{"id":30070,"date":"2018-07-28T08:45:42","date_gmt":"2018-07-28T08:45:42","guid":{"rendered":"https:\/\/cbselibrary.com\/?p=30070"},"modified":"2022-03-28T18:50:53","modified_gmt":"2022-03-28T13:20:53","slug":"a-new-approach-to-icse-physics-part-2-class-10-solutions-electromagnetism","status":"publish","type":"post","link":"https:\/\/cbselibrary.com\/a-new-approach-to-icse-physics-part-2-class-10-solutions-electromagnetism\/","title":{"rendered":"A New Approach to ICSE Physics Part 2 Class 10 Solutions Electromagnetism"},"content":{"rendered":"

A New Approach to ICSE Physics Part 2 Class 10 Solutions Electromagnetism.<\/span><\/h2>\n

These Solutions are part of A New Approach to ICSE Physics Part 2 Class 10 Solutions.<\/a> Here we have given A New Approach to ICSE Physics Part 2 Class 10 Solutions Electromagnetism.<\/p>\n

Exercise – 1<\/strong><\/span><\/p>\n

Question 1.<\/span><\/strong>
\nWhen can an electric charge give rise to a magnetic field?
\nAnswer:<\/strong><\/span>
\nWhen electric charge is in motion e. charge flows, it gives rise to magnetic field.<\/p>\n

Question 2.<\/span><\/strong>
\nDescribe Oersted\u2019s experiment to show that a conductor carrying current produces a magnetic field around it
\nAnswer:<\/strong><\/span>
\nOersted\u2019s Experiment :
\n<\/strong>Set up the apparatus as shown in fig. when switch is in open circuit
\n\"A
\n<\/span><\/span>magnetic needle points in north direction. Showing there is no magnetic field around it. Now when switch is closed and current flows through the wire, the magnetic needle gets deflected from north. This shows that conductor carrying current produces magnetic field around it and deflects the magnetic needle.<\/p>\n

Question 3.<\/span><\/strong>
\n(a) How will you plot the magnetic field lines around a straight conductor carrying current ?
\n(b) State two rules by which you can determine the direction of the magnetic field around a straight conductor.
\nAnswer:<\/strong><\/span>
\n(a)<\/strong> To plot the magnetic field lines around a straight conductor carrying current: Pass straight conductor through a cardboard or glass-plate. And pass current.
\n\"A
\nFrom A to B direction in the upward direction. Sprinkle iron filings on glass plate. Tap the glass plate, the iron filing will arrange themselves in circles around the conductor along the magnetic lines of force. The magnetic fields are circular in nature. The direction of magnetic field can be detected with the help of magnetic compass and direction is found anti clock wise.<\/p>\n

(b) Two rules are :<\/strong><\/p>\n

Right hand thumb rule:<\/strong> \u201cImagine you are holding the current carrying wire in your right-hand so that your thumb points in the direction of current, then the direction in which your fingers encircle the wire will give the direction of magnetic field lines around the wire.\u201d<\/p>\n

\"A
\nMax Well\u2019s Screw Rule :<\/strong> \u201cImagine driving a cork screw in the direction of current, then the direction in which we turn its handle is the direction of magnetic field (or magnetic field lines).<\/p>\n

\"A<\/p>\n

Question 4.<\/span><\/strong>
\n(a) Draw a set up for plotting magnetic field around a circular coil carrying current.
\n(b) State the properties of the magnetic field in 4(a).
\nAnswer:
\n<\/strong><\/span>(a)<\/strong>
\n\"A
\n(b) Properties of the magnetic field :<\/strong><\/p>\n

    \n
  1. The magnetic field lines are circular near current carrying loop.<\/li>\n
  2. At the center of the circular loop the magnetic field lines are in the same direction and strength of magnetic field increases.<\/li>\n<\/ol>\n

    Question 5.<\/span><\/strong>
    \nWhat is a solenoid ? Draw a magnetic field around a solenoid, when direct current flows through it. How will you find the magnetic polarity of a solenoid without using a magnetic needle ?
    \nAnswer:<\/strong><\/span>
    \nSolenoid :<\/strong> \u201cIs a long coil containing a large number of close turns of insulated copper wire.\u201d
    \n\"A
    \nMagnetic polarity of solenoid can be determined like a bar magnet i.e. when it is suspended freely, it will come to rest pointing in North and South direction or polarity can be checked by bringing north pole of a bar magnet. The pole repelled by north pole must be North pole of solenoid.<\/p>\n

    Question 6.<\/span><\/strong>
    \nHow does the magnetic field set up in a solenoid changes when:
    \n<\/strong>(a) number of turns are increased ?
    \n(b) diameter of the solenoid is increased ?
    \n(c) strength of the current is increased ?
    \n(d) a soft iron core is placed in it ?<\/p>\n

    Answer:<\/strong><\/span><\/p>\n

    (a)<\/strong> When number of turns are increased magnetic field will be stronger.
    \n(b)<\/strong> When diameter of the solenoid is increased but diameter should be less than the length of solenoid, so that parallel lines should add up to give a stronger field.
    \n(c)<\/strong> When strength of current is increased stronger will be the magnetic field produced.
    \n(d)<\/strong> When soft iron core is placed in the solenoid very strong magnetic field is produces.<\/p>\n

