case study questions for class 7 science chapter 14

Gurukul of Excellence

Classes for Physics, Chemistry and Mathematics by IITians

Join our Telegram Channel for Free PDF Download

Case Study Questions for Class 7 Science Chapter 14 Electric Current and Its Effects

• Last modified on: 1 year ago
• Reading Time: 6 Minutes

[Download] Case Study Questions for Class 7 Science Chapter 14 Electric Current and Its Effects

Here we are providing case study or passage-based questions for class 7 science chapter 14 Electric Current and Its Effects.

Case Study/Passage Based Questions

We use various appliances based on heating effect of current in our daily life. Some such appliances are electric room heater, electric heater, hot plates, electric iron, hair dryers etc. All these contain a coil of wire called element.

• The coil of wire in an electric bulb is known as (a) element (b) filament (c) conducting wire (d) None of these
• Which part of an electrical iron becomes hot and gives out heat? (a) the switch (b) the handle (c) the element (d) the connecting wire
• The amount of heat produced depends upon which of the following? (a) material of element (b) length of wire (c) thickness of wire (d) All of these

Related Posts

What is case study question for class 7 science.

Case study or passage-based questions in class 7 Science typically require students to read a given scenario or passage and answer questions based on the information provided. These questions assess students’ comprehension, analytical thinking, and application of scientific concepts. 

Best Ways to Prepare for Case Study Questions

To develop a strong command on class 6 Science case study questions, you can follow these steps:

• Read the textbook and study materials:  Familiarize yourself with the concepts and topics covered in your class 6 Science curriculum. Read the textbook thoroughly and take notes on important information.
• Practice analyzing case studies:  Look for case studies or passages related to class 6 Science topics. Analyze the given information, identify key details, and understand the context of the situation.
• Develop comprehension skills:  Focus on improving your reading comprehension skills. Practice reading passages or articles and try to summarize the main points or extract relevant information. Pay attention to details, vocabulary, and the overall structure of the passage.
• Understand scientific concepts:  Ensure that you have a solid understanding of the scientific concepts discussed in class. Review the fundamental principles and theories related to each topic.
• Make connections:  Try to connect the information provided in the case study to the concepts you have learned in class. Identify any cause-effect relationships, patterns, or relevant scientific principles that apply to the situation.
• Practice critical thinking:  Develop your critical thinking skills by analyzing and evaluating the information given in the case study. Think logically, consider multiple perspectives, and draw conclusions based on the evidence provided.
• Solve practice questions:  Look for practice questions or sample case study questions specifically designed for class 6 Science. Solve these questions to apply your knowledge, practice your analytical skills, and familiarize yourself with the format of case study questions.
• Seek clarification:  If you come across any challenging concepts or have doubts, don’t hesitate to ask your teacher for clarification. Understanding the underlying principles will help you tackle case study questions effectively.

Download Books – Exam Special

Sample Papers for CBSE 2025 Exams

• Sample Question Papers for CBSE Class 8 All Subjects (for 2025 Exams)
• Sample Question Papers for CBSE Class 9 All Subjects (for 2025 Exams)
• Sample Question Papers for CBSE Class 10 All Subjects (for 2025 Exams)
• Sample Question Papers for CBSE Class 12 All Subjects (for 2025 Exams)

CBSE Class 10 Most Downloaded Books

• CBSE Important Numerical Problems Class 10 Physics Board Exams
• CBSE Practical Based Questions for Class 10 Science Board Exams
• CBSE Important Diagram Based Questions Class 10 Physics Board Exams
• CBSE Most Repeated Questions for Class 10 Science Board Exams

CBSE Class 12 Most Downloaded Books

• CBSE Important Diagrams & Graphs Asked in Board Exams Class 12 Physics
• CBSE Important Numericals Class 12 Physics Board Exams
• CBSE Important Laws & Principles Class 12 Physics Board Exams
• CBSE Important Definitions Class 12 Physics Board Exams
• Master Organic Conversions CBSE Class 12 Chemistry Board Exams
• CBSE Class 12 Physics Chapterwise Important Questions

