K.C.S.E Physics Q & A - MODEL 2015PP2QN15

K.C.S.E Physics Q & A - MODEL 2015PP2QN15

​.(a) State two factors that determine the resistance of a metallic conductor. 
(b) Explain how a fuse safeguards electrical appliances against excessive currents. 

​(c) A hair dryer is rated 2.5 kW, 240 V.
(i) Determine whether a 10 A fuse may be suitable for the hair dryer.
(ii) Determine the cost of using the hair dryer for 3 hours if the cost of electricity is Ksh 0.80 per kilowatt hour.

answer

​(a) length of conductor
area of cross-section
temperature
resistivity of conductor
(b) When excessive currents flow through the circuit, the wire gets heated and melts hence
breaking the circuit.

​Fuse not suitable since current through the appliance is higher than the fuse rating