Maharashtra Board Class 7 Science Chapter 19 Properties of a Magnetic Field Solutions

1. Write the appropriate terms in the blanks:

Question a. The alloys called .......... and .......... are used for making industrial magnets.
Answer: alnico, Nipermag
In simple words: Alnico and Nipermag are special metal mixtures that are strong magnets, commonly used in factories and various industrial tools. They are chosen for their ability to maintain magnetism.

🎯 Exam Tip: Remember the names of these alloys for industrial magnets, as they are key examples of magnetic materials.

Question b. A magnetic field can pass through ............ and ............ .
Answer: cardboard, bottle
In simple words: A magnetic field isn't stopped by everyday non-magnetic materials like cardboard or plastic bottles, meaning its force can extend through them.

🎯 Exam Tip: Understanding what materials magnetic fields can pass through helps explain how magnets work through obstacles.

Question c. The intensity of a magnetic field is indicated by the lines of ............ .
Answer: force
In simple words: The strength of a magnetic field is visually represented by magnetic lines of force; where these lines are denser, the field is stronger.

🎯 Exam Tip: Magnetic lines of force are a fundamental concept for visualizing and understanding magnetic field strength and direction.

Question d. The real test of a magnet is ............ .
Answer: repulsion
In simple words: While magnets can attract many things, the true way to confirm an object is a magnet is if it repels another known magnet, as only like poles of magnets repel each other.

🎯 Exam Tip: Repulsion is the definitive test for magnetism, distinguishing a magnet from a magnetic material that is simply attracted.

2. With whom should I pair up?

Question a.

Answer:

In simple words: This pairing exercise connects magnetic concepts: a compass uses a magnetic needle, a cupboard door often uses a magnet, repulsion occurs between like poles, and magnetic poles are where magnetic force is strongest.

🎯 Exam Tip: Memorize these fundamental pairings to quickly recall key definitions and applications of magnetism.

3. Write answers to the following questions:

Question a. Distinguish between the two methods of making artificial magnets
Answer:

In simple words: The single touch method uses one magnet to magnetize a steel bar, creating a weaker, temporary magnet, while the double touch method uses two magnets simultaneously, resulting in a stronger, more lasting artificial magnet.

🎯 Exam Tip: Focus on the number of magnets used, the direction of stroking, and the strength/duration of the resulting magnetism to differentiate these methods effectively.

Question b. Which substances are used for making electromagnets?
Answer: The substances used for making electromagnets are, an iron nail, insulated copper wire, one or more batteries and a pair of wire strippers.
In simple words: To make an electromagnet, you need an iron core (like a nail), insulated copper wire to coil around it, and a power source like batteries to pass electric current.

🎯 Exam Tip: Remember the core components- an iron core, a coil of wire, and a power source- as essential for constructing an electromagnet.

Question c. Write a note on magnetic field
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक बार चुंबक के चारों ओर चुंबकीय क्षेत्र की रेखाओं को दर्शाता है। ये बल रेखाएँ उत्तरी ध्रुव से निकलकर दक्षिणी ध्रुव में प्रवेश करती हैं और चुंबक के अंदर दक्षिणी ध्रुव से उत्तरी ध्रुव की ओर चलती हैं, एक बंद लूप बनाती हैं। ये रेखाएँ चुंबकीय क्षेत्र की दिशा और तीव्रता को दर्शाती हैं।
Answer: 1. The region around a magnet where the magnetic force acts on an object is called a magnetic field. 2. The magnetic field around a magnet can be shown by means of magnetic lines of force. 3. The intensity of the magnetic field can be obtained from the number of lines of force. 4. The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated. 5. A magnetic field is the magnetic effect of electric currents and magnetic materials. 6. The magnetic field at any given point is specified by both the direction and the magnitude. 7. Magnetic fields are produced by electric current.
In simple words: A magnetic field is the invisible area around a magnet where its force can be felt, visualized by lines of force that show both its strength (closer lines mean stronger field) and direction. It can be created by magnets or electric currents.

🎯 Exam Tip: Understand that magnetic fields have both direction and magnitude, can be represented by field lines, and are produced by magnets and electric currents.

