Practice Test

Q1) The magnetic field due to a current element is independent of Show Answer

Q2) The unit of a current element is Show Answer

Q3) The magnetic field (B) on the axis of a circular coil and a far away distance r from the centre of the coil are related as Show Answer

Q4) What happens to the magnetic field at the centre of a circular current carrying coil if we double the radius of the coil keeping the current unchanged ? Show Answer

Q5) When we double the radius of a coil keeping the current through it unchanged, what happens to the magnetic field, directed along its axis, as far off points ? Show Answer

Q6) The strength of the magnetic field around an infinite current carrying conductor is Show Answer

Q7) A current carrying power line carries current from west to east. Then the direction of the magnetic field 2 m above it is Show Answer

Q8) A metallic pipe carries a direct current. Which of the following statements is true about the existence of a magnetic field ? Show Answer

Q9) In an unmagnetised state, magnetic domains of a substance are oriented as Show Answer

Q10) A magnetic field exerts no force on a/an Show Answer

Q11) The magnetic field due to a current carrying toroidal solenoid does not depend on the Show Answer

Q12) What will be the magnetic field in the empty space enclosed by a toroidal solenoid of radius r ? Show Answer

Q13) What is the magnetic field in the space outside a toroidal solenoid of radius r ? Show Answer

Q14) The energy resides in a current carrying inductor in the form of Show Answer

Q15) " An electric current is always accompanied by a magnetic field" was discovered by Show Answer

Q16) Tesla (T) is the SI unit of Show Answer

Q17) Which of the following graphs correctly represents the variation of magnetic flux density (B) with distance (r) for a straight long wire carrying an electric current ? Show Answer

Q18) The magnetic field at a distance r from a long wire carrying I is 0.6 T. Then the magnetic field at a distance 2r is Show Answer

Q19) A current is passed through a straight wire. The magnetic field established around it has its lines of force Show Answer

Q20) The dimensions of pole strength are Show Answer

Q21) The dimensions of magnetic dipole moment are Show Answer

Q22) The magnetic field due to a long straight wire carrying current I is proportional to Show Answer

Q23) A wire of length L (metre) carrying a current I (ampere) is bent in the form of a circle. Its magnitude of magnetic moment will be Show Answer

Q24) When a charge particle moves in a magnetic field, its kinetic energy always Show Answer

Q25) Which of the following instruments is used to measure magnetic field ? Show Answer

Q26) When the N-pole of a magnet points towards the geographic north and the S-pole towards the geographic south, the null points are at the Show Answer

Q27) When the N-pole of a magnet points towards the geographic south and S-pole towards the geographic north, the null points are at the Show Answer

Q28) The magnetic permeability of vacuum (in SI units ) is Show Answer

Q29) Static charge is a source of Show Answer

Q30) A moving charge is a source of Show Answer

Q31) An endless solenoid in the form of a ring is called Show Answer

Q32) An electron beam is moving south to north just above a magnetic needle then the north pole of the magnetic needle will point towards Show Answer

Q33) The magnetic moment per unit volume is called Show Answer

Q34) Which of the following magnetic materials is repelled by an external field ? Show Answer

Q35) Which of the following units is different from the others ? Show Answer

Q36) 1 T equals Show Answer

Q37) A bar magnet of magnetic moment q is divided into two equal parts by cutting it parallel to its length. Then the pole strength of the pieces will be Show Answer

Q38) A bar magnet of magnetic moment p is divided into two equal parts by cutting it parallel to its length. Then the magnetic moment of the pieces will be Show Answer

Q39) The distance between two magnetic poles is doubled and the pole strength of each is halved. How will the force between them change ? Show Answer

Q40) To shield an instrument from an external magnetic field it may be placed in a cabinet made of Show Answer

Q41) When a magnet is heated, its strength Show Answer

Q42) Which of the following cannot be ferromagnetic ? Show Answer

Q43) A small piece of a substance gets repelled by a strong permanent magnet. The substance must necessarily be Show Answer

Q44) What is a non-magnetic substance ? Show Answer

Q45) The most suitable metal for making permanent magnet is Show Answer

Q46) The SI unit of magnetic dipole moment is Show Answer

Q47) Earth's magnetism was discovered by Show Answer

Q48) The relative peremeability of iron is of the order of Show Answer

Q49) To which category of magnetic substances do the ferrites belong ? Show Answer

