Class 12 Physics CBSE Pattern Questions Bank
Ch. 5 Magnetism and Matter & Ch.6 Electromagnetic Induction
SECTION ‘A’ (1 Marks)
Q.1 Earth’s magnetic field and angle of dip at a point is 0.3 G and 30 degree. calculate the vertical component of Earth’s magnetic field.
Q.2 State lenz Law.
Q.3 A plot of magnetic flux versus current is shown in the figure for two inductors A and
B which of the two has a large self inductance.
Q.4 Write one important property of paramagnetic material
Q.5 Is the steady current the only source of the magnetic field? justify your answer
Q.6 Predict the direction of induced current in the metal rings 1 and 2 lying in the same
plane where current I in the wire is increasing steadily. In figure
Q.7 How does the mutual inductance of a pair of of coils change when (a) the distance between the points is increased and (b) the number of turns in the coil is increased
Q.8 The susceptibility of a magnetic material is – 4.2 x 10^-6. Name the type of the magnetic materials it represents.
Q.9 Name any two applications where eddy Currents are used to advantage.
Q.10 Draw the pattern of magnetic field lines for a bar magnet.
Q.11 State curie’s law
Q.12 State Faraday’s law of electromagnetic induction.
Q.13 Draw a labelled diagram showing the magnetic elements of the earth.
Q.14 Lenz’s law is used to find the direction of
a) Electric field
b) force
c) Induced current
d) Electrostatic force
Q.14 State curie’s law. How does the susceptibility and the relative permeability of paramagnetic substances vary with the temperature.
Q.15 A metallic piece gets heated when surrounded by carrying high frequency alternating current. Why ?
Q.16 Why the SI unit of magnetism is A/m ? Give a short explanation on it.
Q.17 Name any three applications where eddy currents are used to advantage.
Q.18 Obtain a relationship between the charge flowing through the circuit and the change in magnetic flux.
Q.19 If Magnetic monopoles existed, how would Gauss’s law of magnetism be modified?
Q.20 A long straight current carrying wire passes normally through the centre of a circular loop. If the current through the wire increases there will be an induced emf in the loop.
Q.21 Where on the surface of earth is the angle of dip zero ?
Q.22 What is electromagnetic induction ?
Q.23 Current flows through a circular loop. Depict the north and South Pole of its equivalent magnetic dipole.
SECTION ‘B’ (2 marks)
Q.1 One metre long metallic rod is rotated with an angular frequency of 400 rad/second about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic raig. A constant and uniform magnetic field of 0.5 Tesla parallel to the axis exists everywhere. calculate the EMF developed between the centre of the ring.
Q.2 A bar magnet of magnetic moment M is aligned parallel to the direction of a uniform magnetic field B. what is the work done to turn the magnet so as the align its magnetic moment.
(i) opposite to the field direction?
(ii) normal to the field direction?
Q.3 A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its North tip pointing down at 22 degree with the horizontal. The horizontal component of the Earth’s magnetic field at that place is known to be 0.35 G. Determine the magnitude of the Earth’s magnetic field at the place is known to be 0.35 G. Determine the magnitude of the Earth’s magnetic field at that place.
4 (a) Define self inductance of a coil.
(b) Show the magnetic potential energy required to build up current 1 in coil of self inductance L is given by LI^2/2 .
Q.5 A compass needle free to turn in the vertical plane orients itself vertically at a certain place on the earth
(i) the horizontal component of Earth’s magnetic field
(ii) the angle of dip
Q.6 A horizontal conducting rod 10 m long extending from east to west is falling with a speed 5 m/s at right angle to the horizontal component of the Earth’s magnetic field 0.3 x 10^-4 Wb/m2 . Find the instantaneous value of the emf induced in the rod.
Q.7 A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its Northern tip down at 60 degree with the horizontal. The horizontal component of Earth’s magnetic field at the place is known to be 0.4 G. Determine the magnitude of Earth’s magnetic field at the place.
Q.8 a) Obtain the expression for the magnetic energy stored in a solenoid in terms of the magnetic field B, area A and length L of the solenoid.
b) How is the magnetic energy per unit volume compared with the electrostatic energy per unit volume stored in a parallel plate capacitor?
