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CBSE XII
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Physics
Physics
Electric charges and fields
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Why do we prefer steel or alnico for making permanent magnets ?
cbse
class12
physics
ch-5
sec-a
q77
ncert
medium
asked
Jul 21, 2015
by
meena.p
1
answer
A coil of 200 turns has a cross -sectional area $900 mm^2$ . if carries a current of 2 ampere . The plane of the coil is perpendicular to a uniform magnetic field of $0.5 \;T$ Calculate the magnetic moment of the coil.
cbse
class12
physics
ch-5
sec-a
q75
medium
asked
Jul 21, 2015
by
meena.p
1
answer
State curies's law in magnetism?
cbse
class12
physics
ch-5
sec-a
q75
medium
asked
Jul 21, 2015
by
meena.p
1
answer
A magnetic needle of magnetic moment $4.8 \times 10^{-2}\;JT^{-1}$ is placed at $30^{\circ}$ with the direction of uniform magnetic field of magnitude $3 \times 10^{-2} \;T$ Calculate the torque acting on the needle
cbse
class12
physics
ch-5
sec-a
q74
ncert
medium
asked
Jul 21, 2015
by
meena.p
1
answer
A magnetized needle is placed $30^{\circ}$ with direction of uniform magnetic field of intensity $3 \times 10^{-2}\;T$ The torque acting on the needle is $7.2 \times 10^{-4} \;J$ Calculate the magnetic moment of the needle .
cbse
class12
physics
ch-5
sec-a
q73
ncert
medium
asked
Jul 20, 2015
by
meena.p
1
answer
The vertical component of earth magnetic field at a plane is $\large\frac{1}{\sqrt 3}$ times the horizontal component. What is the value of angle of dip at this place ?
cbse
class12
physics
ch-5
sec-b
q72
ncert
medium
asked
Jul 20, 2015
by
meena.p
1
answer
A magnetic needle of a magnetic moment $60 Am^2$ is placed at a place . The needle points towards the geographical north. using the data given below, find the value of declination at the point . Horizontal component of earth magnetic field $=40 \times 10^{-6}wb m^{-2}$ and torque experienced by the needle $=1.2 \times 10^{-3}Nm$
cbse
class12
physics
ch-5
sec-b
q71
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
What is the SI unit for magnet flux and magnetic field strength
cbse
class12
physics
ch-5
sec-a
q70
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
Name any two dia magnetic substance
cbse
class12
physics
ch-5
sec-a
q68
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
State tangent law in magnetism.
cbse
class12
physics
ch-5
sec-a
q67
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
What is the reduction factor of galvanometer . The amount of of current required to produce $45^{\circ}$ deflection in a galvanometer is defined as it reduction factor.
cbse
class12
physics
ch-5
sec-a
q66
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
How does the magnetic moment of each part of the bar magnet . change if it is cut into two equal pieces along its length ?
cbse
class12
physics
ch-5
sec-a
q65
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
How does the pole strength of each part of bar magnet change if it is cut into equal piece along its length ?
cbse
class12
physics
ch-5
sec-a
q64
ncert
medium
asked
Jul 20, 2015
by
meena.p
1
answer
How does the magnetic moment of each part of the bar magnet change it is cut into two equal piece transverse to its length ?
cbse
class12
physics
ch-5
sec-a
q63
ncert
medium
asked
Jul 20, 2015
by
meena.p
1
answer
How does the pole strength of each part of a bar magnet change if it is cut into two equal pieces transverse to its length ?
cbse
class12
physics
ch-5
sec-a
q62
ncert
medium
asked
Jul 20, 2015
by
meena.p
1
answer
Where on the earth's surface is the value of angle of dip maximum ?
cbse
class12
physics
ch-5
sec-a
q61
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
What is the value of the horizontal component of the earth 's magnetic field at magnetic poles?
cbse
class12
physics
ch-5
sec-a
q60
ncert
easy
asked
Jul 20, 2015
by
meena.p
1
answer
There are two current planer coils made each from identical wires of length L. $C_1$ is circular coil (radius R) and $C_2$ is square (side a). They are so constructed that they have same frequency of oscillation when they are placed in the same uniform magnetic field B and carry same current. Find a in term of R.