Question d. Why is a magnetic needle used in a compass?
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक चुंबकीय सुई को एक कटोरे में तैरते हुए दिखाता है, जिसके किनारे पश्चिम (W) और पूर्व (E) दिशाओं को दर्शाते हैं। चुंबकीय सुई का 'S' (दक्षिण) सिरा पृथ्वी के चुंबकीय क्षेत्र के कारण एक विशिष्ट दिशा में संरेखित होता है, जो कम्पास के माध्यम से दिशा का पता लगाने में मदद करता है।
Answer: 1. The magnetic compass is the most familiar compass type. 2. It functions as a pointer to magnetic 'north' the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the earth's magnetic field. 3. A compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal direction.
In simple words: A magnetic needle is used in a compass because it's a small magnet that naturally aligns itself with Earth's magnetic field, allowing it to point towards the magnetic north and help with navigation.

🎯 Exam Tip: The key function of a compass needle is its alignment with Earth's magnetic field, which is crucial for navigation and direction finding.

Question e. Explain with the help of a diagram how the intensity and direction of the magnetic field of a bar magnet can be determined.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक बार चुंबक के चारों ओर चुंबकीय क्षेत्र की रेखाओं को दर्शाता है। बल रेखाएँ उत्तरी ध्रुव से निकलकर दक्षिणी ध्रुव में प्रवेश करती हैं, और चुंबक के अंदर दक्षिणी ध्रुव से उत्तरी ध्रुव की ओर चलती हैं। जहां रेखाएं सघन होती हैं, चुंबकीय क्षेत्र तीव्र होता है, और जहां वे विरल होती हैं, क्षेत्र कमजोर होता है।
Answer: 1. The region around a magnet where the magnetic force acts on an object is called a magnetic field. 2. The magnetic field around a magnet can be shown by means of magnetic lines of force. 3. The intensity of the magnetic field can be obtained from the number of lines of force. 4. The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated. 5. A magnetic field is the magnetic effect of electric currents and magnetic materials. 6. The magnetic field at any given point is specified by both the direction and the magnitude. 7. Magnetic fields are produced by electric current.
In simple words: The intensity and direction of a bar magnet's magnetic field are shown by magnetic lines of force; denser lines indicate higher intensity, and the lines flow from the north pole to the south pole externally.

🎯 Exam Tip: When explaining magnetic fields with a diagram, always highlight how the density of field lines correlates with field intensity and how the arrows on the lines indicate direction.

4. Give detailed information about how the merchants of olden times used a magnet while travelling.

Question a. Give detailed information about how the merchants of olden times used a magnet while travelling.
Answer: 1. The merchants of older times used a magnet whose north-south side was known. 2. When the magnet is freely suspended, the north pole of the magnet settles in the direction of the geographic north pole of the earth. 3. This is how the merchants come to know the directions while travelling. 4. The idea for using loadstone in a compass first appeared in China. 5. The first compass were made of loadstone, a naturally magnetised ore of iron. 6. The Chinese used "south pointing spoon" which when thrown upon the ground comes to rest pointing at the south. 7. Then the transition was made from loadstone spoons to iron needles. 8. In the medieval period a magnetic needle in the shape of a fish, floating in the bowl of water was used as a compass, pointing south. 9. It was called floating compass. 10. In the twentieth century, liquid filled magnetic compass began to appear. 11. There is a lesser known compass called dry mariners compass.
In simple words: Ancient merchants, particularly in China, used naturally magnetic stones (lodestone) or magnetic needles, often suspended or floated, which would align with Earth's magnetic field to determine directions for travel.

🎯 Exam Tip: Focus on the evolution from lodestone to magnetic needles and the principle of a freely suspended magnet aligning with Earth's magnetic north-south for historical navigation questions.

Project:

Question a. Obtain information about the function of metal detectors.
Answer: Metal detectors function by creating a changing magnetic field that induces electric currents in nearby metal objects. These induced currents, in turn, create their own magnetic fields, which are detected by the device, indicating the presence of metal.
In simple words: Metal detectors work by sending out a magnetic field and listening for changes that occur when that field interacts with metal objects, revealing their presence.

🎯 Exam Tip: For project-based questions, describe the core principle (electromagnetic induction) and common applications (security, treasure hunting) of metal detectors.

Write the appropriate terms in the blanks:

Question 1. The magnetic lines of force always run from the north pole to the ............ .
Answer: south pole
In simple words: Magnetic field lines always start from a magnet's north pole and end at its south pole, forming continuous loops.

🎯 Exam Tip: Remember this fundamental rule for magnetic field lines: North to South outside the magnet, and South to North inside.