    Question 7.<\/span><\/strong>
    \nGive four differences between an electromagnet and a permanent magnet.
    \nAnswer:<\/strong><\/span>
    \nDifferences between electromagnet and permanent magnet:
    \n<\/strong>Electromagnet:<\/strong><\/p>\n

      \n
    1. It is temporary magnet<\/li>\n
    2. It strength can be changed, by changing the current.<\/li>\n
    3. Polarity can be changed by changing the direction of current.<\/li>\n
    4. Produces very strong magnetic force.<\/li>\n<\/ol>\n

      Permanent Magnet<\/strong><\/p>\n

        \n
      1. It is permanent magnet.<\/li>\n
      2. It strength cannot be changed.<\/li>\n
      3. Polarity cannot be changed.<\/li>\n
      4. Produces weak magnetic force.<\/li>\n<\/ol>\n

        Question 8.<\/span><\/strong>
        \nState four practical applications of electromagnets.
        \nAnswer:<\/strong><\/span>
        \nFour applications of electromagnet :<\/strong><\/p>\n

          \n
        1. In electric bell.<\/li>\n
        2. In magnetising steel bars.<\/li>\n
        3. For scanning machines (MRI)<\/li>\n
        4. In electric motor, generator.<\/li>\n<\/ol>\n

          Question 9.<\/span><\/strong>
          \n(a) On what factors does the force experienced by a straight conductor placed in a magnetic field depend
          \n(b) State the law which determines the force experienced by a conductor.
          \nAnswer:<\/strong><\/span>
          \n(a) Factors on which force experienced by a straight conductor depend :<\/strong><\/p>\n

            \n
          1. Current passing :<\/strong> direct proportional to current passing.<\/li>\n
          2. Inversely proportional to the distance of that point from the wire.<\/li>\n<\/ol>\n

            (b)<\/strong> When a conductor carrying current is placed in a magnetic field in a direction other them the direction of magnetic field, experiences a force called Lorentz force. This force is perpendicular to both, the direction of current I and the direction of magnetic fields B.
            \nThis law is called :
            \nFleming\u2019s left hand rule :<\/strong> \u201cStretch the fore finger, control finger and the thumb of your left hand mutually perpendicular to each other. If the fore-finger points in the direction of magnetic field, central finger indicates the direction of current, then the thumb will indicate the direction of motion of conductor (i.e., force on conductor)<\/p>\n

            Question 10.<\/span><\/strong>
            \n(a) Draw a neat and labelled diagram of a d.c. motor and explain its construction and working.
            \n(b) How can you make a d.c. motor more powerful ?
            \n(c) How can you convert its jerky motion into uniform circular motion ?
            \nAnswer:<\/strong><\/span>
            \n(a)<\/strong> D.C. Motor
            \n\"A<\/p>\n

            Construction :<\/strong> A d.c. motor consists of :<\/p>\n

              \n
            1. Rectangular coil ABCD of insulated copper wire moved between two Horse shoe<\/li>\n
            2. Permanent magnet M such that AB and CD are perpendicular to the magnetic field.<\/li>\n
            3. Two half rings (commutators) of copper X, Y are soldered to ends A and D of coil to change the direction of current flowing after every half rotation of the coil.<\/li>\n
            4. Two carbon brushes P and Q fixed to the base of motor keep pressing highly against commutators. Battery to supply the current to coil is connected to the coil. The function of brushes is to make contact with the rotating rings of\u00a0 the commutator and through them to supply current to the coil.<\/li>\n<\/ol>\n

              Multiple Choose Questions<\/strong><\/span><\/p>\n

              Tick (\u2713) the most appropriate option.<\/strong><\/p>\n

              1.\u00a0A wire carrying a current is held over a freely suspended magnetic needle, such that the current in the wire flows from south to north. The direction in which the north end of freely suspended magnetic needle will point towards.<\/strong>
              \n(a) West
              \n(b) East<\/strong>
              \n(c)South
              \n(d) North<\/p>\n

              2. In an electric motor :
              \n<\/strong>(a) mechanical energy changes to heat energy
              \n(b) mechanical energy changes to electric energy
              \n(c) electric energy changes to mechanical energy<\/strong>.
              \n(d) electric energy changes to magnetic energy<\/p>\n

              3. By reversing the direction of current in an electromagnet, the magnetic field produced by it
              \n<\/strong>(a) increases in strength
              \n(b) remains unchanged in strength and direction
              \n(c) gets reversed in direction<\/strong>
              \n(d) decreases in strength<\/p>\n

              4. The power of a d.c. motor can be increased :
              \n<\/strong>(a) by increasing number of turns in its coil
              \n(b) by laminating its soft iron core
              \n(c) by increasing the strength of current flowing through it
              \n(d) all of these<\/strong><\/p>\n

              5. Commutator is a device in a d.c. motor which :
              \n(a) increases the power
              \n(b) reverses direction of current coil after full rotation of coil
              \n(c) reverses direction of current after half rotation of coil<\/strong>
              \n(d) increases the strength of electromagnet<\/p>\n