CBSE Class 8 Most Downloaded Books

• Worksheets for CBSE Class 8 Maths – Chapterwise

ICSE Class 10

• ICSE Important Numericals Class 10 Physics BOARD Exams (215 Numericals)
• ICSE Important Figure Based Questions Class 10 Physics BOARD Exams (230 Questions)
• ICSE Mole Concept and Stoichiometry Numericals Class 10 Chemistry (65 Numericals)
• ICSE Reasoning Based Questions Class 10 Chemistry BOARD Exams (150 Qs)
• ICSE Important Functions and Locations Based Questions Class 10 Biology
• ICSE Reasoning Based Questions Class 10 Biology BOARD Exams (100 Qs)
• ICSE Reasoning Based Questions Class 10 Geography BOARD Exams
• ICSE Revision Notes for Class 10 Chemistry BOARD Exams
• ICSE Revision Notes for Class 10 Physics BOARD Exams

ICSE Class 9

• ICSE Important Figure Based Questions Class 9 Physics Exams
• ICSE Important Numerical Problems for Class 9 Physics Exams
• ICSE Reasoning Based Questions Class 9 Geography BOARD Exams (150 Qs)

CBSE Chapter-Wise Test Papers

• CBSE Class 9 Science Chapterwise Test Papers
• CBSE Class 10 Science Chapterwise Test Papers
• CBSE Class 10 Maths Chapterwise Test Papers
• CBSE Class 10 Social Science Chapterwise Test Papers
• CBSE Class 12 Physics Chapterwise Test Papers
• CBSE Class 12 Chemistry Chapterwise Test papers

✨ Join our Online NEET Test Series for 499/- Only for 1 Year

1 thought on “ Case Study Questions for Class 7 Science Chapter 14 Electric Current and Its Effects ”

• Pingback: Case Study Questions for CBSE Class 7 Science - Success Router

Leave a Reply Cancel reply

Editable Study Materials for Your Institute - CBSE, ICSE, State Boards (Maharashtra & Karnataka), JEE, NEET, FOUNDATION, OLYMPIADS, PPTs

Discover more from Gurukul of Excellence

Subscribe now to keep reading and get access to the full archive.

Type your email…

Continue reading

A to Z Classes

Cbse, ncert and icse solution online, class 7 science case study question, case study question class 7 science (cbse / ncert board).

Class 7 Science Case Study Question and Answer: CBSE / NCERT Board Class 7 Science Case Study Question prepared by expert Science Teacher. Students can learn Case Based Question / Paragraph Type Question for NCERT Class 7 Science.

There are total 18 chapter Nutrition in Plants, Nutrition in Animals, Fibre to Fabric, Heat, Acids, Bases and Salts, Physical and Chemical Changes, Weather, Climate and Adaptations of Animals to Climate, Winds, Storms and Cyclones, Soil, Respiration in Organisms, Transportation in Animals and Plants, Reproduction in Plants, Motion and Time, Electric Current and Its Effects, Light, Water: A Precious Resource, Forests: Our Lifeline, Wastewater Story

For any problem during learning any Case or any doubts please comment us. We are always ready to help You.

CBSE Class 7 Science Case Study Question

• Chapter 1 Nutrition in Plants Case Study Question
• Chapter 2 Nutrition in Animals Case Study Question
• Chapter 3 Fibre to Fabric Case Study Question
• Chapter 4 Heat Case Study Question
• Chapter 5 Acids, Bases and Salts Case Study Question
• Chapter 6 Physical and Chemical Changes Case Study Question
• Chapter 7 Weather, Climate and Adaptations of Animals to Climate Case Study Question
• Chapter 8 Winds, Storms and Cyclones Case Study Question
• Chapter 9 Soil Case Study Question
• Chapter 10 Respiration in Organisms Case Study Question
• Chapter 11 Transportation in Animals and Plants Case Study Question
• Chapter 12 Reproduction in Plants Case Study Question
• Chapter 13 Motion and Time Case Study Question
• Chapter 14 Electric Current and Its Effects
• Chapter 15 Light
• Chapter 16 Water: A Precious Resource
• Chapter 17 Forests: Our Lifeline
• Chapter 18 Wastewater Story

What is Case Study Question?

