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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 2151. |
A homogeneous solid cylinder of length L (\[L |
| A. | \[\frac{5}{4}d\] |
| B. | \[\frac{d}{4}\] |
| C. | \[4d\] |
| D. | \[\frac{d}{5}\] |
| Answer» B. \[\frac{d}{4}\] | |
| 2152. |
Two non-mixing liquids of densities \[\rho \] and n\[\rho \] \[(n>1)\] are put in a container. The height of each liquid is h. A solid cylinder of length L and density d is put in this container. The cylinder floats with its axis vertical and length \[pL(p |
| A. | \[\left\{ l+\left( n+l \right)p \right\}\rho ~~\] |
| B. | \[~\left\{ 2+\left( n+1 \right)p \right\}\rho \] |
| C. | \[\left\{ 2+\left( n-1 \right)p \right\}\rho \] |
| D. | \[\left\{ l+\left( n-1 \right)p \right\}\rho \] |
| Answer» E. | |
| 2153. |
The density p of water of bulk modulus B at a depth y in the ocean is related to the density at surface\[{{\rho }_{0}}\] by the relation |
| A. | \[\rho ={{\rho }_{0}}\left[ 1-\frac{{{\rho }_{0}}gy}{B} \right]\] |
| B. | \[\rho ={{\rho }_{0}}\left[ 1+\frac{{{\rho }_{0}}gy}{B} \right]\] |
| C. | \[\rho ={{\rho }_{0}}\left[ 1+\frac{B}{{{\rho }_{0}}hgy} \right]\] |
| D. | \[\rho ={{\rho }_{0}}\left[ 1-\frac{B}{{{\rho }_{0}}hgy} \right]\] |
| Answer» C. \[\rho ={{\rho }_{0}}\left[ 1+\frac{B}{{{\rho }_{0}}hgy} \right]\] | |
| 2154. |
A wooden block, with a coin placed on its top, floats in water as shown in fig. the distance 1 and h are shown there. After some time the coin falls into the water. Then |
| A. | \[\ell \]decreases and h increases |
| B. | \[\ell \]increases and h decreases |
| C. | Both \[\ell \]and h increases |
| D. | Both \[\ell \] and h decreases |
| Answer» E. | |
| 2155. |
A uniform rod of density p is placed in a wide tank containing a liquid of density\[{{\rho }_{0}}({{\rho }_{0}}>\rho )\].The depth of liquid in the tank is half the length of the rod. The rod is in equilibrium, with its lower end resting on the bottom of the tank. In this position the rod makes an angle 9 with the horizontal, then: |
| A. | \[\sin \theta =\frac{1}{2}\sqrt{{{\rho }_{0}}/\rho }\] |
| B. | \[\sin \theta =\frac{1}{2},\frac{{{\rho }_{0}}}{\rho }\] |
| C. | \[\sin \theta =\sqrt{\rho /{{\rho }_{0}}}\] |
| D. | \[\sin \theta ={{\rho }_{0}}/\rho \] |
| Answer» B. \[\sin \theta =\frac{1}{2},\frac{{{\rho }_{0}}}{\rho }\] | |
| 2156. |
A solid sphere of density \[\eta (>1)\] times lighter than water is suspended in a water tank by a string tied to its base as shown in fig. If the mass of the Sphere is/w, then the tension in the string is given by |
| A. | \[\left( \frac{\eta -1}{\eta } \right)mg\] |
| B. | \[\eta mg\] |
| C. | \[\frac{mg}{\eta -1}\] |
| D. | \[(\eta -1)mg\] |
| Answer» E. | |
| 2157. |
A hemispherical bowl just floats without sinking in a liquid of density\[1.2\times {{10}^{3}}kg/{{m}^{3}}\]. If outer diameter and the density of the bowl are 1 m and \[2\times {{10}^{4}}kg/{{m}^{3}}\]respectively then the inner diameter of the bowl will be |
| A. | 0.94 m |
| B. | 0.97 m |
| C. | 0.98 m |
| D. | 0.99 m |
| Answer» D. 0.99 m | |
| 2158. |
What is the absolute pressure of the gas above the liquid surface in the tank shown in fig. Density of \[oil=820kg/{{m}^{3}}\], density of mercury\[=13.6\times {{10}^{3}}kg/{{m}^{3}}\] Given 1 atmospheric pressure\[=1.01\times {{10}^{5}}N/{{m}^{2}}\] |