              6. Which is not the use of an electromagnet ?
              \n<\/strong>(a) Used in electric appliances such as electric bell and electric fans.
              \n(b) Used for magnetising steel bars.
              \n(c) Used for making sensitive magnetic compass.<\/strong>
              \n(d) Used in separating iron particles from a scrap of iron and other metals.<\/p>\n

              7. Which is not the property of a solenoid ? The magnetic field of solenoid can be increased
              \n<\/strong>(a) by increasing the number of turns in the solenoid.
              \n(b) by increasing the strength of current flowing through the solenoid.
              \n(c) by placing a stainless steel core within the solenoid.<\/strong>
              \n(d) by placing a laminated soft iron core within the solenoid.<\/p>\n

              Exercise – 2<\/strong><\/span><\/p>\n

              Question 1.<\/span><\/strong>
              \nState Faraday\u2019s laws of electromagnetic induction.
              \nAnswer:<\/strong><\/span>
              \nFaraday\u2019s Laws of Electromagnetic Induction :<\/strong><\/p>\n

                \n
              1. \u00a0When ever there is a change in the magnetic flux linked with a coil an e.m.f. is induced. The induced e.m.f. lasts as long as the change lasts (i-e-, there is a change in the magnetic flux linked with the coil.<\/li>\n
              2. The magnitude of the e.m.f. induced is directly proportional to the rate of change of the magnetic flux linked with the coil. If the magnetic flux changed at a fixed rate, a stready e.m.f. is produced.<\/li>\n<\/ol>\n

                Question 2.<\/span><\/strong>
                \nState
                \n(a) Fleming\u2019s right hand rule,
                \n(b) Lenz\u2019s law for finding the direction of induced current. Which of the above laws is most suitable for finding the direction of current in<\/p>\n

                  \n
                1. straight conductor<\/li>\n
                2. \u00a0coiled conductor ?<\/li>\n<\/ol>\n

                  Answer:<\/strong><\/span>
                  \n(a) Fleming\u2019s right hand rule:<\/strong><\/p>\n

                  Or<\/strong><\/p>\n

                  (1) Generator rule :<\/strong> \u201cStretch the thumb, fore finger and central finger of right hand mutually perpendicular to each other. If the fore finger indicates the direction of magnetic field and thumb indicates the direction of motion of the conductor then central finger will indicate the direction of induced current.\u201d
                  \n\"A
                  \n(2) Lenz\u2019s Law : <\/strong>\u201cThe direction of induced e.m.f. (or induced current) always tends to oppose the cause which produces it.\u201d<\/p>\n

                  (a)<\/strong> In straight conductor \u2014 Fleming\u2019s Right Hand Rule
                  \n(b)<\/strong> in coiled conductor \u2014 Lenz\u2019s Law.<\/p>\n

                  Question 3.<\/span><\/strong>
                  \nWhat do you understand by the term mutual induction ? Describe an experiment in support of your answer.
                  \nAnswer:<\/strong><\/span>
                  \nMutual induction:<\/strong> \u201cThe phenomenon of production of induced e.m.f. in a closed coil, by varying the magnetic flux in another coil is called mutual induction.\u201d
                  \nExperiment :
                  \n\"A
                  \n<\/em><\/strong>P(primary coil) behaves as electro magnet when current passed by opening and closing the switch and pointer of the secondary coil (s) shows deflection proving that induced e.m.f. is produce in secondary coil. As soon as the switch is off (open circuit) deflection stops in secondary coil.
                  \nOr
                  \nThe induced e.m.f. can be generated in the secondary coil, by placing the primary coil permanently in the secondary coil, and rapidly closing and opening the switch closing switch amounts to increases in magnetic flux in the primary coil, and hence in the secondary coil. Opening the switch amounts to decrease in magnetic flux in the primary and the secondary coil. Thus induced e.m.f. is generated in secondary coil.<\/p>\n

                  Question 4.<\/span><\/strong>
                  \nWhat do you understand by the terms (a) self induction (b) eddy current ?
                  \nAnswer:<\/strong><\/span>
                  \n(a) Self induction:<\/strong> \u201cThe phenomenon due to which a current flowing through a part of coil, induces an e.m.f. in the rest of coil due to change in magnetic flux is called self induction.\u201d<\/p>\n

                  (b) Eddy currents :<\/strong> \u201cThe current produced in any metallic conductor when a magnetic flux is changed around it is called Eddy Current.<\/p>\n

                  Question 5.<\/span><\/strong>
                  \n(a) Describe with the help of a clear diagram the structure of a.c. transformer, suitable for lighting 12 V lamp from 240 V mains.
                  \n(b) Explain how a transformer reduces emf ?
                  \n(c) Why are transformers so important for the transmission of energy ?
                  \nAnswer:<\/strong><\/span>
                  \n(a)<\/strong> We are to transformer for lighting 12V lamp from 240 V mains.
                  \nTherefore step down transformer is needed.
                  \nThe magnitude of induced e.m.f. is produced by the formula.
                  \n\"A
                  \nPrimary coil:
                  \n<\/strong><\/p>\n