Ans. At case Study there will one paragraph and on the basis of that concept some question will made. Students have to solve that question.

How many marks will have at case based question?

Most of time 5 questions will made from each case. There will 1 or 2 marks for each question.

Important links:

• Lakhmir Singh Class 7 Solution
• NCERT Class 7 Math Solution

Copyright © 2024 | WordPress Theme by MH Themes

• NCERT Exemplar
• NCERT Exemplar Class 7
• Class 7 Science
• Chapter 14 Electric Current And Its Effects

NCERT Exemplar Solutions Class 7 Science Chapter 14 Electric Current and Its Effects

NCERT Exemplar Solutions for Class 7 Science Chapter 14 Electric Current and Its Effects include solutions to all the problems provided in the NCERT Exemplar book. These solutions provide answers to questions of varying difficulty, which will help you to gain in-depth knowledge on the topic, Electric Current and Its Effects.

NCERT Exemplar Solutions for Class 7 Science has questions, such as fill in the blanks, match the following, questions on electronic circuit diagrams, true or false questions, multiple-choice questions with their answers and detailed explanations.

NCERT Exemplar Solutions provided here have answers and explanations to 5 multiple-choice questions, answers to 7 very short answer questions, 4 short answer questions and 4 long answer questions.

Download the PDF of NCERT Exemplar Solutions for Class 7 Science Chapter 14 – Electric Current and Its Effects

Importance of NCERT Exemplar Solutions for Class 7 Science Chapter 14 Electric Current and Its Effects.

These exemplar solutions cover questions on the basics of electric circuits, heating and magnetic effect of electric current, symbols used in electric circuits, working of bulb filaments, fuse and MCB’S, applications of the magnetic effect of electric current, and working of an electric bell.

Topics Covered in NCERT Exemplar Solutions for Class 7 Science Chapter 14 Electric Current and Its Effects.

14.1 – Symbols of Electric Components

14.2 – Heating Effect of Electric Current

14.3 – Magnetic Effect of Electric Current

14.4 – Electromagnet

14.5 – Electric Bell

Access Answers to NCERT Exemplar Solutions for Class 7 Science Chapter 14 – Electric Current and Its Effects

Multiple-choice questions.

1. When an electric current flows through a copper wire AB as shown in Figure 14.1, the wire

(a) deflects a magnetic needle placed near it.

(b) becomes red hot.

(c) gives an electric shock.

(d) behaves like a fuse.

The answer is (a) deflects a magnetic needle placed near it.

Explanation:

A current-carrying wire acts as a magnet with a magnetic field around it, the strength of which depends upon the amount of current passing through it.

2. Choose the statement which is not correct in the case of an electric fuse.

(a) Fuses are inserted in electric circuits of all buildings.

(b) There is a maximum limit on the current which can safely flow through the electric circuits.

(c) There is a minimum limit on the current which can safely flow in the electric circuits.

(d) If a proper fuse is inserted in a circuit, it will blow off if current exceeds the safe limit.

The answer is (c) There is a minimum limit on the current which can safely flow in the electric circuits.

In the case of an electric fuse, there is only a maximum limit on the current which can safely flow in the electric circuits.

3. Three bulbs A, B, C are connected in a circuit, as shown in Figure 14.2. When the switch is ‘ON’

(a) bulb C will glow first.

(b) bulb B and C will glow simultaneously, and bulb A will glow after some time.

(c) all the bulbs A, B and C will glow at the same time.

(d) the bulbs will glow in the order A, B and C.

The answer is (c) all the bulbs A, B and C will glow at the same time.

