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Science, , (Chapter 13)(Magnetic Effects of Electric Current), Class - 10, , , , , , Exercises, , , , , , Question 1:, Which of the following correctly describes the magnetic field near a long straight, wire?, (a) The field consists of straight lines perpendicular to the wire., (b) The field consists of straight lines parallel to the wire., (c) The field consists of radial lines originating from the wire., (d) The field consists of concentric circles centred on the wire., Answer 1:, (d) The field consists of concentric circles centred on the wire., On applying right-hand thumb rule, we find the direction of magnetic field. The, field is in the form of concentric circles centred on the wire carrying current., , Hence, the option (d) is correct., , Question 2:, The phenomenon of electromagnetic induction is, (a) the process of charging a body., (b) the process of generating magnetic field due to a current passing through a, coil., (c) producing induced current in a coil due to relative motion between a magnet, and the coil., (d) the process of rotating a coil of an electric motor., , Answer 2:, (c) producing induced current in a coil due to relative motion between a magnet, and the coil., In electromagnetic induction phenomenon an induced current begins to flow ina, coil whenever there is change in magnetic field in and around a coil., , Hence, the option (c) is correct.
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Question 3:, The device used for producing electric current is called a, (a) generator., (b) galvanometer., (c) ammeter., (d) motor, Answer 3:, (a) generator., An A.C. generator is the device used for producing an electric current., , Hence, the option (a) is correct., , Question 4:, The essential difference between an AC generator and a DC generator is that, (a) AC generator has an electromagnet while a DC generator has permanent, magnet., (b) DC generator will generate a higher voltage., (c) AC generator will generate a higher voltage., (d) AC generator has slip rings while the DC generator has a commutator, (This question is out of syllabus now), Answer 4:, (d) AC generator has slip rings while the DC generator has a commutator, , Question 5:, At the time of short circuit, the current in the circuit, (a) reduces substantially., (b) does not change., (c) increases heavily., (d) vary continuously., Answer 5:, (c) increases heavily., At the time of short circuiting the live wire and the neutral wire come into direct, contact. As a result, the current in the circuit abruptly increases., , Hence, the option (c) is correct.
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Question 6:, , State whether the following statements are true or false., , (a) An electric motor converts mechanical energy into electrical energy., , (b) An electric generator works on the principle of electromagnetic induction., , (c) The field at the centre of a long circular coil carrying current will be parallel, , straight lines., , (d) A wire with a green insulation is usually the live wire of an electric supply., Answer 6:, , (a) An electric motor converts mechanical energy into electrical energy. (False), , (b) An electric generator works on the principle of electromagnetic induction., , (True), , (c) The field at the centre of a long circular coil carrying current will be parallel, , straight lines. (True), , (d) A wire with a green insulation is usually the live wire of an electric supply., (False), , Question 7:, List three sources of magnetic fields., Answer 7:, Three methods of producing magnetic field are as follows:, > Magnetic field can be produced by placing a permanent bar magnet or a, horse-shoe magnet at the place, where magnetic field is required., > Magnetic field is produced around a current-carrying straight conductor or, a current carrying circular coil., > A very good method to produce magnetic field is due to flow of current in, a solenoid., , Question 8:, How does a solenoid behave like a magnet? Can you determine the north and, south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
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Answer 8:, When current is passed through a solenoid coil, magnetic field produced due to, each turn of solenoid coil is in the same direction. As a result, the resultant, magnetic field become very strong and uniform. The field lines inside the, solenoid are in the form of parallel straight lines along the axis of solenoid. Thus,, the solenoid behaves like a bar magnet. One end of solenoid behaves as a, magnetic North pole while the other end behaves as the South Pole., , , , We can determine the magnetic poles formed in a solenoid. The end of the, current-carrying solenoid, which attracts North Pole but repels South Pole of a, bar magnet, is behaving as south magnetic pole. The other end, which attracts, South Pole of a bar magnet but repels the North Pole, is behaving as north, magnetic pole. It is because like poles repel but unlike poles attract each other., , Question 9:, When is the force experienced by a current-carrying conductor placed in a, magnetic field largest?, , Answer 9:, The force experienced by a current-carrying conductor placed in a magnetic field, is largest when the current-carrying conductor is placed in a direction, perpendicular to that of magnetic field., , Question 10:, , Imagine that you are sitting in a chamber with your back to one wall. An electron, beam, moving horizontally from back wall towards the front wall, is deflected by, a strong magnetic field to your right side. What is the direction of magnetic field?
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Answer 10:, An electron beam moving horizontally from back wall towards the front wail is, , equivalent to a current flowing in the opposite direction (i.e., from front wall, towards the back wall). The deflection of electron beam as seen by observer is to, his right side and is shown in Figure. On applying Fleming's left-hand rule we, find that the magnetic field is acting in vertically downward direction., , Back wall|, | Front wall, , | Ongina’, , em a a ee direction of —_—, 1 os electron beam, |, , | e, RR,, , , , Question 11:, Draw a labelled diagram of an electric motor. Explain its principle and working., What is the function of a split ring in an electric motor?, , Answer II:, , Split rings, (P and Q), , , , , , , , , , , , K, 4HHHHH-—{+), A simple electric motor
