State two factors that determine the resistance of metallic conductor and explain how a fuse safeguards electrical appliances against excessive currents.

      

a) State two factors that determine the resistance of metallic conductor.
b) Explain how a fuse safeguards electrical appliances against excessive currents.
c) A hair dryer is rated 2.5kW, 240 V.
i) Determine whether a 10 A fuse may be suitable for the hair dryer
ii) Determine the cost of using the dryer for 3 hours if the cost of electricity is Ksh. 0.80 per kilowatt hour.

  

Answers


John
a) i) The length of the conductor

ii) The thickness/diameter/area of cross section of the conductor

iii) Type of metal conductor

b) It has a thin short piece of wire which overheats and melts if a current greater than its rating flows through it hence breaking the circuit that it connects

c) i) I = $\frac{P}{V}$ = $\frac{2500W}{240V}$ = 10.41 A

Fuse is not suitable because it exceeds the fuse rating.

ii) No of kWh = 2.5 x 3 = 7.5 kWh

Cost = 7.5 x 0.8 = Kshs 6.0

johnmulu answered the question on February 20, 2017 at 05:49


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