All the bulbs will glow simultaneously as there is no lag time in the flow of current through the circuit.

4. When a switch is in OFF position,

(i) circuit starting from the positive terminal of the cell stops at the switch.

(ii) the circuit is open.

(iii) no current flows through it.

(iv) current flows after some time. Choose the combination of the correct answer from the following.

(a) all are correct

(b) (ii) and (iii) are correct

(c) only (iv) is correct

(d) only (i) and (ii) are correct

Answer is (b) (ii) and (iii) are correct

When the switch is off, the circuit will be incomplete hence it is open and no current flows through it.

5. Which of the following precautions need not be taken while using electric gadgets/appliances/circuits?

(a) We should never touch a lighted electric bulb connected to the mains.

(b) We should never experiment with the electric supply from the mains or a generator or an inverter.

(c) We should never use just any wire or strip of metal in place of a fuse.

(d) We should never turn the switch in ON position.

The answer is (d) We should never turn the switch in ON position.

To use electric gadgets/appliances/circuit switch should be turned on, hence statement d) is wrong.

Very Short Answer Questions

6. Which property of a conducting wire is utilised in making an electric fuse?

The low melting point of the wire is utilized in making an electric fuse.

7. Name the device used these days in place of electric fuses in electrical circuits.

Miniature Circuit Breaker (MCB).

8. Fill in the blanks:

(i) Our body is a ________________ of electricity.

(ii) An electric cell produces electricity from the __________ ___________ in it.

(iii) In an electric circuit, a fuse is a _________ _______ to prevent possible fire.

(iv) A combination of two or more cells is called a _________.

(i) Our body is a conductor of electricity.

(ii) An electric cell produces electricity from the Chemicals stored in it.

(iii) In an electric circuit, a fuse is a Safety device to prevent a possible fire.

(iv) A combination of two or more cells is called a battery .

9. Unscramble the following words:

(i) TBTAYER

(iii) HTRCO

(iv) HICWTS

10. Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel in the night to get dim light. Has she taken the right step? Give one reason to justify your answer.

No, the steps taken by Paheli are wrong as the towel may get burned due to heat produced by the bulb and also, glowing the bulb unnecessarily will waste energy.

11. Why are compact fluorescent lamps (CFLs) preferred over electric bulbs?

Compact fluorescent lamps (CFLs) are preferred over electric bulbs because CFLs consume less energy, and they will not waste energy in the form of heat.

12. Why is an electric fuse required in all electrical appliances?

An electric fuse is required because it acts as a safety device and it checks excessive current flow.

Short Answer Questions

13. Can we use the same fuse in a geyser and a television set? Explain.

No, we cannot use the same fuse in a geyser and television because a geyser and a television set require a different amount of current. Therefore the fuse used in these will be of different ratings.

14. Name two electric devices for each, where (i) the heating effect of current is used and (ii) the magnetic effect of current is used.

Heating effect – Geyser, room heater.

Magnetic effect – Electric bell, Cranes to lift magnetic material.

15. Why do we cover plug pinholes which are within reach of children with cello tape or a plastic cover when not in use?

Because the child may put his/her fingers into the socket, which results in electric shock, which may be fatal.

16. Boojho made an electromagnet by winding 50 turns of wire over an iron screw. Paheli also made an electromagnet by winding 100 turns over a similar iron screw. Which electromagnet will attract more pins? Give reason.

Paheli’s electromagnet will attract more pins as it has more number of turns of wire on it and thus a stronger electromagnet.

Long Answer Questions

17. Your teacher has shown you the following activity.

Activity: Teacher has wound a long insulated piece of wire around an iron nail in the form of a coil. Free ends of the wire are connected to a cell through a switch, as shown in Figure 14.3. The current is switched on and some pins are placed near the ends of the nail.

Write down any three questions that come to your mind about this activity.

(i) Why does the nail attract the pins?

(ii) What will happen if we connect more cells in the circuit?

(iii) What will happen if we use some other material like a straw in place of the nail?

