5. Magnetism and Matter
рдЗрд╕ рдкреЗрдЬ рдкрд░ рдЖрдкрдХреЛ 5. Magnetism and Matter рдХреЗ рд╕рднреА рдорд╣рддреНрд╡рдкреВрд░реНрдг рдмрд╣реБрд╡рд┐рдХрд▓реНрдкреАрдп рдкреНрд░рд╢реНрди (MCQ), рдкрд░реАрдХреНрд╖рд╛ рдЙрдкрдпреЛрдЧреА рдиреЛрдЯреНрд╕ рдФрд░ рдСрдирд▓рд╛рдЗрди рдХреНрд╡рд┐рдЬрд╝ рдорд┐рд▓реЗрдВрдЧреЗред рдЕрдкрдиреЗ рдЬреНрдЮрд╛рди рдХрд╛ рдкрд░реАрдХреНрд╖рдг рдХрд░рдиреЗ рдФрд░ рдмреЛрд░реНрдб/рдкреНрд░рддрд┐рдпреЛрдЧреА рдкрд░реАрдХреНрд╖рд╛ рдореЗрдВ рд╢рдд-рдкреНрд░рддрд┐рд╢рдд рдЕрдВрдХ рдкреНрд░рд╛рдкреНрдд рдХрд░рдиреЗ рдХреЗ рд▓рд┐рдП рдиреАрдЪреЗ рджрд┐рдП рдЧрдП рдореЙрдХ рдЯреЗрд╕реНрдЯ рдореЗрдВ рдЕрд╡рд╢реНрдп рднрд╛рдЧ рд▓реЗрдВред
ЁЯСЙ рдЕрдзреНрдпрд╛рдп рдХрд╛ рд╕рд╛рд░рд╛рдВрд╢ (Summary)
Dear students, in this chapter, we will study 1 extremely fascinating, ancient, and highly practical branch of physics that explores the hidden magnetic properties of various materials around us: 'Magnetism and Matter'. In the previous chapter, we deeply studied how 1 moving electric charge naturally produces 1 magnetic field. But what about permanent magnets? You must have played with 1 small black magnet in your childhood, sticking it to 1 iron almirah or 1 refrigerator door. Have you ever thought deeply about where this magical pulling force exactly comes from, even when there is absolutely 0 electric current flowing through it? The 100 percent scientific truth is that inside every single atom of 1 magnetic material, the tiny electrons revolving around the nucleus act exactly like microscopic current loops. These microscopic loops generate their own tiny magnetic dipole moments. When billions of these atomic magnets beautifully align themselves in 1 specific direction, the entire material magically becomes 1 strong permanent magnet.
Instead of just cramming complex science in closed books, if we logically connect physics with our beautiful planet Earth, it feels extremely wonderful. Do you know that our giant Earth itself acts exactly like 1 massive bar magnet? The geographical North Pole and South Pole of our Earth have magnetic poles associated with them. This is the exact 100 percent scientific reason why 1 freely suspended magnetic compass needle always aligns itself in the North-South direction. This simple but highly powerful device has successfully guided sailors and travelers across massive oceans for 1000s of years. Furthermore, in today's modern world, the massive data stored inside your computer's hard drive or the magnetic strip on the back of 1 ATM card strictly relies on the fundamental principles of magnetism to safely store information.
From the strict perspective of the upcoming NCERT and RBSE board exams, this specific chapter of physics is highly scoring and extremely important for your 100 percent success. In the board exams, not only direct theoretical questions are asked from this chapter, but excellent analytical and conceptual questions on Earth's magnetism, magnetic properties of materials, and hysteresis loop definitely appear in the final exam paper every single year without fail. In this highly exciting journey, we will 1st study the basic properties of 1 bar magnet very closely. We will scientifically learn about magnetic field lines, which form 100 percent continuous closed loops, unlike electric field lines. We will also logically calculate the magnetic field produced by 1 magnetic dipole at various points.