Question 2. The unit of magnetic field strength is ............ .
Answer: A/M (Amperes per metre)
In simple words: The strength of a magnetic field is measured in units of Amperes per metre, indicating the intensity of the magnetic force.

🎯 Exam Tip: Be sure to know the standard units for physical quantities like magnetic field strength for multiple-choice questions.

Question 3. The earth behaves like a giant ............ .
Answer: barmagnet
In simple words: Earth acts like a massive bar magnet due to the molten iron in its core, creating a global magnetic field.

🎯 Exam Tip: The Earth's magnetic field is often analogized to a gigantic bar magnet, a crucial concept for understanding compasses and geomagnetism.

Question 4. The ............ properties of magnetic field was proposed by scientist
Answer: Michael Faraday
In simple words: Michael Faraday was the scientist who first conceptualized and described the idea of magnetic field lines, explaining how magnetic forces act.

🎯 Exam Tip: Associate Michael Faraday with the concept of magnetic field lines and the properties of magnetic fields.

Question 5. The region around a magnet where the magnetic force acts on an object is called the ............ .
Answer: magnetic field
In simple words: The space surrounding a magnet where its attractive or repulsive force can be experienced is known as its magnetic field.

🎯 Exam Tip: A clear understanding of the definition of a magnetic field is fundamental to the chapter.

Question 6. The ............ of the magnetic field can be obtained from the number of lines of force.
Answer: strength
In simple words: The number or density of magnetic lines of force indicates how strong the magnetic field is in a particular area.

🎯 Exam Tip: Remember that a greater concentration of magnetic lines of force directly implies a stronger magnetic field.

Question 7. The function of the metal detector is based on ............ .
Answer: electromagnets
In simple words: Metal detectors use the principles of electromagnets to create and detect magnetic fields, which helps them find hidden metal objects.

🎯 Exam Tip: Connect metal detectors directly to the concept of electromagnets and their ability to generate and sense magnetic fields.

Question 8. The magnetism is ............ in the case of an electromagnet.
Answer: temporary
In simple words: Unlike permanent magnets, an electromagnet's magnetism is temporary, as it only functions when electric current flows through its coil.

🎯 Exam Tip: A key characteristic of an electromagnet is its temporary magnetism, which can be turned on or off with electric current.

Match the following:

Question 1.

Answer:

In simple words: This matching set connects magnetic substances (iron, nickel, cobalt), types of magnets (electromagnet, permanent magnet), specific alloys (Alnico, Nipermag), and historical magnetic tools (lodestone, mariner's compass) to their correct descriptions.

🎯 Exam Tip: Focus on identifying the primary function or composition for each term in Column 'A' to correctly match it with Column 'B'.

Write True or False correct and rewrite the false statements:

Question 1. Material alnico is a mixture of aluminium, nickel and iron.
Answer: False. Alnico is an alloy of aluminium, nickel and cobalt
In simple words: The statement is false; Alnico is an alloy made of aluminum, nickel, and cobalt, not iron.

🎯 Exam Tip: Pay close attention to the exact components of alloys like Alnico, as a single incorrect element can make the statement false.

Question 2. Nipermag is alloy of iron, nickel, cobalt.
Answer: False. Nipermag is an alloy of iron, nickel, aluminium and titanium
In simple words: The statement is false; Nipermag is an alloy consisting of iron, nickel, aluminum, and titanium, not cobalt.

🎯 Exam Tip: Differentiate between the compositions of Alnico and Nipermag to avoid common errors in identifying their constituent metals.

Question 3. The magnetic force is concentrated at the centre of the magnet.
Answer: False. The magnetic force is concentrated at the poles of the magnet.
In simple words: The statement is false; a magnet's strength, and thus its magnetic force, is strongest at its poles (ends), not in the middle.

🎯 Exam Tip: Always remember that magnetic force is strongest at the poles and weakest at the center of a magnet.

Question 4. Magnetism of electromagnet is permanent.
Answer: False. Magnetism of electromagnet is temporary
In simple words: The statement is false; electromagnets only exhibit magnetism when an electric current is flowing, making their magnetism temporary.

🎯 Exam Tip: Understand that the key distinction of an electromagnet is its ability to turn magnetism on and off, making it temporary, unlike a permanent magnet.

