Question 1
(a) State one function of:
- a battery in the operation of a motor vehicle;
- an electrolyte in a battery.
(b) (i) State two factors that affect the capacity of a lead acid battery.
(ii) A lead acid battery delivers a current of 0.5 A steadily for 120 hours. Calculate the
capacity of the battery.
(c) Table 1 contains some components of a lead acid battery. Complete it by giving one
material used in making each of the parts listed.
Table 1
S/N |
Component part |
Material used |
(i) |
Positive plate |
|
(ii) |
Negative plate |
|
(iii) |
Separator |
|
(iv) |
Casing |
|
(v) |
Cell connectors |
|
Complete Table 1 by stating one symptom of fault and one remedy for each fault listed.
The expected responses were:
- (i) Function of a battery in the operation of a motor vehicle
- to supply the necessary current to the starter motor and ignition system while
cranking to start the engine
- to supply additional current when the demand is higher that the alternator can supply
- acts as electrical reservoir for current supply when necessary
(ii) Function of an electrolyte in a battery
- break down to cause the movement of ions which results in the flow of current.
- Serves as catalyst to make the battery conductive by promoting the movement of ions from the cathode to the anode and is reserve on discharge
- Stores chemical energy to be converted into electrical energy.
- (i) Factors that affect the capacity of a lead acid battery
- surface area of electrode
- plate surface area
- number of plates
- strength of electrode
- operating temperature
- age of battery
- rate of discharge
(ii) Calculation
capacity = current x time
= 0.5 x 120
= 60 Ah
- Table 1
S/N |
Component parts |
Material used |
(i) |
Positive plate |
lead oxide |
(ii) |
Negative plate |
Spongy lead |
(iii) |
Separator |
treated wood/plastic/hard rubber |
(iv) |
Casting |
ebonite/plastic/hard rubber |
(v) |
Cell connectors |
lead |
Question 1 required candidates to show understanding of basic terminology of the battery and total output of a battery. More so, other part of the question required candidates to show familiarity with the component parts of a lead acid battery. The Chief Examiner reported that majority of the candidates that attempted question 1 could neither show understanding of the materials component parts of batteries are made of nor state the factors that affect the capacity of a lead acid battery.