Q50) A motor converts ___ energy into ___ energy. Show Answer

Q51) The direction of lines of force of the magnetic field produced by a straight wire carrying current can be obtained by using Show Answer

Q52) Electromagnetic induction is involved in Show Answer

Q53) Who constructed the first electric motor ? Show Answer

Q54) Most of the power stations in India produce Show Answer

Q55) The alternating current produced in India changes its direction every Show Answer

Q56) If the current flows always along the same direction, it is called Show Answer

Q57) Assertion :
Steel is not attracted by a magnet.
Reason :
Steel is not a magnetic substance. Show Answer

Q58) Assertion :
The pole of a magnet cannot be separated.
Reason :
The atoms themselves are magnets. Show Answer

Q59) Assertion :
The magnetic field of an atom is due to both, the orbital motion and spinning motion of every electron.
Reason :
A charged particle produces a magnetic field. Show Answer

Q60) Assertion :
When the radius of a circular wire carrying current is doubled, its magnetic moment becomes four times.
Reason :
Magnetic moment depends on the area of the loop. Show Answer

Q61) The graph between B and distance (r) from the axis of cylinder (radius R) for a current flowing through the cylinder is best shown by Show Answer

Q62) A rectangular piece of soft iron is kept in a uniform magnetic field. Which of the following correctly represents the lines of force in the region (see figure below) ? Show Answer

Q63) A freely suspended magnetic needle at the magnetic north pole of the earth Show Answer

Q64) Consider the following statements
The core of transformer is laminated, because it
(I) prevents leakage of flux
(II) gives more secondary voltage
(III) reduces eddy currents
Which of the statements is/are correct ? Show Answer

Q65) When a coil of wire is rotated in a uniform magnetic field, a/an Show Answer

Q66) In combined field of a magnet and earth two null points are located on its axis. The magnet is placed with its axis Show Answer

Q67) The soft iron (used as core material) has Show Answer

Q68) The value of intensity of horizontal component of certain magnetic field is approximately Show Answer

Q69) If a metal is weekly repelled by a magnet, then the metal is expected to be Show Answer

Q70) A current is flowing in a circular conductor in clockwise direction. The coil is in the plane of the paper. The direction of the magnetic, field is Show Answer

Q71) An electric motor is used to convert Show Answer

Q72) Frequency of the AC main in India is Show Answer

Q73) ASSERTION (A) :
An isolated stationary charge does not produce a magnetic field.
REASON (R) :
For producing a magnetic field, a magnetic material is essential.
Show Answer

Q74) Consider the following statements
As one moves from one place to another, the magnetic field of the earth will vary
(I) in magnitude
(II) in direction
(III) linearly with height
(IV) linearly with temperature of the place
Of the above statements Show Answer

Q75) Which of the following statements are not correct ?
(I) Magnetic monopoles do not exist.
(II) Two iron bars which are magnetised always attract.
(III) A wire freely suspended in a magnetised field orients itself parallel to the field.
(IV) Copper is diamagnetic and aluminium is paramagnetic.
Choose the answer from the following codes : Show Answer

Q76) Which of the following statements are correct regarding ferromagnetic materials ?
(I) They contain iron
(II) They exhibit hysteresis
(III) They are characterised by atoms with permanent dipole moments
Choose the answer from the codes given below : Show Answer

Q77) Which one of the following statements about electric or magnetic fields is not true ? Show Answer

Q78) Heating a magnet will Show Answer

Q79) In the process of magnetisation of a bar Show Answer

Q80) Two conducting parallel wires carry current in opposite directions. They will Show Answer

Q81) The direction of the induced emf during electromagnetic induction is determined by Show Answer

Q82) The electromagnetically induced current always flows in such a direction that the action of the magnetic field set-up by it tends to oppose the cause producing it. This is known as Show Answer

Q83) An emf of 5 V is produced by a self inductance when the current changes at a steady rate from 3 to 2 A in 1 ms. The value of self inductance is Show Answer

Q84) Two pure inductors, each of self inductance L, are connected in parallel but are well separated from each other, then the total inductance is Show Answer

