These Class 8 Science Curiosity Worksheet and Class 8 Science Chapter 4 Electricity: Magnetic and Heating Effects Worksheet with Answers are excellent for board exam practice.
Class 8 Science Chapter 4 Electricity: Magnetic and Heating Effects Worksheet
Class 8 Electricity: Magnetic and Heating Effects Worksheet
Worksheet On Electricity: Magnetic and Heating Effects Class 8 – Electricity: Magnetic and Heating Effects Worksheet Class 8
Let’s Begin
A. Multiple-Choice Questions
Question 1.
The region around a magnet where its magnetic effect can be felt is known as
(a) Magnetic field
(b) Electric field
(c) Heating effect
(d) Electromagnet.
Question 2.
Which scientist discovered that electricity and magnetism are linked?
(a) Issac Newton
(b) Alessandro Volta
(c) Hans Christian Oersted
(d) Benjamin Franklin
Question 3.
Which of the following statements is true about a dry cell?
(a) It has an electrolyte of weak acid or salt solution.
(b) It can be used many times.
(c) It has a thick moist paste as the electrolyte.
(d) The carbon rod acts as the negative terminal.
Question 4.
This question consists of an Assertion (A) and a Reason (R). Read the Assertion and Reason and choose the appropriate answer.
Assertion (A): A cylindrical coil becomes a magnet when electric current passes through it.
Reason (R): A coil with an iron nail deflects a magnetic compass more.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Question 5.
This question consists of an Assertion (A) and a Reason (R). Read the Assertion and Reason and choose the appropriate answer.
Assertion (A): A Voltaic cell is also known as a dry cell.
Reason (R): In a Voltaic cell, copper acts as the positive electrode, and zinc as the negative electrode.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
B. State True (T) or False (F).
1. An incandescent lamp glows because an electric current heats its filament.
2. A nichrome wire offers higher resistance compared to a copper wire of the same size and length.
3. Rechargeable batteries cannot be recharged and reused multiple times.
4. Overheating in appliances does not cause any damage to plugs, sockets, or wiring.
5. The magnetic field of a lifting electromagnet disappears when the electric current is switched OFF.
C. Fill in the blanks.
1. The negative terminal of a dry cell is the ______ ro(d)
2. The compass needle returns to its original direction when the ______ stops.
3. Most electromagnets have an ______ core to make them stronger.
4. in an LED, longer wire is connected to the ______ terminal of the battery.
5. In steel industries, a high-temperature ______ uses electric current to produce heat.
D. Assign one word to the following terms.
1. Material that allows the flow of electricity. ______
2. Current carrying coil that behaves like a magnet. ______
3. Tool used to detect magnetic deflection. ______
4. Property that opposes the flow of current. ______
5. Device that produces electric current through chemical reactions. ______
E. Match the Columns.
Question 1.
Match the terms given in Column I with their correct descriptions given in Column II.
| Column I | Column II |
| (i) Magnetic compass | (a) Strength can be changed by changing the amount of flowing current. |
| (ii) Lifting electromagnets | (b) Acts as a shield by blocking harmful particles. |
| (iii) Electromagnet | (c) Used to find directions. |
| (iv) Earth’s magnetic field | (d) Used in factories and scrap yards to sort heavy metal items. |
Question 2.
Match the pictures given in Column I with their correct descriptions given in Column II.
Wonder Why?
A. Give reasons for the following.
Question 1.
Imagine you place a compass near a wire carrying an electric current. Why does the compass needle change its direction when the wire is carrying current, but stays steady when there is no current?
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Question 2.
How did Hans Christian Oersted’s observation of a deflected compass needle lead to the discovery that electricity and magnetism are linked?
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Question 3.
Why does a current carrying coil act like a magnet, and why does inserting an iron nail in the core of a coil make it stronger?
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Question 4.
Why does a nichrome wire become warm when an electric current passes through it, and why does it heat up more when the current is stronger?
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Question 5.
How does switching the current ON and OFF help in controlling a lifting electromagnet? How are they used in factories and scrap yards?
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B. Observe the following set-ups with a wire coil, a battery, a magnetic compass, an iron nail, and some paper clips and complete the table with your predictions and observations.