Question 5. Like poles attract each other and unlike poles repel each other.
Answer: False. Like poles repel each other and unlike poles attract each other
In simple words: The statement is false; the fundamental rule of magnetism is that like poles (North-North or South-South) repel, while unlike poles (North-South) attract.

🎯 Exam Tip: This is a core principle of magnetism; always recall that "opposites attract" and "likes repel" for magnetic poles.

Question 6. Two poles of a magnet cannot be separated from each other.
Answer: True.
In simple words: The statement is true; if you cut a magnet in half, each new piece will instantly form its own north and south poles, demonstrating that poles cannot exist in isolation.

🎯 Exam Tip: A magnet always has both a north and a south pole; they cannot be isolated, regardless of how many times the magnet is broken.

Answer in one or two sentences:

Question 1. In which direction does a freely suspended magnet settle?
Answer: The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth. It settles in north-south direction.
In simple words: A freely suspended magnet always aligns itself in a North-South direction, with its north pole pointing towards the Earth's geographic north pole.

🎯 Exam Tip: Remember that a freely suspended magnet always points approximately North-South due to Earth's magnetic field.

Question 2. Write any two functions of metal detectors.
Answer: 1. Metal detectors are used in very important places like an airport, bus station, certain temples and buildings to inspect those who are entering these places. 2. To detect very precious articles.
In simple words: Metal detectors are primarily used for security screening at public places to detect hidden metal objects, and also for locating valuable metals or artifacts underground.

🎯 Exam Tip: Focus on the dual applications of metal detectors: security checks for safety and finding valuable items for discovery.

Question 3. Which magnetic poles attract each other?
Answer: Opposite magnetic poles attract each other.
In simple words: Only magnetic poles that are different from each other, like a north pole and a south pole, will attract.

🎯 Exam Tip: Reinforce the rule: "Opposite poles attract, like poles repel."

Question 4. What metals are used for making magnets?
Answer: 1. Magnets are made from alloys of iron, cobalt and nickel. 2. Nipermag is an alloy made up of iron, nickel, aluminium and titanium whereas alnico is an alloy made up of aluminium, nickel and cobalt.
In simple words: Magnets are typically made from alloys containing iron, cobalt, and nickel, with specific combinations like Nipermag (iron, nickel, aluminum, titanium) and Alnico (aluminum, nickel, cobalt) forming strong magnetic materials.

🎯 Exam Tip: Note that magnets are usually made from alloys, not pure metals, and remember the key ferromagnetic elements (iron, nickel, cobalt).

Give scientific reasons:

Question 1. Earth is called as a gigantic magnet.
Answer: 1. The earth is called as a gigantic magnet because north pole of a freely suspended magnet always settles in the direction of the geographic north pole of the earth. 2. It means that the South pole of some gigantic magnet must be near the geographic north pole of that magnet, near the geographic south pole of the earth. 3. Gilbert inferred from this that the earth itself is a gigantic magnet.
In simple words: Earth is considered a giant magnet because a freely suspended magnetic needle aligns with its magnetic field, implying a large magnetic source within, effectively a huge bar magnet.

🎯 Exam Tip: The evidence for Earth being a giant magnet comes from how compasses behave, aligning with a global magnetic field generated from its core.

Question 2. A bar magnet kept on the cardboard arranges the iron fillings in line.
Answer: 1. A bar magnet kept on the cardboard arranges the iron fillings in line because of the 'magnetic lines of force'. 2. These magnetic lines gauge the intensity of the bar magnet. 3. The intensity of the magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated. 4. Therefore, the iron fillings arrange themselves according to intensity of the magnetic lines of force.
In simple words: Iron filings align around a bar magnet on cardboard because they become temporarily magnetized and follow the invisible magnetic lines of force, showing where the field is strongest and weakest.

🎯 Exam Tip: This experiment demonstrates how iron filings reveal the pattern and varying intensity of magnetic field lines around a magnet.

Write short note on:

Question 1. Functions of metal detector.
Answer: 1. A metal detector is an electronic instrument which detects the presence of metals nearby. 2. The function of these machines is based on electromagnets. 3. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. 4. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects. 5. Metal detectors in the food manufacturing industry are used to detect and eliminate threats of metal contaminants in food. 6. Metal detectors are used in very important places like an airport, bus station, temples, hospitals, railway stations, theaters, malls. 7. They are used for inspection of persons entering these places. 8. In geology, these machines are used to detect the presence and quantity of metals.
In simple words: Metal detectors are electronic devices that use electromagnets to locate hidden metals, serving critical roles in security, industrial quality control, and geological exploration by identifying both visible and concealed metallic objects.