(iv) What will happen if we wrap the wire on the nail more tightly?

18. Paheli took a wire of length 10 cm. Boojho took a wire of 5 cm of the same material and thickness. Both of them connected the wires, as shown in the circuit given in Figure 14.4. The current flowing in both circuits is the same.

• Will the heat produced in both the cases be equal? Explain.
• Will, the heat produced be the same if the wires taken by them are of equal lengths but of different thicknesses? Explain.

i) No, the amount of heat produced in both the cases will not be equal because the length of the wire decides the amount of heat produced in a wire

(ii) No, the thickness of the wire decides the amount of heat produced by the wire.

19. How does the magnetic effect of electric current help in the working of an electric bell? Explain with the help of a diagram.

An electric bell consists of a coil of wire wound on an iron piece. The coil acts as an electromagnet. An iron strip with a hammer at one end is kept close to the electromagnet. There is a contact screw near the iron strip. When the iron strip is in contact with the screw, the current flows through the coil, which becomes an electromagnet. It, then, pulls the iron strip. In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound.

20. Draw the symbols of the following circuit components.

(i) electric cell

(ii) switch in off position

(iii) electric bulb

(iv) battery

BYJU’S presents study materials, such as NCERT Solutions , NCERT Exemplars, sample papers, previous years’ question papers, videos and animations etc., to help students excel in their Class 7 examination as well as entrance examinations. To get access to the study materials of all the classes and subjects, Download BYJU’S – The Learning App.

Frequently Asked Questions NCERT Exemplar for Class 7 Science Chapter 14 Electric Current and Its Effects

Which property of a conducting wire is utilised in making an electric fuse.

The low melting point of the wire is utilised in making an electric fuse.

Name the device used these days in place of electric fuses in electrical circuits.

Paheli does not have a night lamp in her room. she covered the bulb of her room with a towel in the night to get dim light. has she taken the right step give one reason to justify your answer..

No, the steps taken by Paheli are wrong as the towel may get burnt due to heat produced by the bulb and also, glowing the bulb unnecessarily will waste energy.

Why are compact fluorescent lamps (CFLs) preferred over electric bulbs?

Compact fluorescent lamps (CFLs) are preferred over electric bulbs because CFLs consume less energy and they will not waste energy in the form of heat.

Why is an electric fuse required in all electrical appliances?

Can we use the same fuse in a geyser and a television set explain..

No, we cannot use the same fuse in a geyser and television because a geyser and a television set require a different amount of current. Therefore, the fuse used in these will be of different ratings.

Name two electric devices for each, where (i) the heating effect of current is used, and (ii) the magnetic effect of current is used.

Why do we cover plug pinholes which are within reach of children with cello tape or a plastic cover when not in use.

Because the children may put their fingers into the socket, which results in electric shock, which may be fatal.

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Request OTP on Voice Call

Post My Comment

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Electric Current and Its Effects Important Questions Class 7 Science Chapter 14

Electric Current and Its Effects Class 7 Science Chapter 14 Important Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 7 Science Book. These important questions will help you to properly understand a particular concept of the chapter. Practicing class 7 important questions before the exam will help you to get excellent marks in the exam. 

Class 7 Science Chapter 14 Electric Current and Its Effects Important Questions

Very short answer type question.

1: Circuit diagram is a simplified conventional pictorial representation of an_______________.

Answer:   electrical circuit

2: A circuit diagram uses standard symbols for electric components. True/ False.

Answer:   True.

3: Define electric circuit.

Answer:   A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit.

4: For a bulb to glow, it must be connected to a battery. Why?

Answer:   because a bulb will require more power

5: What is a cell holder?

Answer:   A compartment that holds two or more cells together to form a battery is called a cell holder.

6: A circuit is said to be open circuit or complete when current flows through it. True/ False.

Answer:   False

7: What is a battery?

Answer:   A combination of two or more cells connected together is called a battery.

8: Which one of the two minimise wastage of electricity CFL’s or an electric bulb?

