i) Draw a simple labelled diagram of a d.c. electric motor?
ii) What is the function of the split rings in a D.C motor?
iii) State one advantage of a.c. over d.c.?i)
The labelled diagram of a d.c. electric motor is as shown below:
ii)
When the coil rotates, the split parts of ring rotate with it to flow the current in armature coil in such a way that it always keep on rotating in the same manner.
iii)
D.C. can be stored in battery but A.C. cannot.
i) Name the high energetic invisible electromagnetic waves which help in the study of the structure of crystals.
ii) State an additional use of the waves mentioned in part (e) (i)?i) X-rays.
ii) X-rays are used for detection of fracture in bones, teeth etc.
On reversing the direction of the current in a wire, the magnetic field produced by it gets .....
reversed
i) How does the heat produced in a wire or a conductor depend upon the:
1. current passing through the conductor.
2. Resistance of the conductor?
ii) Draw a simple sketch of the step-down transformer. Label the different parts I the diagram.
i)
1. Heat produced in a wire is directly proportional to the square of current through the conductor. (H 
I2)
2. Heat produced in a conductor is inversely proportional to the resistance of the wire.
ii)
The step down transformer is as follows:
Switch