🎯 Exam Tip: When writing about metal detectors, ensure you mention their electromagnetic principle and diverse applications in security, industry, and treasure hunting.

Question 2. Write down the characteristics of magnets.
Answer: 1. A freely suspended magnet settles in the north- south direction always. 2. Magnets attract objects of iron, cobalt and nickel. 3. The force of attraction of a magnet is greater at its poles than in the middle. 4. Like poles of two magnets repel each other. 5. Opposite poles of two magnets attract each other. 6. If a bar magnet is suspended by a thread and if it is free to rotate its south pole will move towards the north pole of the earth.
In simple words: Magnets always have two poles where force is strongest, attract specific metals like iron, align North-South when free, and show attraction between unlike poles while repulsion between like poles.

🎯 Exam Tip: For characteristics, list the fundamental properties: polar strength, attractive force on specific metals, directional property, and interaction rules between poles.

Question 3. Characteristic of magnetic lines of force
Answer: 1. Magnetic lines of force start from the north pole and end at the south pole. 2. They are continuous through the body of magnet. These are imaginary lines. 3. Magnetic lines of force can pass through iron more easily than air 4. The number of magnetic lines force determines the strength of the magnetic field at a particular point. 5. Two magnetic lines of force do not intersect each other. 6. They contract longitudinally and expand laterally.
In simple words: Magnetic lines of force are imaginary lines that start from the north pole, end at the south pole, never cross each other, and their density indicates the magnetic field's strength.

🎯 Exam Tip: Focus on the rules of magnetic field lines: their origin/termination, non-intersection, continuity, and density-strength relationship.

Answer the following questions:

Question 1. Why does freely suspended magnet always settle in the north-south direction?
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र पृथ्वी को एक विशाल चुंबक के रूप में दर्शाता है, जिसके अंदर एक बड़ा बार चुंबक होने की कल्पना की गई है। पृथ्वी की चुंबकीय बल रेखाएँ भौगोलिक उत्तरी ध्रुव के पास से निकलती हैं और भौगोलिक दक्षिणी ध्रुव में प्रवेश करती हैं। यह स्पष्ट करता है कि एक स्वतंत्र रूप से निलंबित चुंबक क्यों हमेशा उत्तर-दक्षिण दिशा में संरेखित होता है, क्योंकि यह पृथ्वी के चुंबकीय क्षेत्र के साथ खुद को पंक्तिबद्ध करता है।
Answer: 1. Gilbert gave a scientific explanation that earth itself is a gigantic magnet. 2. The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth since unlike poles attract. 3. It means that the south pole of some gigantic magnet must be near the geographic north pole of the earth. 4. In other words, the thing we call Earth's geographic north pole is actually the south pole of the magnet inside the earth. 5. That is why a freely suspended magnet always settles in geographic north-south attracted by opposite poles of the earth as a great magnet.
In simple words: A freely suspended magnet aligns North-South because Earth itself acts like a giant magnet, and its magnetic field attracts the opposite poles of the suspended magnet, causing it to orient along the Earth's magnetic axis.

🎯 Exam Tip: The key reason is the interaction between the suspended magnet's poles and the Earth's internal magnetic field, where the geographic north attracts the magnet's north pole (which is actually a magnetic south pole). Keep the geographical vs magnetic poles clear.

Question 2. Which magnetic poles attract each other?
Answer: Opposite magnet poles attract each other.
In simple words: Magnetic poles that are different, like a north pole and a south pole, will pull towards each other.

🎯 Exam Tip: Always remember the fundamental rule: unlike poles attract.

Question 3. Which pole of a spherical magnet will get attracted towards the south pole of the bar magnet?
Answer: The north pole of the spherical magnet will get attracted towards the south pole of the bar magnet.
In simple words: According to the rule of magnetism, the north pole of a spherical magnet will be drawn towards the south pole of a bar magnet.

🎯 Exam Tip: This question tests your understanding of the basic law of magnetic attraction: opposite poles attract.