Answer:   CFL’s

9: Electric room heaters have coils of wire that produce heat, which are known as heating elements. True/False.

Answer:   True

10: State some factors that affect production of heat in a wire through which an electric current is passing.

Answer:   Length and thickness of the wire, the duration of flow of current, and the material of the wire.

11: Name the principle of working of electric fuse.

Answer:   The electric fuse works on the principle of the heating effect of electric current.

12: What is an electric fuse?

Answer:   An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it.

13: What is the full form of MCB?

Answer:   Miniature Circuit Breaker.

14: What is the full form of CFL’s?

Answer:   Compact Fluorescent Lamps

15: State one advantage of MCB.

Answer:   These switches turn off automatically when there is an overload or a short circuit.

16: An electromagnet does not attract a piece of iron.

17: When current is switched ‘on’ in a room heater, it_________________.

Answer:   gives out heat

18: Name a safety device in domestic circuit used to prevent electrical fire due to short circuit or overloading.

Answer:   Electric fuse.

19: Enlist some appliances that work on the property of the magnetic effect of electric current.

Answer:   Electric Bell, Motor, Fan etc.

20: What is meant by electric current?

Answer:   Electric Current: Flow of electrons.

21: What is an electric circuit?

Answer:   Electric Circuit : The closed path in which electric current flows

22: What happens when current is switched ‘on’ in a room heater?

Answer:   It becomes red hot and gives out heat

23: Which of the two absorbs more radiation- a dark coloured object or a light coloured object?

Answer:   A dark coloured object will absorb more radiation.

24: Would any of the bulbs glow when the switch is in the ‘OFF’ position in a circuit?

Answer:   No, the bulbs will not glow.

25: What is a circuit diagram?

Answer:   In an electrical Circuit when we replace electrical components with their symbols we call it Circuit diagram.

26: When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. True/False

27: The combination of two or more cells is called a __________________.

Answer:   Battery

28: A straight wire carrying electric current is moving out of plane of paper and is perpendicular to it. What is the direction and type of induced magnetic field?

Answer:   Induced magnetic field will be in the form of concentric circles in the plane of paper.

29: A current through a horizontal power line flows in north to south direction. What is the direction of magnetic field (i)at a point directly below it and (ii)at a point directly above it?

Answer:   (i) West to East (ii) East to West

30: What do you mean by electromagnetic induction?

Answer:   The process, due to which a changing magnetic field in a conductor induces a current in another conductor, is called electromagnetic induction.

31: How we can show that magnetic field exist around a wire carrying current?

Answer:   By using magnetic compass which, shows deflection.

32: How can a solenoid be used to magnetise a steel bar?

Answer:   By inserting the steel bar inside the solenoid and switching on electric current.

33: Give the factors that affect strength of magnetic field at a point due to a straight conductor carrying current.

Answer:   Magnitude of electric current, perpendicular distance between that point and conductor.

34: A fuse is connected with a live wire or with neutral wire?

Answer:   Fuse is always connected with live wire.

Short Answer Type Questions

1: Differentiate between electric current and electric circuit.

Answer:   Electric Current is the flow of electrons. But an electric Circuit is the closed path in which electric current flows.

2: Explain the function of cell in a circuit.

Answer:   A cell supplies electric current. The positive terminal (+)of a cell is represented by a vertical long line, while the negative terminal (-) is shown as a parallel, shorter line.

3: How fuses are useful?

Answer:   A fuse is thus a safety device which prevents damages to electrical circuits and possible fires.

4: Can we use an electromagnet separating plastic bags from a garbage heap? Explain.

Answer:   An electromagnet cannot be used for separating plastic bags from a garbage heap as it attracts only iron pieces and will not attract plastic bags.

5: Write short notes on heating effects of electric current.

Answer:   When an electric current flows through a wire, the wire gets heated. It is the heating effect of current or When current flows through a metal wire it gets heated up, this is called heating effect of current. E.g. a glowing electric bulb becomes warm. This effect has many applications like Electric Heater, Light Bulb etc.