| A. | \[3.81\times {{10}^{5}}N/{{m}^{2}}\] |
| B. | \[6\times {{10}^{6}}N/{{m}^{2}}\] |
| C. | \[5\times {{10}^{7}}N/{{m}^{2}}\] |
| D. | \[4.6\times {{10}^{2}}N/{{m}^{2}}\] |
| Answer» B. \[6\times {{10}^{6}}N/{{m}^{2}}\] | |
| 2159. |
Figure shows a U-tube of uniform cross-sectional area A, accelerated with acceleration a as shown. If d is the separation between the limbs, then what is the difference in the levels of the liquid in the U-tube is |
| A. | \[\frac{ad}{g}\] |
| B. | \[\frac{ag}{d}\] |
| C. | \[\frac{a}{d}\] |
| D. | \[\frac{dg}{a}\] |
| Answer» B. \[\frac{ag}{d}\] | |
| 2160. |
A cone fall of water, is placed on its side on a horizontal table, the thrust on its base is x times the weight of the contained fluid, where 2a is the vertical angle of the cone. Find the value of x. |
| A. | \[3\cos \,\alpha \] |
| B. | \[3\sin \,\alpha \] |
| C. | \[2\sin \,\alpha \] |
| D. | \[2\cos \,\alpha \] |
| Answer» C. \[2\sin \,\alpha \] | |
| 2161. |
An iceberg is floating in ocean. What fraction of its volume is above the water? (Given: density of ice\[=900kg/{{m}^{3}}\] and density of ocean water \[=1030kg/{{m}^{3}}\]) |
| A. | \[\frac{90}{103}\] |
| B. | \[\frac{13}{103}\] |
| C. | \[\frac{10}{103}\] |
| D. | \[\frac{1}{103}\] |
| Answer» C. \[\frac{10}{103}\] | |
| 2162. |
A sphere of solid material of specific gravity 8 has a concentric spherical cavity and just sinks in water. The ratio of radius of cavity to that of outer radius of the sphere must be |
| A. | \[\frac{{{7}^{1/3}}}{2}\] |
| B. | \[\frac{{{5}^{1/3}}}{2}\] |
| C. | \[\frac{{{9}^{1/3}}}{2}\] |
| D. | \[\frac{{{3}^{1/3}}}{2}\] |
| Answer» B. \[\frac{{{5}^{1/3}}}{2}\] | |
| 2163. |
A right circular cone of density p, floats just immersed with its vertex downwards in a vessel containing two liquids of densities \[{{\rho }_{1}}\]and \[{{\rho }_{2}}\] respectively, the planes of separation of the two liquids cuts off from the axis of the cone a fraction z of its length. Find z. |
| A. | \[{{\left( \frac{\rho +{{\sigma }_{2}}}{{{\sigma }_{1}}+{{\sigma }_{2}}} \right)}^{1/3}}\] |
| B. | \[{{\left( \frac{\rho -{{\sigma }_{2}}}{{{\sigma }_{1}}-{{\sigma }_{2}}} \right)}^{1/3}}\] |
| C. | \[{{\left( \frac{\rho -{{\sigma }_{2}}}{{{\sigma }_{1}}+{{\sigma }_{2}}} \right)}^{1/2}}\] |
| D. | \[{{\left( \frac{\rho -{{\sigma }_{2}}}{{{\sigma }_{1}}-{{\sigma }_{2}}} \right)}^{1/2}}\] |
| Answer» C. \[{{\left( \frac{\rho -{{\sigma }_{2}}}{{{\sigma }_{1}}+{{\sigma }_{2}}} \right)}^{1/2}}\] | |
| 2164. |
A thin tube sealed at both ends is 100 cm long. It lies horizontally, the middle 20 cm containing mercury and two equal ends containing air at standard atmospheric pressure. If the tube is now fumed to a vertical position, by what amount will the mercury be displaced? (Given: cross-section of the tube can be assumed to be uniform) |
| A. | 2.95cm |
| B. | 5.18cm |
| C. | 8.65cm |
| D. | 0.0cm |
| Answer» C. 8.65cm | |
| 2165. |
A hemispherical portion of radius R is removed from the bottom of a cylinder of radius R. The volume of the remaining cylinder is T and its mass M. It is suspended by a string in a liquid of density p where it stays vertical. The upper surface of the cylinder is at a depth h below the liquid surface. The force on the bottom of the cylinder by the liquid is |
| A. | \[Mg\] |
| B. | \[Mg-V\rho g\] |