Q.9 The susceptibility of a magnetic material is -2.6 x 10-5 . Identify the type of magnetic material and state its two properties.
Q.10 Define the magnetic susceptibility of a material . Name two elements, one having positive susceptibility.
Q.11 The magnetic flux through a coil perpendicular to its plane and directed into the paper is varying according to the relation Ф = ( 2t^2 + 4t + 6) Wb/m^2. The emf induced in the loop at t = 4 second is…
OR
The self inductance of a coil having 400 terms is 10 mH. The magnetic flux through the cross section of the coil corresponding to current 2 mA is
Q.12 a) The vertical component of Earth’s magnetic field at a place is 3 times horizontal component of value of the value of angle of dip at this place is
b) why is the core of electromagnet made of ferromagnetic materials ?
Q.13 The current in a coil of self inductance 5 mH changes from 2.5 to 2 A in 0.1 second. calculate the value of self induced emf.
Q.14 A short bar magnet placed with its axis of 30 degree with the uniform external magnetic field of 0.25 Tesla experiences a torque of magnitude equal to 4.5 x 10^-2 J. what is the magnitude of magnetic moment of the magnet?
Q.15 A horizontal straight wire 10 cm long extending from east to west falling with a speed of 5 metre per second at the right angle of the horizontal component of the Earth’s magnetic field 0.3 x 10– 4 wb/m^2 .
a) what is the instantaneous value of the cell induced in the wire?
b) what is the direction of emf.
Q.16 A circular coil of wire consisting of 100 turns each of radius 8 cm carries a current of 0.4 A. what is the magnitude of the magnetic field B at the centre of the coil ?
Q.17 A closely wound solenoid of 800 turns and area of cross section 2.5 x 10^- 4 m^2 carries a current of 3 A. Explain the sense in which the solenoid acts like a bar magnet. what is its associated magnetic moment ?
Q.18 A 1 cm long metallic rod is rotated with an angular frequency of 400 rad/s about an axis normal to the rod passing through the one end. The other end of the rod is in contact with the circular metallic ring. A constant and uniform magnetic field of 0.5 Tesla parallel to the axis exist everywhere. calculate the emf developed between the centre and the ring.
Q.19 a) Difference between self inductance and mutual inductance
b) State lenz Law
c) susceptibility is denoted as
Q.20 Current in a circuit falls from 5 to 0 A in 0.01. If an average EMF of 200 V induced give an estimate of the self inductance of the circuit.
Q.21 Given an analogue of the following formula from the electrostatic to magnetism
| Electrostatic | Magnetism | |
| equatorial field for short dipole | ||
| exit field for short dipole | ||
| external field torque | ||
| external field energy |
Q.22 The earth’s field it is is claimed roughly approximate that the field due to the dipole at the magnetic moment 8 x 10^22 J/T located at its centre. Check the of the magnitude of this number in same way . (R of Earth = 6.4 x 10^6 m )
Q.23 Out of two magnetic materials, A has relative permeability slightly greater than unity while B has less than unity. Identify the nature of the materials A and B . Will their susceptibilities be positive or negative?
Q.24 The magnetic field B and magnetic intensity of a material are found to be 1.6 Tesla and 1000 A/m respectively. calculate the relative permeability (μr) and the susceptibility ( χ) of the material.
Q.25 Two identical loops one of the copper and other of the aluminium are rotated with the same angular speed in the same magnetic field. Compare (i) the induced EMF and
(ii) the current produced in the two coils . justify your answer.
SECTION ‘ C‘ (Marks 3)
1. Using Ampere’s circuital law . Derive an expression for the magnetic field along the axis of a toroidal solenoid.
2. A rectangular wire loop of sides 8 cm and 2cm with a small cut is moving out of a region of the uniform magnetic field of magnitude 0.3 Tesla directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm/s in a direction normal to the the
a) longer side
b) shorter side of the loop ? For how long does the induced voltage last in each case?