Moving 1 little further in the chapter, we will deeply study the highly important elements of Earth's magnetic field: magnetic declination, magnetic dip or inclination, and the horizontal component. Understanding these 3 parameters is 100 percent necessary to exactly locate the magnetic field at any specific place on Earth. After this, we will logically analyze the fascinating magnetic properties of various materials and broadly classify them into 3 main categories: diamagnetic, paramagnetic, and ferromagnetic substances. We will clearly see how ferromagnetic materials like iron, cobalt, and nickel are strongly attracted by magnets and are strictly used to make permanent magnets and electromagnets. Finally, we will understand the concept of magnetic susceptibility, permeability, and the crucial Hysteresis curve, which helps us select the exact perfect material for making 1 transformer core.
To perfectly ensure your excellent and 100 percent strong preparation, we have meticulously selected and prepared completely accurate, high-level, and highly exam-useful objective questions (MCQs) from all these complex topics. By continuously practicing again and again, you will surely learn critical time management and massively increase your speed of solving complex questions without making even 1 single mistake.
Feature: This is 1 3-Level based unique quiz. To unlock the next level (Level 2 and 3), students must score at least 70% in the current level, making their board exam preparation 100% strong.
рдорд╣рддреНрд╡рдкреВрд░реНрдг рдкреНрд░рд╢реНрди (Important Questions)
PDF рдбрд╛рдЙрдирд▓реЛрдб рдХрд░реЗрдВрдЕрдзреНрдпрд╛рдп рдХреЗ рд╕рднреА рдкреНрд░рд╢реНрди (Revision Notes)
*рдиреЛрдЯ: рдпрд╣ рд╕реЗрдХреНрд╢рди рд░рд┐рд╡реАрдЬрди рдХреЗ рд▓рд┐рдП рд╣реИред рдЕрдкрдирд╛ рдЬреНрдЮрд╛рди рдкрд░рдЦрдиреЗ рдХреЗ рд▓рд┐рдП рдКрдкрд░ рджрд┐рдП рдЧрдП рдХреНрд╡рд┐рдЬрд╝ рдореЗрдВ рднрд╛рдЧ рд▓реЗрдВред
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Distance between two poles of a bar magnet is called?
A) Effective length | B) Geometric length | C) Diameter | D) Radius -
Magnetic field lines form?
A) Closed curves | B) Open curves | C) Straight lines | D) None -
Gauss's law for magnetism is?
A) тИоB.dS = 0 | B) тИоE.dS = Q/╬╡тВА | C) V = IR | D) None -
Vertical component of Earth's field is zero at?
A) Poles | B) Magnetic equator | C) 45┬░ latitude | D) Everywhere -
Angle of Dip at poles is?
A) 0┬░ | B) 45┬░ | C) 90┬░ | D) 180┬░ -
Unit of magnetic susceptibility (Chi) is?
A) A/m | B) T | C) Unitless | D) Wb -
Substance like iron which is strongly attracted is called?
A) Diamagnetic | B) Paramagnetic | C) Ferromagnetic | D) None -
At Curie temperature, ferromagnetic substance becomes?
A) Diamagnetic | B) Paramagnetic | C) Permanent magnet | D) None -
Best material for making permanent magnets?
A) Soft iron | B) Steel | C) Copper | D) Aluminum -
Best material for making electromagnets?
A) Soft iron | B) Steel | C) Cobalt | D) Nickel -
Unit of magnetic intensity (H) is?
A) Ampere/meter | B) Tesla | C) Weber | D) Gauss -
Position of magnetic needle at Earth's magnetic pole will be?
A) Horizontal | B) Vertical | C) Inclined at 45┬░ | D) Uncertain -
Susceptibility of diamagnetic substances is?
A) Positive and low | B) Negative and low | C) Positive and high | D) Zero -
Angle between magnetic meridian and geographic meridian is?
A) Angle of dip | B) Magnetic declination | C) Critical angle | D) None -
Direction of magnetic moment is?