cbse
class12
physics
ch-5
sec-a
q59
ncert
difficult
asked
Jul 20, 2015
by
meena.p
1
answer
Consider the plane S formed by the dipole axis and the axis of earth . Let P be point of intersection of the geographical and magnetic equators. Obtain the declination and dip angles at P and Q.
cbse
class12
physics
ch-5
sec-a
q58
ncert
easy
asked
Jul 16, 2015
by
meena.p
1
answer
Assume the dipole model for earth's magnetic field B which is given by $B_v$ =Vertical component of magnetic field $=\large\frac{\mu_0}{4 \pi}.\frac{2m \cos \theta}{r}$ $B_H$= Horizontal component of magnetic field $\qquad= \large\frac{\mu_o}{4 \pi} \frac{\sin \theta m}{r^3}$ $\theta= 90^{\circ}$- latitude as measured from magnetic equator . Find loci of points for which dip angle is $\pm 45^{\circ}$
cbse
class12
physics
ch-5
sec-a
q57
ncert
medium
asked
Jul 16, 2015
by
meena.p
1
answer
Assume the dipole model for earth's magnetic field B which is given by $B_v$ =Vertical component of magnetic field $=\large\frac{\mu_0}{4 \pi}.\frac{2m \cos \theta}{r}$ $B_H$= Horizontal component of magnetic field $\qquad= \large\frac{\mu_o}{4 \pi} \frac{\sin \theta m}{r^3}$ $\theta= 90^{\circ}$- latitude as measured from magnetic equator . Find loci of points for which clip angle is zero.
cbse
class12
physics
ch-5
sec-b
q56
ncert
medium
asked
Jul 16, 2015
by
meena.p
1
answer
Assume the dipole model for earth's magnetic field B which is given by $B_v$ =Vertical component of magnetic field $=\large\frac{\mu_0}{4 \pi}.\frac{2m \cos \theta}{r}$ $B_H$= Horizontal component of magnetic field $\qquad= \large\frac{\mu_o}{4 \pi} \frac{\sin \theta m}{r^3}$ $\theta= 90^{\circ}$- latitude as measured from magnetic equator . Find loci of points for which $|B|$ is minimum
cbse
class12
physics
ch-5
sec-a
q55
ncert
medium
asked
Jul 16, 2015
by
meena.p
1
answer
A bar magnet of magnetic m and moment of inertia I (about center , perpendicular to length ) is cut into two equal pieces, perpendicular to length . Let T be the period of oscillations of the original magnet about an axis . through the mid -point , perpendicular to length , in a magnetic field B. What would be the similar period $T^1$ for each piece?
cbse
class12
physics
ch-5
sec-a
q54
ncert
difficult
asked
Jul 16, 2015
by
meena.p
1
answer
A proton has spin and magnetic moment just line an electron , Why then its effect is neglected in magnetism of materials?
cbse
class12
physics
ch-5
sec-a
q54
ncert
medium
asked
Jul 16, 2015
by
meena.p
1
answer
A magnetic moment $\mu _s$ and $\mu_i$ associated with the intrinsic spin angular momentum $S$ and orbital momentum l respectively , of an electron are predicted by quantum theory (and verified experimentally to a high accuracy ) to be given by $\mu_s= -\bigg(\large\frac{e}{m} \bigg)$$s; \mu_e =-\bigg(\large\frac{e}{2m}\bigg)$$l$ Which of these relations is in accordance with the result expected classically ? outline the deviation of the classical result ?
cbse
class12
physics
ch-5
sec-a
q53
ncert
medium
asked
Jul 16, 2015
by
meena.p
1
answer
A rowland ring of mean radius $15\;cm$ has $3500$ turns of wire wound on a ferro magnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetizing current of $12.A$?
