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Physics for Secondary Schools
batteries. Although it is rechargeable, the
2. Close the switch and adjust the accumulator does not last forever. After
rheostat so that the reading on the some time, the cells can no longer be
ammeter is 1.5 A. Let the current recharged. If well taken care of, however,
flow for about one minute. lead-acid batteries can last for a long
3. Open the switch and use the voltmeter time. The following are some guidelines
FOR ONLINE READING ONLY
to measure the potential difference on how to care for lead-acid batteries:
across the plates. 1. The cells should be charged
4. Connect a 2.5 V bulb across the regularly and should never be left
plates and observe its brightness. discharged. Cars have alternators that
5. Disconnect the circuit, pull out the automatically charge the batteries.
plates and note the colour of both 2. The acid level should be maintained
the positive and the negative plates. by adding distilled water when
necessary. Never add acid.
Questions 3. The terminals should be kept clean
and greased.
(a) What was the voltage across the
lead plates when a 1.5 A current was 4. Rough handling should be avoided,
allowed to flow for one minute? for example, dropping the battery
(b) What was the colour of each plate down.
at the end of an experiment? 5. The cells should not be short-circuited,
that is, they should not be allowed to
drive very large currents.
The plates produce a potential difference
of approximately 2.0 V or slightly more 6. When charging, the rate specified
after running a constant current for a by the manufacturer should not be
short time. For a short period of time, this exceeded.
voltage causes the bulb to glow brightly. Uses of cells and accumulators in daily
The plate that is linked to the positive life
terminal of a power source becomes the The following are some of the uses of
positive terminal of this cell. The cell is cells and lead-acid batteries:
being charged when the current passes
through the plates. The positive plate Dry cells are used for operating radios,
changes its colour to brownish red. This electronic calculators and other small
is due to lead dioxide (or red lead) which electrical devices. On the other hand,
is formed from lead during the charging accumulators offer a lot of use in our
daily life as follows:
process.
1. They are used to provide power to
motor vehicles. Figure 2.62 shows
Lead-acid accumulators are commonly a typical car battery.
used as car and photovoltaic system
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Physics Form 2 Final.indd 86 25/10/2025 10:26