6: Write short notes on magnetic effects of electric current

Answer:  When an electric current flows through a wire, it produces magnetic effect around it. A current carrying coil of an insulated wire wrapped around a piece of iron is called an electromagnet. Magnetic Effect of electric current has many applications like Electric Bell, Motor, Fan etc

7: What are filaments of a bulb and a heater made up of?

Answer:   In a bulb there is a thin wire called the filament made up of tungsten. When current passes through it, it glows and gets heated up. In a heater there is a coil of wire called element which is made up of nichrome. When current passes through element it becomes red hot and give out heat

8: Why does electric current show magnetic effect?

Answer:   When electric current flows through a conductor, electrons move by spinning and orbiting nucleus. This motion of electrons produces magnetic effect. As Ampere suggested, a magnetic field is produced whenever an electrical charge is in motion.

9: Why are fuse wire not used in circuit containing electric cell?

Answer:   Fuse wire is used to prevent sudden excess flow of current. Cell provide current of fix magnitude So fuse wire are not used in circuit containing electric cell

10: Why does electric current show heating effect?

Answer:   When electric current flows through a conductor, a part of electrical energy get converted into heat energy due resistance offered to electron.

11: What is magnetic field?

Answer:   The region around the magnet, where force of attraction or repulsion can be felt by magnetic materials, is called as magnetic field.

12: What are the patterns of magnetic field lines inside and outside of a solenoid?

Answer:   Following are the patterns of magnetic field lines inside and outside of a solenoid

• The field lines inside the solenoid are parallel straight lines
• The field lines outside the solenoid are curved lines

13: State the principle of working of electric generator. What are its important parts?

Answer:   The working of electric generator is based on the principle of electromagnetic induction. The Important parts of electric generator are armature, slip rings, brushes and field magnets.

14: Two magnetic lines of force don’t intersect each other. Explain why?

Answer:   If two magnetic lines of force will intersect each other then, at the point of intersection there will be two different directions of magnetic field which is not possible.

15: Give two methods by which we can increase the strength of magnetic field produced by a circular coil carrying current?

Answer:  The two methods by which we can increase the strength of magnetic field are as follow

• By increasing the number of turns of wire in the coil.
• By increasing the current flowing through the coil.

16: The patterns of magnetic field lines inside a solenoid are parallel straight lines. What does this indicate?

Answer:   The field lines inside the solenoid are parallel straight lines. This indicates that the magnetic field is uniform and is therefore, same at all points inside it.

17: The patterns of magnetic field lines outside a solenoid are parallel curved lines. What does this indicate?

Answer:   The field lines outside the solenoid are curved lines. This indicates that the magnetic field is non-uniform.

18: State the factors on which the force experienced by a current carrying conductor placed in a uniform magnetic field depends upon?

Answer: The factors which govern the force experienced by conductor which is placed in a uniform magnetic field are:

• Strength of the magnetic field in which conductor is placed.
• Strength of current flowing through the conductor.
• Length of conductor

18: Write short notes on Overloading.

Answer:   Overloading occurs in a circuit when the current in the circuit increases abruptly. It causes overheating of the wire and might lead to the fire. It can also occur due to accidental increase in the supply voltage or on connecting too many appliances to a single socket.

19: It is established that an electric current through a metallic conductor produces a magnetic field around it. Is there a similar magnetic field produced around a thin beam of moving (i) alpha particles, (ii) neutrons? Justify your answer.

Answer: (i) Yes, Alpha particles being positively charged constitute a current in the direction of motion. 

(ii) No. The neutrons being electrically neutral constitute no current.

Long Answer Type Questions

1: Explain the formation and uses of battery.

Answer:   A combination of two or more cells connected together is called a battery. It supplies electric current. It is formed by connecting the positive terminal of one cell to the negative terminal of another. To identify the positive and negative terminals, they are denoted as + and –, respectively. These batteries are used in many devices, such as torch lights, mobile phones, calculators and even automobiles.