cbse
class12
physics
ch-5
sec-a
q52
ncert
medium
asked
Jul 15, 2015
by
meena.p
1
answer
A sample of paramagnetic salt contains $2.0 \times 10^{24} $ atomic dipoles each of dipole moment $1.5 \times 10^{-23}\; J/T$. the sample is placed under a homogeneous magnetic field of $0.64 \;T$ and colled to a temperature of $4.2 \;K$ . The degree of magnetic saturation achieved is equal to $15\%$ What is the total dipole moment of the sample for a magnetic field of $0.98 \;T$ and a temperature of $2.8 \;k$? (assume curies's law)
cbse
class12
physics
ch-5
sec-a
q51
ncert
difficult
asked
Jul 15, 2015
by
meena.p
1
answer
A mono energetic $(18\;kev)$ electron beam initially in the horizontal direction is subjected to a horizontal magnetic field of $0.4\;G$ normal to the initial direction . Estimate the up or down deflection of the beam over a distance of $30\;cm(m_e=9.11 \times 10^{-19}\;c)$
cbse
class12
physics
ch-5
sec-a
q50
ncert
medium
asked
Jul 15, 2015
by
meena.p
1
answer
A magnetic dipole is under the influence of two magnetic fields. The angle between the field direction is $60^{\circ}$ and one of the field has a magnitude of $1.2 \times 10^{-2}\;T$ If the dipole comes to stable equilibrium to an angle of $15^{\circ}$ with this field , What is the magnitude of the other field ?
cbse
class12
physics
ch-5
sec-a
q49
ncert
difficult
asked
Jul 15, 2015
by
meena.p
1
answer
The current in the coil is reversed and the coil is rotated about its vertical axis by an angle of $90^{\circ}$ in the anti clock wise sense looking from above . Predict the direction of the needle. Take the negative declination at the places to be zero.
cbse
class12
physics
ch-5
sec-a
q47
ncert
easy
asked
Jul 15, 2015
by
meena.p
1
answer
A compass needle free to turn in a horizontal plane is placed at the center of circulaum coil of $30$ turns and radius $12\;cm$ . The coil is in a vertical plane making an angle of $45^{\circ}$ with the magnetic medician. when the current in the coil is $0.35\;A$ the needle points west to East. Determine the horizontal component of the earth's magnetic field at the location .
cbse
class12
physics
ch-5
sec-a
q47
ncert
medium
asked
Jul 15, 2015
by
meena.p
1
answer
A telephone cable at a place has four long straight horizontal wires carrying a current of $1.0 \;A$ in the same direction east to west. The earth magnetic field at the place is $ 0.39 \;G$ and the angle of dip is $35^{\circ}$. The magnetic declination is nearly zero. what are the resultant magnetic fields at points $ 4.0 \;cm$ above the cable ?
cbse
class12
physics
ch-5
sec-a
q46
ncert
medium
asked
Jul 15, 2015
by
meena.p
1
answer
A telephone cable at a place has four long straight horizontal wires carrying a current of $1.0 \;A$ in the same direction east to west. The earth magnetic field at the place is $ 0.39 \;G$ and the angle of dip is $35^{\circ}$. The magnetic declination is nearly zero. what are the resultant magnetic fields at points $ 4.0 \;cm$ below the cable ?
cbse
class12
physics
ch-5
sec-a
q45
ncert
difficult
asked
Jul 15, 2015
by
meena.p
1
answer
A long straight horizontal cable carries a current of $2.5 \;A$ in the direction $10^{\circ}$ south of went to $10^{\circ}$ north of east . The magnetic meridian of the place happens to be $10^{\circ}$ west of the geographic meridian . The earth's magnetic field at the location is $ 0.33 \;G$ and the angle of the dip is zero. Locate the line of neutral points (ignore the thickness of the cable ). (At neutral point magnetic field due to current - carrying cable is equal and opposite to the horizontal component of earth's magnetic field )
cbse
class12
physics
ch-5
sec-a
q43
ncert
medium
asked
Jul 15, 2015
by
meena.p
1
answer
A certain region of space is to be shielded from magnetic fields. Suggest a method.
cbse
class12
physics
ch-5
sec-a
q43
ncert
medium
asked
Jul 14, 2015
by
meena.p
1
answer
What kind of ferromagnetic material is used for coating magnetic tapes in casette player or for building memory stores in a modern computer ?