| C. | \[Mg+\pi {{R}^{2}}h\rho g\] |
| D. | \[\rho g(V+\pi {{R}^{2}}h)\] |
| Answer» E. | |
| 2166. |
In rising from the bottom of a lake, to the top, the temperature of an air bubble remains unchanged, but its diameter gets doubled. If h is the barometric height (expressed in m of mercury of relative density p) at the surface of the lake, the depth of the lake is |
| A. | \[8\text{ }\rho hm\] |
| B. | \[\text{7 }\rho hm\] |
| C. | \[\text{9 }\rho hm\] |
| D. | \[\text{12 }\rho hm\] |
| Answer» C. \[\text{9 }\rho hm\] | |
| 2167. |
The total weight of a piece of wood is 6 kg. In the floating state in water its \[\frac{1}{3}\] part remains inside the water. On this floating piece of wood what maximum weight is to be put such that the whole of the piece of wood is to be drowned in the water? |
| A. | 15 kg |
| B. | 14 kg |
| C. | 10 kg |
| D. | 12 kg |
| Answer» E. | |
| 2168. |
A bar magnet of magnetic moment \[3.0\,A-{{m}^{2}}\] is placed in a uniform magnetic field of \[2\times {{10}^{-5}}T\].If each pole of the magnet experiences a force of \[6\times {{10}^{-4}}N\], the length of the magnet is |
| A. | 0.5 m |
| B. | 0.3 m |
| C. | 0.2 m |
| D. | 0.1 m |
| Answer» E. | |
| 2169. |
The coercivity of a small magnet where the ferromagnet gets demagnetized is\[3\times {{10}^{3}}\,A{{m}^{-1}}\]. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is: |
| A. | 30 mA |
| B. | 60 mA |
| C. | 3 A |
| D. | 0.25 |
| Answer» D. 0.25 | |
| 2170. |
The mass of a speciment of a ferromagnetic material is 0.6 kg. and its density is \[7.8\times {{10}^{3}}\,kg/{{m}^{3}}\]. If the area of hysteresis loop of alternating magnetising field of frequency 50Hz is 0.722 MKS units then the hysteresis loss per second will be |
| A. | \[277.7\times {{10}^{-5}}\,joule\] |
| B. | \[277.7\times {{10}^{-6}}\,joule\] |
| C. | \[277.7\times {{10}^{-4}}\,joule\] |
| D. | \[27.77\times {{10}^{-4}}\,joule\] |
| Answer» B. \[277.7\times {{10}^{-6}}\,joule\] | |
| 2171. |
A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of l .2 amp? |
| A. | 4.48 T |
| B. | 2.48 T |
| C. | 5.48 T |
| D. | 3.12T |
| Answer» B. 2.48 T | |
| 2172. |
An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is put in a magnetic field of intensity B, the magnetic field \[{{B}_{s}}\] inside the superconductor will be such that: |
| A. | \[{{B}_{s}}=-B\] |
| B. | \[{{B}_{s}}=0\] |
| C. | \[{{B}_{s}}=B\] |
| D. | \[{{B}_{s}}<B\] but \[Bs\ne 0\] |
| Answer» C. \[{{B}_{s}}=B\] | |
| 2173. |
A domain in a ferromagnetic substance is in the form of a cube of side length\[1\mu m\]. If it contains \[8\times {{10}^{10}}\] atoms and each atomic dipole has a dipole moment of \[9\times {{10}^{-24}}\,A\,,{{m}^{2}}\], then the magnetization of the domain is |
| A. | \[7.2\times {{10}^{5}}\,A\,{{m}^{-1}}\] |
| B. | \[7.2\times {{10}^{3}}\,A\,{{m}^{-1}}\] |
| C. | \[7.2\times {{10}^{9}}\,A\,{{m}^{-1}}\] |
| D. | \[7.2\times {{10}^{12}}\,A\,{{m}^{-1}}\] |
| Answer» B. \[7.2\times {{10}^{3}}\,A\,{{m}^{-1}}\] | |
| 2174. |
A permanent magnet in the shape of a thin cylinder of length 10 cm has magnetisation (M) \[={{10}^{6}}\,A\,{{m}^{-1}}\]. Its magnetization current\[{{I}_{M}}\]is |
| A. | \[{{10}^{5}}\,A\] |
| B. | \[{{10}^{6}}\,A\] |
| C. | \[{{10}^{7}}\,A\] |
| D. | \[{{10}^{8}}\,A\] |
| Answer» B. \[{{10}^{6}}\,A\] | |
| 2175. |
