Recent questions in Magnetism and matter

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 ?

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 $12.A$?

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)

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 $30\;cm(m_e=9.11 \times 10^{-19}\;c)$

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 ?

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.

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 .

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 ?

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 ?

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 )

asked Jul 15, 2015 by meena.p

1 answer

A certain region of space is to be shielded from magnetic fields. Suggest a method.

asked Jul 14, 2015 by meena.p

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What kind of ferromagnetic material is used for coating magnetic tapes in casette player or for building memory stores in a modern computer ?

asked Jul 14, 2015 by meena.p

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A system displaying a hysteresis loop such as a ferromagnet, is a device for storing memory . explain the meaning of this statement.

asked Jul 14, 2015 by meena.p

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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 ?

asked Jul 14, 2015 by meena.p

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Explain quantitative on the basis of domain picture the reversibility of a ferromagnet?

asked Jul 14, 2015 by meena.p

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Would the maximum possible magnetization of a para magnetic sample be of the same order of magnitude as the magnetization of a ferromagnet.

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 ?

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?

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?

asked Jul 14, 2015 by meena.p

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Why is diamagnetism, in contract , almost independent of temperature ?

asked Jul 14, 2015 by meena.p

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Why does a para magnetic sample display greater magnetization (for the same magnetizing field) when colled ?

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

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

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 ?

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?

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 .

asked Jul 13, 2015 by meena.p

1 answer

At a certain location in Africa , a component points $12^{\circ}$ west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points $60^{\circ}$ and above the horizontal. The horizontal component of the earth's field is measured to be $0.16 \;G$ Specify the direction and magnitude of the earth's field at the location .

asked Jul 13, 2015 by meena.p

1 answer

A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at $22^{\circ}$ with the horizontal. The horizontal component of the earth's magnetic field at the plane is known to be $0.35 \;G$ . Determine the magnetic of the earth's magnetic field at the place.

asked Jul 13, 2015 by meena.p

1 answer

A circular coil of 16 turns and radius $10\;cm$ carrying a current of $0.75 \;A$ rests with its plane normal to an external field of magnitude $5.0 \times 10^{-2}\;T$ The coil is free to turn about an axis in its plane perpendicular to the field direction , When the coil is turned slightly and released it oscillates about its stable equilibrium with a frequency of $2.0 m/s$ . What is the moment of inertia of the coil about its axis of rotation ?

asked Jul 13, 2015 by meena.p

1 answer

A closely wound solenoid of $2000$ turns and area of cross section $1.6 \times 10^{-4}m^2$, carrying a current of $4.0\;A$ is suspended through its center allowing it to turn in a horizontal plane. What are the force and torque on the solenoid, if a uniform horizontal magnetic field of $7.5 \times 10^{-2}\;T$ is setup at an angle of $30^{\circ}$ with the axis of solenoid ?

asked Jul 13, 2015 by meena.p

1 answer

A closely wound solenoid of $2000$ turns and area of cross section $1.6 \times 10^{-4}m^2$, carrying a current of $4.0\;A$ is suspended through its center allowing it to turn in a horizontal plane. What is the magnetic moment associated with the solenoid ?

asked Jul 10, 2015 by meena.p

1 answer

A bar magnet of magnetic moment $1.5\;J/T$ lies aligned with the direction of a uniform magnetic field of $0.22\;T$ What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment, opposite to the field direction ?

asked Jul 10, 2015 by meena.p

1 answer

A bar magnet of magnetic moment $1.5\;J/T$ lies aligned with the direction of a uniform magnetic field of $0.22\;T$ What is the torque on the magnet when the magnet aligns normal to the field direction ?

asked Jul 10, 2015 by meena.p

1 answer

A bar magnet of magnetic moment $1.5\;J/T$ lies aligned with the direction of a uniform magnetic field of $0.22\;T$ What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment, opposite to the field direction ?

asked Jul 10, 2015 by meena.p

1 answer

A bar magnet of magnetic moment $1.5\;J/T$ lies aligned with the direction of a uniform magnetic field of $0.22\;T$

asked Jul 10, 2015 by meena.p

1 answer

If the solenoid in the above question is free to turn about the vertical direction and a uniform magnetic field of $0.25 \;T$ is applied , what is the magnitude of torque on the solenoid when its axis makes an angle of $30^{\circ}$ with the direction of applied field.

asked Jul 10, 2015 by meena.p

1 answer

A closely wound solenoid of 800 turns and area of cross section $2.5 \times 10^{-4} \;m^2$ carries a current of $3.0 \;A$Explain the same in which the solenoid acts like a bar magnet . What is its associate magnetic moment ?

asked Jul 10, 2015 by meena.p

1 answer

A short bar magnet of magnetic moment $m= 0.32 \;J/T$. is placed in a uniform magnetic field of $0.15 \;T$. If the bar is free to rotate in the plane of the field, Which orientation would correspond to its unstable equilibrium ? What is the potential energy of the magnet?

asked Jul 10, 2015 by meena.p

1 answer

A short bar magnet of magnetic moment $m= 0.32 \;J/T$. is placed in a uniform magnetic field of $0.15 \;T$. If the bar is free to rotate in the plane of the field, Which orientation would correspond to its stable equilibrium ? What is the potential energy of the magnet?

asked Jul 10, 2015 by meena.p

1 answer

A short bar magnet with its axis at $30^{\circ}$ with a uniform external magnetic field of $0.25\;T$ experiences a forque a magnitude equal to $4.5 \times 10^{-2}\;J$ What is the magnitude of magnetic moment of the magnet?

asked Jul 10, 2015 by meena.p

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Instellar space has an excellently weak magnetic field of the order of $10^{-12}\;T$ can such a weak field be of any significant consequence. Explain

asked Jul 10, 2015 by meena.p

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The earth's field departs from its dipole shape substantially at large distance (greater than about 30,000 km) What agencies may be responsible for this distortion ?

asked Jul 10, 2015 by meena.p

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The earth may have reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth field in such distant past ?

asked Jul 9, 2015 by meena.p

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The charged currents in the outer conducting regions of the earth core are thought to be responsible for earth's magnetism. What might be the battery (ie the cource of energy ) to sustain these currents ?

asked Jul 9, 2015 by meena.p

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The earth's core is known to contain iron. yet geologists do not regard this as a source of the earth mergnetisum . Why ?

asked Jul 9, 2015 by meena.p

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The earth's magnetic field from point to point in space . Does it also charge with time ? If so on what time scale does it change appreciably ?

asked Jul 9, 2015 by meena.p

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Geologist claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different direction . How is such a thing possible at all ?

asked Jul 9, 2015 by meena.p

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In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole ?

asked Jul 9, 2015 by meena.p

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The earth's field it is claimed roughly approximately the field due to a dipole of magnetic moment $8 \times 10^{22}J/T$ located at its centre. Check the order of magnitude of this number is same way

asked Jul 9, 2015 by meena.p

1 answer

If you made a map of magnetic field line at Melbourne in Australian, would the line seem to go into the ground or come out the ground ?

asked Jul 9, 2015 by meena.p

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