Available Answers

1. 1.

   Write true or false for each statement. Rewrite the false statement correctly.

   1. To make an electromagnet, a coil of insulated copper wire is wound over a soft iron rod.
   2. In a U-shaped electromagnet, north pole and south pole cannot be obtained.
   3. An electromagnet cannot be used to separate iron from the mixture or copper, iron and on stainless steel.
   4. Electric bell is the most common example in which magnetic effect of current is used.
   5. Charge at rest has a magnetic field developed around it.
   6. The end of a current carrying coil. which has current in the clockwise direction, acts as north pole.
   7. When a closed coil and a magnet move together in such a way that the distance between them does not change, then no current will be induced in the coil.
   8. In an electric motor. a closed coil is rotated speedily in a magnetic field to get current.
   9. In a transformer. the primary coil converts electrical energy into magnetic energy and the secondary coil converts magnetic energy into electrical energy.
2. 2.

   Fill in the blanks :

   1. On passing electric current through a wire, _______________ field is developed around it.
   2. The direction of magnetic field developed around a current carrying conductor depends on _______________, whereas its strength depends on _______________ of current.
   3. A freely suspended current carrying coil behaves like a _______________ _______________ and always rests in _______________ direction.
   4. A transformer works on the principle of _______________.
   5. The direction of magnetic field developed around a straight current carrying conductor can be obtained by _______________ rule.
   6. The right hand screw rule is used to find _______________.
   7. _______________ converts electrical energy into mechanical energy.
   8. _______________ transformer will be used to get 180V from a 230V supply.
3. 3.

   Tick the most appropriate answer:

   (a) Around a current carrying conductor, there is:

   1. a magnetic field
   2. an electric field
   3. both magnetic field and electric field
   4. no magnetic field

   (b) The end of a current carrying coil at which the current is in anticlockwise direction, behaves as :

   1. north-pole
   2. south-pole
   3. neutral point
   4. none of the above

   (c) If one end of a current carrying coil behaves as south pole, the current in the coil is in:

   1. anticlockwise direction
   2. clockwise direction
   3. straight line
   4. direction cannot be found

   (d) An electric motor converts .

   1. potential energy into kinetic energy
   2. kinetic energy into electrical energy
   3. electrical energy into mechanical energy
   4. potential energy into mechanical energy.

   (e) A dynamo works on the principle of :

   1. magnetic effect of current
   2. electromagnetic induction
   3. force on a current carrying conductor placed in a magnetic field
   4. none of the above

   (f) The primary coil of a transformer :

   1. is connected to an A.C. source
   2. connected to a D.C. source
   3. converts A.C. into D.C.
   4. none of the above

   (g) If the number of turns in the primary coil of a transformer is more than the number of turns in its secondary coil, then the transformer gives out :

   1. higher voltage
   2. lower voltage
   3. same voltage
   4. none of the above

   (h) In order to coven 160 volt into 220 volt. we use :

   1. step-down transformer
   2. a dynamo
   3. an electric motor
   4. step-up transformer
4. 4.

   Write a short note on 'electromagnet'.

5. 5.

   Write a short note on 'electric motor'.

6. 6.

   Write a short note on 'dynamo'.