If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by\[{{\mu }_{d}}\],\[{{\mu }_{p}}\]and\[{{\mu }_{f}}\]respectively, then |
| A. | \[{{\mu }_{d}}=0\] and \[{{\mu }_{p}}\ne 0\] |
| B. | \[{{\mu }_{d}}\ne 0\] and \[{{\mu }_{p}}=0\] |
| C. | \[{{\mu }_{p}}=0\] and \[{{\mu }_{f}}\ne 0\] |
| D. | \[{{\mu }_{d}}\ne 0\] and \[{{\mu }_{f}}\ne 0\] |
| Answer» B. \[{{\mu }_{d}}\ne 0\] and \[{{\mu }_{p}}=0\] | |
| 2176. |
A watch glass containing some powdered substance is placed between the pole pieces of a magnet. Deep concavity is observed at the centre. The substance in the watch glass is |
| A. | iron |
| B. | chromium |
| C. | carbon |
| D. | wood |
| Answer» B. chromium | |
| 2177. |
At a temperatur of \[30{}^\circ C\], the susceptibility of a ferromagnetic material is found to be X. Its susceptibility at \[333{}^\circ C\] is |
| A. | \[\chi \] |
| B. | \[0.5\chi \] |
| C. | \[2\chi \] |
| D. | \[11.1\chi \] |
| Answer» C. \[2\chi \] | |
| 2178. |
Relative permittivity and permeability of a material \[{{\varepsilon }_{r}}\] and \[{{\mu }_{r}}\], respectively. Which of the following values of these quantities are allowed for a diamagnetic material? |
| A. | \[{{\varepsilon }_{r}}=0.5,\,\,\,{{\mu }_{r}}=1.5\] |
| B. | \[{{\varepsilon }_{r}}=1.5,\,\,\,{{\mu }_{r}}=0.5\] |
| C. | \[{{\varepsilon }_{r}}=0.5,\,\,\,{{\mu }_{r}}=0.5\] |
| D. | \[{{\varepsilon }_{r}}=1.5,\,\,\,{{\mu }_{r}}=1.5\] |
| Answer» C. \[{{\varepsilon }_{r}}=0.5,\,\,\,{{\mu }_{r}}=0.5\] | |
| 2179. |
Relative permeability of iron is 5500, then its mangetic susceptibility will be |
| A. | 5501 |
| B. | 5499 |
| C. | \[5500\times {{10}^{7}}\] |
| D. | None of these |
| Answer» C. \[5500\times {{10}^{7}}\] | |
| 2180. |
The magnetic susceptibility of a paramagnetic substances at \[-73{}^\circ \,C\]is 0.0060, then its value at -\[173{}^\circ C\] will be |
| A. | 0.003 |
| B. | 0.012 |
| C. | 0.018 |
| D. | 0.0045 |
| Answer» C. 0.018 | |
| 2181. |
A short bar magnet of magnetic moment \[0.4J\,{{T}^{-1}}\] is placed in a uniform magnetic field of\[0.16\,T\]. The magnet is in stable equilibrium when the potential energy is |
| A. | \[-0.64J\] |
| B. | zero |
| C. | \[-0.082\,J\] |
| D. | \[0.064\,J\] |
| Answer» E. | |
| 2182. |
The B - H curve (i) and (ii) shown in fig associated with |
| A. | (i) diamagnetic and (ii) paramagnetic substance |
| B. | (i) paramagnetic and (ii) ferromagnetic substance |
| C. | (i) soft iron and (ii) steel |
| D. | (i) steel and (ii) soft iron |
| Answer» D. (i) steel and (ii) soft iron | |
| 2183. |
A vibration magnetometer consists of two identical bar magnets placed one over the other such that they are perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is\[{{2}^{5/4}}\]seconds. One of the magnets is removed and if the other magnet oscillates in the same field, then the time period in seconds is |
| A. | \[{{2}^{1/4}}\] |
| B. | \[{{2}^{1/2}}\] |
| C. | 2 |
| D. | \[{{2}^{3/4}}\] |
| Answer» D. \[{{2}^{3/4}}\] | |
| 2184. |
The magnetic needle has magnetic moment \[8.7\times {{10}^{-2}}\,A{{m}^{2}}\] and moment of inertia\[11.5\times {{10}^{-6}}\,kg{{m}^{2}}\]. It performs 10 complete oscillations in 6.70 s, what is the magnitude of the magnetic field? |
| A. | 0.012 T |
| B. | 0.120 T |
| C. | 1.200 T |
| D. | 2.10 T |
| Answer» B. 0.120 T | |
| 2185. |
