K.C.S.E Physics Q & A - MODEL 2014PP2QN14

K.C.S.E Physics Q & A - MODEL 2014PP2QN14

​(a) Figure 6 shows a simple electric bell circuit

​(i) Name the parts labelled:
(I) D 
(II) E 
(ii) When the switch is closed, the hammer hits the gong repeatedly. Explain why:
(I) the hammer hits the gong. 
(II) the hammer hits the gong repeatedly. 
(b) An electric bulb is rated 60 W, 240 V. Determine:
(i) the current that flows through it when it is connected to a 240 V supply.
(ii) the resistance ol the bulb. 

answers

​(a) (i) I D - soft iron armature 
II E contacts 
(ii) I. Soft iron core is magnetized  and attracts the armature the hammer hits 
the gong.
II. Contact is broken  when armature is  attracted by the core. The core then loses magnetism. 
The armature loses magnetism and  springs back making contact again and the process is repeated.