K.C.S.E Physics Q & A - MODEL 2011PP2QN17

K.C.S.E Physics Q & A - MODEL 2011PP2QN17

​(a) State what is meant by the term “electromagnetic induction”. 
(b) Figure 9, shows a simple electric generator

​(i) Name the parts labelled P and Q. 
P .
Q
(ii) Sketch on the axes provided, a graph to show how the magnitude of the potential difference across R, changes with the time t. 

​(iii) State two ways in which the potential difference produced by such a generator can be increased.
(c) In a transformer, the ratio of primary turns to the secondary turns is 1:10. A current of 500mA flows through a 200 ohms resistor in the secondary circuit.
Assuming that the transformer is 100% efficient, determine:
(i) the secondary voltage;
(ii) the primary voltage; 
(iii) the primary current.

answers

​(a) The production of induced e.m.f when the magnetic flux linking a circuit is changed;
(b) (i) P - brushes
Q - slip rings

​(iii) Increasing number of turns/coils;
Increasing speed of rotation;
Increasing strength of field;
Winding the coil on soft iron core.