If the period of oscillation of freely suspended bar magnet in earth's horizontal field H is 4 sec. When another magnet is brought near it, the period of oscillation is reduced to 2s. The magnetic field of second bar magnet is |
| A. | 4H |
| B. | 3H |
| C. | 2H |
| D. | \[\sqrt{3}H\] |
| Answer» B. 3H | |
| 2186. |
A very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained 20 cm away from the centre of the magnet. If the earth's magnetic field (horizontal component) at this point be 0.3 gauss, the magnetic moment of the magnet is |
| A. | \[8.0\times {{10}^{2}}\,e.m.u.\] |
| B. | \[1.2\times {{10}^{3}}\,e.m.u.\] |
| C. | \[2.4\times {{10}^{3}}\,e.m.u.\] |
| D. | \[3.6\times {{10}^{3}}\,e.m.u.\] |
| Answer» C. \[2.4\times {{10}^{3}}\,e.m.u.\] | |
| 2187. |
A freely suspended magnet oscillates with period T in earth's horizontal magnetic field. When a bar magnet is brought near it, such that the magnetic field created by bar magnet is in same direction as earth's horizontal magnetic field, the period decreases to T/2. The ratio of the field of the magnet F to the earth's magnetic field (H) is |
| A. | 1 : 3 |
| B. | 1 : 1 |
| C. | 3 : 1 |
| D. | 0.375694444444444 |
| Answer» D. 0.375694444444444 | |
| 2188. |
A bar magnet of magnetic moment \[4.0\,A-{{m}^{2}}\] is free to rotate about a vertical axis through its center. The magnet is released from rest from east-west position. Kinetic energy of the magnet in north-south position will be \[(H=25\mu T)\] |
| A. | \[{{10}^{-2}}J\] |
| B. | \[{{10}^{-4}}J\] |
| C. | \[{{10}^{-6}}J\] |
| D. | 0 |
| Answer» C. \[{{10}^{-6}}J\] | |
| 2189. |
A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be \[{{H}_{0}}\] and magnetic field inside the loop be H. If a magnet is suspended inside the loop, it makes angle \[\theta \] with H. Then \[\theta \]= |
| A. | \[{{\tan }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\] |
| B. | \[{{\tan }^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\] |
| C. | \[\cos e{{c}^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\] |
| D. | \[{{\cot }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\] |
| Answer» B. \[{{\tan }^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\] | |
| 2190. |
A magnet makes 40 oscillations per minute at a place having magnetic field intensity of\[0.1\times {{10}^{-5}}\,T\]. At another place, it takes 2.5 sec to complete one vibration. The value of earth's horizontal field at that place is |
| A. | \[0.25\times {{10}^{-6}}\,T\] |
| B. | \[0.36\times {{10}^{-6}}\,T\] |
| C. | \[0.66\times {{10}^{-8}}\,T\] |
| D. | \[1.2\times {{10}^{-6}}\,T\] |
| Answer» C. \[0.66\times {{10}^{-8}}\,T\] | |
| 2191. |
Two short magnets with their axes horizontal and perpendicular to the magnetic maridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments \[{{M}_{1}}:{{M}_{2}}\]is |
| A. | 0.170138888888889 |
| B. | 0.684027777777778 |
| C. | 64 : 125 |
| D. | \[2:\sqrt{5}\] |
| Answer» D. \[2:\sqrt{5}\] | |
| 2192. |
The time period of oscillation of a bar magnet suspended horizontally along the magnetic meridian is \[{{T}_{0}}\]. If this magnet is replaced by another magnet of the same size and pole strength but with double the mass, the new time period will be |
| A. | \[\frac{{{T}_{0}}}{2}\] |
| B. | \[\frac{{{T}_{0}}}{\sqrt{2}}\] |
| C. | \[\sqrt{2}{{T}_{0}}\] |
| D. | \[2{{T}_{0}}\] |
| Answer» D. \[2{{T}_{0}}\] | |
| 2193. |