Q85) The output of a dynamo using a split ring commutator is Show Answer

Q86) A conductor carrying current when placed in an external magnetic field, experiences a mechanical force. The device whose working is based on this principle is Show Answer

Q87) The function of compensating winding is to Show Answer

Q88) A choke coil Show Answer

Q89) A jet aeroplane has total wing span of 60 m and moving with a speed of 400 m/s. If the earth's magnetic field is 0.3 gauss, then the potential difference between the wing tips of a jet aeroplane is Show Answer

Q90) In a step-down transformer, the input voltage is 200 V and the output voltage is 5 V. The turn ratio of the transformer is Show Answer

Q91) A coil is wound on a frame of rectangular cross-section. If the linear dimensions of the frame are increased by a factor of 2 and the number of turns per unit length of the coil remain the same, the self inductance increases by a factor of Show Answer

Q92) A transformer has an efficiency of 80%. it works at 4 kW and 100 V. If the secondary voltage is 240 V, the current in the primary coils is Show Answer

Q93) The current passing through a choke coil of 5 H is decreasing at the rate of 2 A/s. The emf developed is Show Answer

Q94) A set-up transformer is used on a 120 V line to provide a potential difference of 2400 V at 2 A current. If the primary has 100 turns, then the number of turns in the secondary coil is Show Answer

Q95) Two electric bulbs, each designed to operate with a power of 500 W in 220 V lines are put in series in a 110 V. What will be the power generated by each bulb ? Show Answer

Q96) A silver and copper voltmeters are connected in parallel to 12 V battery of negligible resistance. In 30 min 1 g of Ag and 1.8 g of Cu are deposited. At what rate is energy being delivered by the battery ? Show Answer

Q97) A steady current of 5A maintained for 45 min deposits 4.572 g of Zn at the cathode. ECE of Zn is Show Answer

Q98) In a step-down transformer the input voltage is 22kV and the outer voltage is 550 V. The ratio of number of turns in the secondary to primary is Show Answer

Q99) A magnetic needle lying parallel to magnetic field requires W units of work to turn it through 60^o. The torque needed to maintain the needle in this position will be Show Answer

Q100) The temperature at and above which a ferromagnetic material become paramagnetic is called Show Answer

Q101) Points A and B are situated along the extended axis of 2 cm long have magnet at a distance x and 2x cm respectively from the pole nearer to the points. The ratio of magnetic fields at A and B will be Show Answer

Q102) The core used in transformers and other electromagnetic device is laminated to Show Answer

Q103) An artificial satellite with metal surface is moving around earth in a circular orbit. An induced current flows in the satellite. Which of the following statements is correct ? Show Answer

Q104) When power is draun from the secondary circuit of a transformer, the dynamic resistance Show Answer

Q105) A current carrying wire is known to produce magnetic lines of force around the conducting straight wire. The direction of the lines of force may be described by Show Answer

Q106) A positively charged particle projected towards west is deflected towards north by a magnetic field. The direction of the magnetic field is Show Answer

Q107) The earth's magnetic field is approximately Show Answer

Q108) In India, distribution of electricity for domestic purpose is done in the form of Show Answer

Q109) The polarity of an unmarked horse-shoe magnet can be determined by using Show Answer

Q110) Consider the following statements :
(I) If a piece of bar magnet is broken into two equally long pieces, the pieces will not lose the magnetic properties.
(II) Magnetic properties of a substance lie in the atomic level.
Which of the statement(s) given above is/are correct ? Show Answer

Q111) The torque on a rectangular coil placed in a uniform magnetic field is large when the Show Answer

Q112) The lines of force of a uniform magnetic field Show Answer

Q113) Magnets attract magnetic substances such as iron, nickel, cobalt, etc. They can also repel Show Answer

Q114) The direction of magnetic field at a point due to an infinity long wire carrying current is Show Answer

Q115) Magnetism of a bar magnet can be destroyed if it is
(I) kept in the magnetic meridian.
(II) placed in a direction opposite that of the earth's horizontal intensity
(III) heated to a temperature known as Curie temperature.
Select the correct answer using the code given below Show Answer

Q116) The magnetic lines of force due to the bar magnet Show Answer