Question 4. Why does a bar magnet kept at a distance doesn't attract pins?
Answer:
1. The region around the magnet where the magnetic force acts is known as the magnetic field.
2. It has its influence over a certain distance where these magnetic lines of force act.
3. As these pins are outside this area of influence, a bar magnet does not attract those pins which are at a distance.
In simple words: A magnet has a magnetic field around it, but its force decreases with distance. Pins placed outside this field's effective range will not be attracted by the magnet.

🎯 Exam Tip: Focus on explaining the concept of a magnetic field and its range of influence when answering questions about magnetic attraction.

Question 5. What is an electromagnet?
Answer:
1. A soft metal core made into a magnet by the passage of electric current through a coil surrounding it is called an electromagnet.
2. An electromagnet is a magnet in which the magnetic field is produced by electricity.
3. The strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it.
4. The poles of an electromagnet can even be reversed by reversing the flow of electricity.
5. An electromagnet works because an electric current produces a magnetic field.
6. The magnetic field produced by electric current forms circles around the electric current.
7. The magnetic field disappears when the current is turned off.
In simple words: An electromagnet is a temporary magnet created when an electric current flows through a wire coiled around a soft iron core. Its strength and polarity can be controlled by adjusting the current.

🎯 Exam Tip: Remember that electromagnets are temporary and their properties can be controlled, unlike permanent magnets.

Question 6. How can an electromagnet be made?
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक साधारण इलेक्ट्रोमैग्नेट (विद्युत चुंबक) बनाने का तरीका दिखाता है। इसमें एक लोहे की कील (iron nail) पर तांबे का तार (copper wire) लपेटा गया है, और इस तार को एक बैटरी (battery) से जोड़ा गया है। बैटरी से प्रवाहित विद्युत धारा लोहे की कील को एक अस्थायी चुंबक में बदल देती है, जिससे वह छोटी पिनों (pins) को आकर्षित कर सकती है।
1. It is easy to make an electromagnet. To make an electromagnet we needs an iron nail of 10 cm length 1 metre long insulated copper wire, a battery cell, pins.
2. Neatly wrap some insulated copper wire around an iron nail.
3. The more wires you wrap around the nail, the stronger will be the electromagnet.
4. Attach a battery to the wire, an electric current will begin to flow and the iron nail will become magnetised.
5. When the battery is disconnected the iron nail will lose its magnetism.
In simple words: To make an electromagnet, wrap insulated copper wire around an iron nail and connect the wire ends to a battery. The current flowing through the coil will magnetize the nail, and disconnecting the battery will remove the magnetism.

🎯 Exam Tip: Detail the components and steps involved in creating an electromagnet, emphasizing the temporary nature of the magnetism induced by electric current.

Use Your Brainpower!

Question 1. Which direction will a magnetic needle show on the geographic north pole?
Answer:
North, all magnetic needle will show north direction.
In simple words: At the geographic North Pole, a magnetic needle would point towards the geographic North, aligning with the Earth's magnetic field which has an effective magnetic south pole near the geographic north.

🎯 Exam Tip: Understand the difference between geographic poles and magnetic poles to correctly answer questions about compass behavior.

Question 2. Is magnetic force a vector or a scalar quantity?
Answer:
1. It is a vector quantity. Because a magnetic field is the magnetic effect of electric current and magnetic materials.
2. The magnetic field at any given point is specified by both direction and magnitude as such it is represented by a vector field.
In simple words: Magnetic force is a vector quantity because it has both magnitude (strength) and direction. This is evident as magnetic fields, which cause magnetic force, are themselves vector fields.

🎯 Exam Tip: Remember that any physical quantity possessing both magnitude and direction is a vector quantity.

Question 3. What is meant by magnetic force?
Answer:
1. The magnetic force, is a consequence of the electromagnet force, one of the four fundamental forces of nature.
2. It occurs whenever objects interact in which there is charge in motion, eg. compass, a motor.
3. Magnetic force is an attraction or repulsion that arises between electrically charged particles because of their motion.
In simple words: Magnetic force is the attractive or repulsive force between charged particles due to their motion, mediated by magnetic fields. It is a fundamental force of nature.

🎯 Exam Tip: Define magnetic force by its nature (attraction/repulsion) and its origin (moving charged particles or magnets).

Question 4. How does a magnetic force act without direct contact?
Answer:
Magnetic force acts without even direct contact because of the penetrating ability of the magnetic field.
In simple words: Magnetic force acts without direct contact because magnets create an invisible magnetic field around them. This field extends through space and exerts force on other magnetic materials or moving charges within its range.