cbse
class12
physics
ch-5
sec-a
q42
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
A system displaying a hysteresis loop such as a ferromagnet, is a device for storing memory . explain the meaning of this statement.
cbse
class12
physics
ch-5
sec-a
q41
ncert
medium
asked
Jul 14, 2015
by
meena.p
1
answer
The hysteresis loop of a soft iron piece has a much smaller are than that of a carbon steel piece . If the material is to go through repeated cycle of magnetization , Which piece will dissipate greater heat energy ?
cbse
class12
physics
ch-5
sec-a
q40
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Explain quantitative on the basis of domain picture the reversibility of a ferromagnet?
cbse
class12
physics
ch-5
sec-a
q39
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Would the maximum possible magnetization of a para magnetic sample be of the same order of magnitude as the magnetization of a ferromagnet.
cbse
class12
physics
ch-5
sec-a
q38
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
If a torrid uses Bismuth for its core, will the field in the core be (slightly ) greater or (slightly ) less than when the core is empty ?
cbse
class12
physics
ch-5
sec-a
q37
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Is the permeability of a ferromagnetic material independent of the magnetic field ? If not, is it more for lower or higher fields?
cbse
class12
physics
ch-5
sec-a
q36
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Magnetic field lines are always nearly normal to the surface of a force magnet at every point. (This fact is analogous to the static electric field lines being normal to the surface of a conductor at every Point ) Why?
cbse
class12
physics
ch-5
sec-b
q35
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Why is diamagnetism, in contract , almost independent of temperature ?
cbse
class12
physics
ch-5
sec-b
q34
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
Why does a para magnetic sample display greater magnetization (for the same magnetizing field) when colled ?
cbse
class12
physics
ch-5
sec-b
q33
ncert
easy
asked
Jul 14, 2015
by
meena.p
1
answer
A short bar magnet of magnetic moment $5.25 \times 10^{-2}\;J/T$ is placed with its axis perpendicular to the earth's field direction . At what distance from the center of the magnet , the resultant field is inclined at $45^{\circ}$ with earth's field at the place is given to be $0.42\;G$ Ignore the length of the magnet in companion to the distance involved
cbse
class12
physics
ch-5
sec-b
q32
ncert
medium
asked
Jul 14, 2015
by
meena.p
1
answer
A short bar magnet of magnetic moment $5.25 \times 10^{-2}\;J/T$ is placed with its axis perpendicular to the earth's field direction . At what distance from the center of the magnet , the resultant field is inclined at $45^{\circ}$ with earth's field on its normal bisector. Magnitude of the earth's field at the place is given to be $0.42\;G$ Ignore the length of the magnet in companion to the distance involved
cbse
class12
physics
ch-5
sec-b
q31
ncert
difficult
asked
Jul 14, 2015
by
meena.p
1
answer
A short bar magnet placed in a horizontal plane has its axis aligned along the magnet north - south direction . Null points are found on the axis of the of the magnet at $14\;cm$ from the center of the magnet . The earth magnetic field at the place is $0.36\;G$ and the cycle of dip is zero. If the bar magnet is turned around by $180^{\circ}$Where will the new null points be located ?
cbse
class12
physics
ch-5
sec-a
q30
ncert
difficult
asked
Jul 13, 2015
by
meena.p
1
answer
A short bar magnet placed in a horizontal plane has its axis aligned along the magnet north - south direction . Null points are found on the axis of the of the magnet at $14\;cm$ from the center of the magnet . The earth magnetic field at the place is $0.36\;G$ and the cycle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null - point (14 cm) from the centre of the magnet?
cbse
class12
physics
ch-5
sec-c
q29
ncert
medium
asked
Jul 13, 2015
by
meena.p
1
answer
A short magnet has a magnetic moments of $0.48\;J/T$. give the direction and magnitude of the magnetic field produced by the magnet of a distance of $10\; cm$ from the center of the magnet on the equatorial lines (normal bisector ) of the magnet .
cbse
class12
physics
ch-5
sec-a
q28
ncert
medium
asked
Jul 13, 2015
by
meena.p
1
answer
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