A) N to S | B) S to N | C) East to West | D) None -
Susceptibility of paramagnetic substances varies with temp (T) as?
A) Increases | B) Proportional to 1/T (Curie Law) | C) Independent | D) Decreases -
Magnetic lines don't intersect because?
A) Parallel | B) Direction won't be unique | C) Scalar | D) None -
Retentivity of soft iron compared to steel is?
A) More | B) Less | C) Same | D) Zero -
Coercivity of steel compared to soft iron is?
A) More | B) Less | C) Equal | D) Zero -
Diamagnetic substances move in magnetic field from?
A) Low to high field | B) High to low field | C) Perpendicular | D) Nowhere -
Direction of lines inside a magnet is?
A) N to S | B) S to N | C) Outwards | D) Zero -
Relation between permeability (┬╡r) and susceptibility (╧З)?
A) ┬╡r = 1 + ╧З | B) ┬╡r = ╧З - 1 | C) ┬╡r = 1/╧З | D) None -
Earth behaves as magnet with north pole near geographic .........?
A) North | B) South | C) East | D) West -
Area of Hysteresis Loop represents?
A) Magnetic force | B) Energy loss per cycle | C) Magnetic potential | D) None -
Superconductors are perfect .........?
A) Diamagnetic | B) Paramagnetic | C) Ferromagnetic | D) Conductors -
Field in axial position varies with distance (r) as?
A) 1/r^2 | B) 1/r^3 | C) 1/r | D) r^2 -
Unit of magnetic potential (V) can be?
A) Joule/Ampere-meter | B) Weber | C) Tesla | D) Volt -
Magnetism of magnet on heating?
A) Increases | B) Decreases | C) Remains stable | D) Becomes zero -
Susceptibility of vacuum is?
A) 1 | B) Zero | C) -1 | D) Infinity -
Density of field lines represents?
A) Strong field | B) Weak field | C) Zero field | D) Direction -
Dip angle is 0┬░ at equator, vertical component (Bv) will be?
A) Equal to B | B) Zero | C) B/2 | D) Infinity -
If dip angle is 45┬░, then Bh and Bv are?
A) Bh > Bv | B) Bh < Bv | C) Bh = Bv | D) Bv = 0 -
Work to rotate 1.2 A-m^2 moment by 90┬░ in 0.5 T field?
A) 0.6 J | B) 1.2 J | C) 0.5 J | D) Zero -
Value of ┬╡r for ferromagnetic material is?
A) < 1 | B) = 1 | C) >> 1 | D) 0 -
Relation between effective length (L) and geometric length (Lg)?
A) L = 0.84 Lg | B) L = Lg | C) L = 2 Lg | D) L = 0.5 Lg -
Bh = 0.3 G and Bv = 0.4 G at a place, total field (B) is?
A) 0.7 G | B) 0.1 G | C) 0.5 G | D) Zero -
Needle position on taking it to poles?
A) Horizontal | B) Vertical | C) Rotates | D) Stable -
Iron above Curie temp (1043 K) behaves as?
A) Paramagnetic | B) Diamagnetic | C) Ferromagnetic | D) Non-magnetic -
Transformer core made of soft iron to reduce?
A) Steel loss | B) Hysteresis loss | C) Copper loss | D) Aluminum loss -
Meissner effect is related to?
A) Diamagnetism | B) Paramagnetism | C) Conductivity | D) None -
Pole strength on cutting magnet into two equal parts (perpendicular)?
A) Halved | B) Remains same | C) Doubled | D) Zero -
Pole strength on cutting magnet parallel to length?
A) Halved | B) Remains same | C) Doubled | D) Zero -
Permeability (┬╡) if B=1.5 T on applying H=1000 A/m?
A) 1.5 x 10^-3 | B) 1.5 | C) 1500 | D) 0 -
B at equator compared to axial position?
A) Half | B) Double | C) Same | D) Zero -
Moment due to orbital motion of electron in atom is?
A) Bohr Magneton | B) Nuclear moment | C) Spin moment | D) None
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