🎯 Exam Tip: The concept of a "field" (like a magnetic field) explains how forces can act over a distance without physical contact.

Question 5. What is the difference between the gravitational force and magnetic force?
Answer:

In simple words: Gravitational force attracts all objects with mass over long distances, while magnetic force acts on specific materials (like iron) and can either attract or repel, usually over shorter distances.

🎯 Exam Tip: Clearly differentiate between the source, range, and nature (always attractive vs. attractive/repulsive) of gravitational and magnetic forces.

Question 6. Why is repulsion the real test for identifying a magnet?
Answer:
A magnet can attract the opposite pole of the magnet as well as magnetic substances (iron, cobalt, nickel).
So if a magnet attracts another object, we cannot say that other object is a magnet or a magnetic substance.
But if the magnet repels the object then we can surely say that the other object is a magnet because like poles of magnets repel each other.
In simple words: Repulsion is the true test for a magnet because while a magnet attracts both opposite poles and magnetic substances, only like poles of two magnets will repel each other. Attraction alone doesn't distinguish between a magnet and a magnetic material.

🎯 Exam Tip: Emphasize that attraction can occur between a magnet and a magnetic material, but repulsion can only occur between two magnets (like poles).

Question 7. How will you find a magnet from among the various articles given to you?
Answer:
1. Magnet has the property to attract things made of iron, cobalt, nickel.
2. A magnet has magnetic field which is invisible but it has the property of attracting, pulling other
3. ferromagnetic material such as iron, cobalt and nickle.
4. So if we bring any iron, nickle objects near it, they will be pulled toward the magnet.
5. The real test is repulsion.
6. The article which shows repulsion when one of the poles of a magnet is brought near is surely a magnet.
In simple words: To identify a magnet, first check if it attracts magnetic materials like iron. Then, use a known magnet to test for repulsion; if it repels, the article is definitely a magnet, as only like poles of magnets repel each other.

🎯 Exam Tip: Provide a two-step process: initial attraction test followed by the definitive repulsion test using a known magnet.

Answer the following questions:

Question 1. Why does the magnetic needle of a compass not settle parallel to the ground but at an angle to it?
Answer:
1. Freely suspended magnet does not point to north, but aligns to earth's magnetic field axially ie – north-south.
2. The magnetic pole of the earth is different from true north (geographic north) because the magnetic north is constantly changing.
3. It leads to a margin of error called declination in which there is an angle of difference (11.51)° between Magnetic North and True North.
4. That is the reason the magnetic needle does not settle parallel to the ground.
In simple words: A compass needle doesn't settle parallel to the ground because Earth's magnetic field lines are not parallel to the surface everywhere; they dip into the Earth. This "magnetic dip" causes the needle to align at an angle.

🎯 Exam Tip: Understand the concept of "magnetic dip" or "inclination" which causes a compass needle to tilt vertically, rather than just horizontally.

Observe the diagrams and answer the questions given below:

ℹ️ चित्र व्याख्या (Diagram Explanation): ये चित्र एक स्टील बार को चुंबकित करने की दो अलग-अलग विधियों को दर्शाते हैं। ऊपर वाला चित्र 'एकल स्पर्श विधि' दिखाता है जहाँ एक चुंबक को स्टील बार पर एक ही दिशा में कई बार रगड़ा जाता है। नीचे वाला चित्र 'दोहरा स्पर्श विधि' दिखाता है जहाँ दो चुंबकों को स्टील बार के मध्य से विपरीत दिशाओं में रगड़ा जाता है, जिससे अधिक मजबूत चुंबकत्व उत्पन्न होता है।

Question 1. Name the methods shown.
Answer:
Single touch and Double touch methods of magnetising a steel bar.
In simple words: The two methods shown for magnetizing a steel bar are the single touch method and the double touch method.

🎯 Exam Tip: Be able to identify common magnetization methods from their visual representations or descriptions.

Question 2. Give 2 points of difference between the methods.
Answer:

In simple words: In the single touch method, one magnet is stroked along the steel bar in one direction, producing weaker, temporary magnetism. In the double touch method, two magnets are stroked from the center outwards in opposite directions, resulting in stronger, longer-lasting magnetism.

🎯 Exam Tip: When comparing methods, highlight the number of magnets used, the stroking technique, and the resulting strength and duration of magnetism.