C. Read each statement carefully. Decide if it is correct or incorrect. If it is incorrect, rewrite it correctly ¡n the space provided.
| Statement | Corrector or Incorrect? | Rewrite (if incorrect) |
| 1. When electric current flows through a coil, it cannot produce magnetism. | ||
| 2. A compass needle placed near a current-carrying coil shows deflection. | ||
| 3. An electromagnet has no poles unless it touches a permanent magnet. | ||
| 4. If the north pole of the compass is attracted towards coil end A, end A is the south pole. | ||
| 5. Both ends of the coil have the same polarity when current flows through it. | ||
| 6. Removing the battery breaks the magnetic field around the coil. | ||
| 7. Reversing the current in the coil changes its magnetic poles. |
D. Switch the electric current ON and OFF in the electromagnet circuit as shown in the diagram. Record your observations of how effectively the e1ectrornan lifts iron objects.
1. With current switched OFF
2. With current switched ON
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Learn By Doing
A. Mount a 12 cm, 0.4 mm nichrome wire between two nails on cardboard. Connect it to a cell, switch, and holder. Touch the wire before switching ON. Then switch it ON and allow current to pass for 30 seconds. Switch OFF the current and touch the wire again. Observe temperature change. Write your conclusion with reasons about heating due to the current flow in the given space.
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B. Draw a neat and labelled diagram of a dry cell.
C. Take 5-6 lemons, copper wires, and iron nails. Insert one copper wire and one nail in each lemon. Connect them in series and attach an LED between the first copper wire and last nail. Observe the LED. Reverse connections if neede(d) Write an observation and a conclusion in the given space.
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Explore With Curiosity
A. Read the paragraph and answer the following questions. Understanding/Analyse
Dry cells are commonly used electric cells where the electrolyte is a thick, moist paste instead of a liqui(d) These cells are single-use and must be disposed of after use. Rechargeable batteries, on the other hand, can be recharged and reused multiple times. However, these batteries also wear out after several charge-discharge cycles.
Question 1.
Why are dry cells called dry’?
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Question 2.
Which parts of a dry cell act as positive and negative terminals?
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Question 3.
How do rechargeable batteries help in reducing wastage?
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Question 4.
Name four devices that commonly use rechargeable batteries.
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Question 5.
Why do rechargeable batteries eventually stop working after some time?
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B. Read the conversation between Riya and Aman and answer the following questions.
Question 1.
What might be the reason that the coil in the heater starts to glow when it is switched on?
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Question 2.
Riya and Aman talk about irons and kettles becoming hot when in use. What do you think makes them heat up?
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Question 3.
Based on the conversation, what link can you find between the glowjng of a heater coil and the heating of appliances like irons or kettles?
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C. Observe the given Voltaic cell carefully and label it.
Now, answer the following questions.
Question 1.
What is the function of the electrolyte in a Voltaic cell?
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Question 2.
How is electricity produced in a Voltaic cell?
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Question 3.
What are the electrodes in a Voltaic cell made of?
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Question 4.
Who discovered Voltaic cell?
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Word Puzzle
Find the words in the word search puzzle with the help of clues given below.
1. The area around a magnet where, magnetic force can be felt. ______
2. A type of battery that can be used multiple times. ______
3. A type of cell that produces electricity through chemical reactions. ______
4. A current carrying coil that behaves as a magnet. ______
5. An object that attract materials like iron and steel toward itself. ______
6. An instrument used to find direction by using the Earth’s magnetic fiel(d). ______
7. A heating effect in electrical appliances that can cause damage to plugs and sockets. ______
8. The property of a magnet having two opposite poles. ______
Suggested Activities
A. Make coils with 15, 30, 60, and 90 turns of wire and connect each to the same cell. Place a magnetic compass in the same position near each coil and observe the needle deflection. Record your observations and conclude the effect of number of turns of coil on the strength of the electromagnet.
B. Take two nichrome wires of equal length but different thickness (about 0.5 mm and 1.0 mm). Connect each wire separately to a circuit with a cell and a switch and allow the current to flow for 30 seconds. Touch both wires and observe which heats up more. Repeat the experiment with wires of same thickness but different lengths and prepare a brief report on how the thickness and length of a wire affect its heating.
C. Try to make an electric cell using various fruits or vegetables with different metal electrodes. Record your observations and prepare a short report on which combinations work best.