At a place on earth, horizontal component of earth's magnetic field is \[{{B}_{1}}\] and vertical component of earth's magnetic field is \[{{B}_{2}}\]. If a magnetic needle is kept vertical, in a plane making angle \[\alpha \] with the horizontal component of magnetic field, then square of time period of oscillation of needle when slightly distributed is proportional to |
| A. | \[\frac{1}{\sqrt{{{B}_{1}}\,\cos \,\alpha }}\] |
| B. | \[\frac{1}{\sqrt{{{B}_{2}}}}\] |
| C. | \[\frac{1}{\sqrt{{{({{B}_{1\,}}\cos \,\alpha )}^{2}}+B_{2}^{2}}}\] |
| D. | infinite |
| Answer» D. infinite | |
| 2194. |
A short bar magnet is placed in the magnetic meridian of the earth with North Pole pointing north. Neutral points are found at a distance of 30 cm from the magnet on the East-West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in \[A{{m}^{2}}\] is close to: (Given \[\frac{{{\mu }_{0}}}{4\pi }={{10}^{-7}}\] in SI units and \[{{B}_{H}}\]=Horizontal component of earth's magnetic field \[=3.6\times {{10}^{-5}}\,tesla\]) |
| A. | 14.6 |
| B. | 19.4 |
| C. | 9.7 |
| D. | 4.9 |
| Answer» D. 4.9 | |
| 2195. |
A 10 cm long bar magnet of magnetic moment \[1.34\,A{{m}^{2}}\] is placed in the magnetic meridian with its south pole pointing geographical south. The neutral point is obtained at a distance of 15 cm from the centre of the magnet. Calculate the horizontal component of earth's magnetic field. |
| A. | \[0.12\times {{10}^{-4}}\,T\] |
| B. | \[0.21\times {{10}^{-4}}T\] |
| C. | \[0.34\times {{10}^{-4}}T\] |
| D. | \[0.87\times {{10}^{-7}}T\] |
| Answer» D. \[0.87\times {{10}^{-7}}T\] | |
| 2196. |
A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled, the deflection will |
| A. | increase |
| B. | decrease |
| C. | remain same |
| D. | any of these |
| Answer» D. any of these | |
| 2197. |
Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magnetrons (1 Bohr magnetos \[=9.27\times {{10}^{-24}}\,A-{{m}^{2}}\]). The density of atoms in iron is \[8.52\times {{10}^{28}}\,atoms/{{m}^{3}}.\]Find the maximum magnetic moment per unit volume. |
| A. | \[1.5\times {{10}^{2}}\,A/m\] |
| B. | \[1.58\times {{10}^{6}}\,A/m\] |
| C. | \[1.2\times {{10}^{5}}\,A/m\] |
| D. | \[1.3\times {{10}^{6}}\,A/m\] |
| Answer» C. \[1.2\times {{10}^{5}}\,A/m\] | |
| 2198. |
Let V and H be the vertical and horizontal components of earth's magnetic field at any point on earth. Near the North Pole |
| A. | V>>H |
| B. | V<<H |
| C. | V=H |
| D. | V=H=0 |
| Answer» B. V<<H | |
| 2199. |
A torque of \[{{10}^{-\,5}}\,Nm\] is required to hold a magnet at \[90{}^\circ \] with the horizontal component H of the earth's magnetic field. The torque to hold it at \[30{}^\circ \] will be |
| A. | \[5\times {{10}^{-6}}\,Nm\] |
| B. | 5 Nm |
| C. | \[\frac{1}{3}\times {{10}^{-5}}\,Nm\] |
| D. | \[5\sqrt{3}\times {{10}^{-6}}\,Nm\] |
| Answer» B. 5 Nm | |
| 2200. |
A bar magnet 8 cms long is placed in the magnetic merdian with the N-pole pointing towards geographical north. Two netural points separated by a distance of 6 cms are obtained on the equatorial axis of the magnet. If horizontal component of earth's field \[=3.2\times {{10}^{-5}}T\], then pole strength of magnet is |
| A. | \[5\,ab-amp\times cm\] |
| B. | \[10\,ab-amp\times cm\] |
| C. | \[2.5\,ab-amp\times cm\] |
| D. | \[20\,ab-amp\times cm\] |
| Answer» B. \[10\,ab-amp\times cm\] | |