3. A solenoid has a core of material with relative permeability 400. The windings of the solenoid area insulated from the core and carry a current of 2 A. If the number of turns is 1000 per metre calculate
a) H (b) M (c) B (d) magentizing current
Q.4 A conducting rod PQ of length 20 cm and resistance 0.1 ohm resistance to smooth parallel rails of negligible resistance AA’ and CC’ . It can slide on the rails and the arrangement is positioned between the poles of permanent magnet producing uniform magnetic field B = 0.4 Tesla. The rails, the rod and the magnetic field are in the three mutually perpendicular direction as shown in the figure. If the ends A and C of the rails are short circuled find the
(i) the external force required to move the rod with uniform velocity V= 10 cm/s and
(ii) power required to do so
Q.5 A short bar magnet of magnetic moment m = 0.32 J/T is placed in a uniform magnetic field of 0.15 Tesla. if the bar is free to rotate in the Plane of the field which orientation would you respond to its
(a) Stable
(b) unstable equilibrium
what is the potential energy of the magnet in each cases?
Q.6 A jet plane is travelling towards the west at a speed of 1800 km per hour what is the voltage difference between developed between the ends of the wing having a span of 25 m if the earths magnetic field at the location has a magnitude 5 x 10^-4 T and dip angle is 30 degree.
Q.7 A circular coil of radius 8.5 cm and 50 turns per cm is rotated about its vertical diameter with an angular speed of 10 rad per second in a uniform horizontal magnetic field of magnitude 5 x 10^-4 T. obtain the maximum and average EMF induced in the coil. If the coil forms a closed loop of resistance 5 ohm. calculate the maximum value of the current in the coil. calculate the average power loss due to the joule heating. where does this power come from?
Q.8 A short bar magnet of magnetic moment 6.2 x 10^-6 J/T is placed with its axis perpendicular the earth’s magnetic field direction. At what distance from the centre of the magnet the resultant field is inclined at 45 degree with the field and magnitude of earths field at the place is 0.5 G.
(a) it’s normal bisector
(b) its axis
Q.9 Define a) magnetic declination b) magnetic dip c ) mention the SI unit of magnetisation
Q.10 state and explain Gauss law in magnetism
Q.11 Define the term self inductance of a solenoid. obtain the expression for the magnetic energy stored in an inductor of self inductance L build up a current I through it.
Q.12 A horizontal straight wire 10m long extending from east to west is falling with a speed of 5 metre per second at right angles to the horizontal component of the Earth’s magnetic field 0.3 x 10^-4 Weber per square metre.
(i) what is the instantaneous value of the EMF induced in the wire?
(ii) what is the direction of EMF?
(iii) which end of the wire is at the higher electrical potential?
Q.13 Derive the formula of self inductance of long solenoid.
Q.14 A rectangular as wire loop of side 8 cm and 2 cm with the small cut is moving out of the region of uniform magnetic field of magnetic field 0.3 Tesla directed normal to the loop what is the EMF developed across the velocity of the loop is 1 cm per second in a direction normal to the
a) the longest side
b) shorter side of the loop? how long does the induced voltage last in such case?
Q.15 The currents flowing in the two coils of the self inductance L1 = 16 mH
and L2 = 12 mH are increasing at the same rate if the power supplied to the two coils are equal and find the ratio of
(i) induced voltage
(ii) the currents and
(iii) Energy stored in the two coils at a given instant
Q.16 An iron rod of 0.5 cm^2 area of cross section is subjected to a magnetising field of 1200 A/m. if the susceptibility of iron is 599 . Calculate (i) μ (ii) B and (iii) Φ produced
SECTION ‘ D‘ (Marks 5)
Q.1 In a step up transformer, the transformation ratio is 100 .The primary voltage is 200 volt and input its 1000 watt. The number of turns in the primary is 100. Calculate
a) Number of turns in the secondary
b) current in the primary
c) The voltage across the secondary
d) current in the secondary
e) write the formula for transformation ratio.
Q.2 (a) Describe briefly with the help of a well labeled diagram, the basic elements of AC generator
(b) State its underlying principle
(c) Show diagrammatically , how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the value for the instantaneous value of the emf in the coil.
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