Tiêu đề 05. MAGNETISM AND MATTER.pdf ✅

BUY COURSE FROM STORE TO GET INSTANT ANSWER AND EXPLANATION OF EACH QUESTION SPARK PCMB | DOWNLOAD APP NOW| +91-920-630-6398 05. MAGNETISM AND MATTER #QID# 31073 (1.) The χ − 1/T graph for an alloy of paramagnetic nature is shown in fig. the curie constant is (a.) 57 K (b.) 2.8 × 10−3K (c.) 570 K (d.) 17.5 × 10−3K Ans: a Exp: (a) X = C × 1 T = 0.4 7 × 10−3 = 57K #QID# 31074 (2.) If a diamagnetic substance is brought near north or south pole of a bar magnet, it is (a.) Attracted by the poles (b.) Repelled by the poles (c.) Repelled by the north pole and attracted by the south pole (d.) Attracted by the north pole and repelled by the south pole Ans: b Exp: (b) Repelled due to induction of similar poles #QID# 31075 (3.) If a bar magnet of length l and cross-sectional area A is cut into two equal parts as shown in figure, then the pole strength of each pole becomes
BUY COURSE FROM STORE TO GET INSTANT ANSWER AND EXPLANATION OF EACH QUESTION SPARK PCMB | DOWNLOAD APP NOW| +91-920-630-6398 (a.) Half (b.) Double (c.) One-fourth (d.) Four time Ans: a Exp: (a) Pole strength depends on material of magnet, state of magnetization and cross- sectional area. As m ∝ A, so if A becomes half, pole strength gets half. #QID# 31076 (4.) A bar magnet A of magnetic moment MA is found to oscillate at a frequency twice that of magnet B of magnetic moment MB when placed in a vibrating magneto − meter. We may say that (a.) MA = 2MB (b.) MA = 8MB (c.) MA = 4MB (d.) MB = 8MA Ans: c Exp: (c) c = 1 2π √ MBH I ⇒ v ∝ √M ⇒ vA vB = √ MA MB ⇒ 2 1 = √ MA MB ⇒ MA = 4 MB #QID# 31077
BUY COURSE FROM STORE TO GET INSTANT ANSWER AND EXPLANATION OF EACH QUESTION SPARK PCMB | DOWNLOAD APP NOW| +91-920-630-6398 (5.) The magnetic lines of force inside a bar magnet (a.) Are from north-pole to south-pole of the magnet (b.) Do not exist (c.) Depend upon the area of cross-section of the bar magnet (d.) Are from south-pole to north-pole of the magnet Ans: d Exp: (d) Inside bar magnet, lines of force are from south to north. #QID# 31078 (6.) The magnet can be completely demagnetized by (a.) Breaking the magnet into small pieces (b.) Heating it slightly (c.) Droping it into ice cold water (d.) A reverse field of appropriate strength Ans: d #QID# 31079 (7.) A small bar magnet of moment M is placed in a uniform field H. If magnet makes an angle of 30° with field, the torque acting on the magnet is (a.) MH (b.) MH 2 (c.) MH 3 (d.) MH 4 Ans: b Exp: (b) τ = MH sin θ = MH sin 30° = MH 2 #QID# 31080 (8.) A current carrying small loop behaves like a small magnet. If A be its area and M its magnetic moment, the current in the loop will be
BUY COURSE FROM STORE TO GET INSTANT ANSWER AND EXPLANATION OF EACH QUESTION SPARK PCMB | DOWNLOAD APP NOW| +91-920-630-6398 (a.) M/A (b.) A/M (c.) MA (d.) AM2 Ans: a Exp: (a) Magnetic moment, M = iA ⇒ i = M A #QID# 31081 (9.) Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show (a.) Paramagnetism (b.) Anti-ferromagnetism (c.) No magnetic property (d.) Diamagnetism Ans: a Exp: (a) If the temperature of a ferromagnetic material is raised above a certain critical value, called the Curie temperature, the exchange coupling ceases to be effective. Most such materials then become simply paramagnetic; that is, the dipoles still tend to align with an external field but much more weakly, and thermal agitation can now more easily disrupt the alignment. #QID# 31082 (10.) Force between two identical short bar magnets whose centers are r metre apart is 8.1 N, when their axes are along the same line. If separation is increased to 3 r and the axis are rearranged perpendicularly, the force between them would become (a.) 2.4 N (b.) 1.2 N (c.) 0.1 N (d.) 1.15 N Ans: c