Question 1
(a) (i) Define conductor.
(ii) State three properties of a conductor.
(b) An electric pressing iron takes 5 A when operated on a 220 V supply. Calculate the cost of operating the pressing iron for 12 hours at 20 kobo per kilowatt-hour (kWh).
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The expected responses were:
- (i) Definition of Conductor
Conductors are materials which offer low resistance to the flow of current.
(ii) Properties of a conductor
- High thermal conductivity
- Low electrical resistance
- Mechanically strong and flexible
- High resistance to corrosion
- Allows free movement of electrons or charges
- Zero charge density in the conductor
(b) Given that Current I = 5 A
V = 220 V
t = 12 hours
Power = IV
= 5 × 220 = 1100 W = 1.1 kW
Energy Consumed = Power × Time
= 1.1 kW × 12 hrs
= 13.2 kWh
Cost of operation of 20 kobo per kWh
= 13.2 x 20
= 264 Kobo
= ₦ 2.64
Many of those who attempted this question stated the definition and the three properties correctly and got the values required from calculation correctly. However, many did not put the unit.