2: An electrician is carrying out some repairs in a building. He wants to replace a fuse by a piece of wire. Would you agree with the electrician? Give reasons for your response.

Answer:   There is a maximum limit on the current which can safely flow through a circuit. If by accident the current exceeds this safe limit, the wires may become overheated and may cause fire. In order to prevent this, in all buildings fuses are inserted in all electrical circuits. If a proper fuse is there in the circuit, it will blow off and break the circuit. A fuse is thus a safety device which prevents damages to electrical circuits and possible fires. So we will not agree with an electrician, who is using a wire in place of fuse of proper rating as if by accident the current exceeds safe limit, the wires may become overheated and may cause fire.

3: Look at the figure given below and answer whether the compass needle will show deflection or not when the switch in the circuit shown is closed? 

Answer:   The compass needle will not show any deflection when the switch in the circuit shown by above figure is closed, because there is no power source like cells in the circuit hence there will be no electric current flow in the circuit. In the absence of electric current there will be no magnetic effect to cause the deflection of compass needle.

4: When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Answer:   As we know that the needle of a compass is a tiny magnet, which points in north-south direction. When we bring a magnet close to it, the needle gets deflected. Also, when an electric current flows through a wire, it produces magnetic effect around it. Therefore, when the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position due to magnetic effect of electric current around the wire.

5: State the factors on which amount of heat produced depends?

Answer:   The amount of heat produced in a wire depends on 

(A) Its material – better conductors produce less heat; e.g. Elements of electric appliances are made of nichrome whereas connecting wires are made up of copper which is a better conductor so they do not get heated up as the element. 

(B) Its length – as length increases heat produced increases; e.g. elements are coiled in heaters to increase length. 

(C) Thickness – as thickness increases heat produced decreases; e.g. lead wires of iron, heater etc. are thicker than normal connecting wire so that they don’t get heated up easily

6: Why mostly all electrical home appliances like refrigerator, toaster etc. are provided with a wire having green insulation?

Answer:   Earth wire is the insulated green coloured copper wire which is connected to a metal plate deep inside the earth near the house. It is used as a safety measure. It is kept at zero potential by connecting it to the ground, thus, providing a low-resistance conducting path for the current. 

When by electric fault, if current flows through the metallic body of electric appliance and we touch it, then current finds the lower resistance path of earth wire than our body. So, current flows through earth wire only and we remain safe.

7: Write short notes on Short Circuiting.

Answer:   Short-circuiting occurs in a circuit when the live wire comes in direct contact with the neutral wire. This causes much damage to the electric appliances connected with them. Reason of short-circuiting: When the live wire touches the neutral wire, the contact portion of the two wires behave like load and due to very low resistance of copper wire, it draws very large amount of current. In the presence of this high current, the copper wire catches fire, due to joules heating effect.

8: Mention the differences between an electromagnet and a permanent magnet. Answer: 

9: What are the properties of magnetic field due to a current through a straight wire?

Answer:   The properties of magnetic field due to a current flowing through a straight wire are:

• The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.
• The magnetic field produced by a given current in the conductor decreases as the distance from it increases.
• The concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it.
• If the direction of the current is reversed in the wire, the lines will still be circular, but the directions of the lines will be reversed, which can be verified using the compass needle.

10: State few characteristics of magnetic field lines.

Answer:   Following are the characteristics of magnetic field line:

• They represent the magnetic field.
• They are directed from north to South Pole outside a magnet and from south to North Pole inside a magnet.
• The field lines are closed curves.
• The strength of magnetic field in a region is determined by closeness of the field lines in that region.
• The closer the field lines are, greater will be the field strength and vice–versa.
• No two field lines ever cross each other as it would mean two different directions of field at point of intersection, which is not possible.
• The parallel lines represent the uniform magnetic field whereas converging lines or diverging lines represents the non-uniform magnetic field.