UNIT 14
Current Electricity
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After
studying this unit, students will be able to:
•
define electric current.
•
describe the concept of conventional current.
•
understand the potential difference across a circuit component and name
its unit .
•
describe Ohm’s law and its limitations.
•
define resistance and its unit(Ω).
•
calculate the equivalent resistance of a number
of resistances connected in series and also in parallel.
•
describe the factors affecting the resistance of a metallic conductor.
•
distinguish between conductors and insulators.
•
sketch and interpret
the V-I characteristics graph
for a metallic
conductor, a
filament lamp and a
thermister.
•
describe how energy is dissipated in resistance and explain Joule’s
law.
•
apply the equation E=I.Vt = I2 Rt = V2 t /R to solve numerical problem.
•
calculate the cost of energy when given the cost per kWh.
•
distinguish between D.C and A.C.
•
identify circuit components such as switches, resistors, batteries etc.
•
describe the use of electrical measuring devices
like galvanometer, ammeter, and voltmeter (construction and working principles
not required).
•
construct simple series (single path) and parallel circuits (multiple
paths).
•
predict the behavior of light bulbs in series
and parallel circuits such as for celebration lights.
•
state the functions of the live, neutral and earth wires in the
domestic main supply.
•
state reason why domestic supplies are connected in parallel.
•
describe the hazards of electricity (damage
insulation, overheating of cables, damp conditions).
•
explain the use of safety measures in household
electricity, (fuse, circuit breaker, earth wire).
