disadvantage of series connection in household wiring.

Ans. In a series connection, components are connected one after another in a single path so that the same current flows through each component.

Example:

• Connecting two bulbs end-to-end with a cell so that current passes through the first bulb and then through the second in a single loop.

Disadvantage in household wiring:

• If one bulb or appliance connected in series fails or is removed, the circuit becomes open.
• As a result, all other appliances in that series connection also stop working.

Hence, series connection is not suitable for household wiring, where each appliance should work independently.

Q24. What is a parallel connection? Why is parallel connection preferred over series connection in household wiring?

Ans. In a parallel connection, components are connected in separate branches between the same two points in a circuit. Each branch has its own path for current.

Parallel connection is preferred in home wiring because:

• Each appliance gets the same voltage as the power supply, so they work properly.
• If one appliance or bulb stops working or is switched off, others in parallel branches continue to work.
• Each appliance can be controlled by its own switch, allowing independent operation.

Therefore, parallel connection makes household wiring safer, more convenient and efficient.

Q25. Explain the heating effect of electric current. Give two examples where this effect is useful.

Ans. When electric current flows through a conductor, part of the electrical energy is converted into heat energy. This is called the heating effect of electric current.

Useful examples:

• Electric iron: Current passes through a high-resistance coil inside the iron, heating it. This heat is used to press clothes.
• Electric heater or geyser: A coil (heating element) gets hot when current flows through it, warming water or air.

Thus, the heating effect is deliberately used whenever we need to convert electrical energy into heat.

Q26. What is an electric fuse? Describe its construction and explain how it protects an electrical circuit.

Ans. An electric fuse is a small safety device used in circuits to protect appliances and wires from getting damaged due to excessive current.

Construction:

• It consists of a thin wire made of a material with a low melting point.
• The fuse wire is fixed between two terminals and is usually enclosed in a small cartridge or fuse holder.

Working and protection:

• Under normal current, the fuse wire allows current to pass safely.
• If the current becomes too high due to short circuit or overloading, the fuse wire heats up and melts.
• This breaks the circuit and stops the flow of current, protecting appliances and wires from overheating and fire.

Thus, a fuse sacrifices itself to save the rest of the circuit.

Q27. State any five safety rules that you should follow while using electricity at home or in school.

Ans. Five important safety rules are:

• Never touch switches, plugs or appliances with wet hands.
• Do not insert fingers, metal objects or wires into a plug point or socket.
• Do not overload a single socket with too many appliances at the same time.
• Never touch or repair loose or naked wires; inform an elder or an electrician.
• Always switch off the main power before changing bulbs or repairing electrical equipment.

Following these rules greatly reduces the risk of electric shocks and accidents.

Q28. A house has lights and fans connected in parallel. Explain what happens to other appliances if one bulb fuses. Why is this arrangement advantageous?

Ans. In a parallel connection:

• Each appliance has its own separate branch connected to the power supply.
• When one bulb fuses, only that branch is affected. The path of current in other branches remains complete.
• Therefore, other appliances continue to work normally, even if one bulb fails.

This arrangement is advantageous because:

• Failure of one device does not disturb the working of others.
• Each appliance can be switched on or off independently according to need.

Hence, parallel wiring is convenient and reliable for homes and buildings.

Q29. How does an electric iron use the heating effect of current? What precautions should be taken while using an electric iron?

Ans. An electric iron has a heating element made of a high-resistance wire fixed inside its base.

Working:

• When the iron is plugged in and switched on, current flows through the heating element.
• Due to resistance, electrical energy is converted into heat, and the base of the iron becomes hot.
• This heat is then used to press clothes and remove wrinkles.

Precautions:

• Never touch the hot metal base of the iron.
• Always keep the iron on a suitable stand when not in use.
• Switch off the iron when you are not using it to avoid overheating and fire risk.
• Ensure that the wire and plug are not damaged to prevent electric shock.

By following these precautions, we can use an electric iron safely and effectively.

Q30. Summarise the main ideas of the chapter “Electricity: Circuits and Their Components” that are important from the examination point of view.

Ans. Important ideas from this chapter are:

• Electricity and circuit: Electricity is energy due to moving charges; an electric circuit is a closed path for current.
• Cell and battery: A cell converts chemical energy into electrical energy. A battery is a combination of cells.
• Bulb and filament: The filament glows when current passes; fused bulb has a broken filament and does not glow.
• Conductors and insulators: Conductors allow current (metals), insulators do not (plastic, rubber).
• Switch and circuit diagrams: Switch controls current; circuit diagrams use standard symbols to represent components.
• Series and parallel connections: Series – one after another, if one fails all stop; parallel – separate branches, each works independently.
• Heating effect of current: Current produces heat in conductors, used in devices like irons and heaters.
• Fuse and safety: Fuse melts when current is too high, protecting appliances; we must follow safety rules while using electricity.

If you revise and understand these points well, you will be able to answer most questions from this chapter in your examination.