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Subelement I
Power Sources
Section 60
Batteries-1
When a lead-acid storage battery is being charged, a harmful effect to humans is:
  • Internal plate sulfation may occur under constant charging.
  • Emission of oxygen.
  • Emission of chlorine gas.
  • Correct Answer
    Emission of hydrogen gas.
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A battery with a terminal voltage of 12.5 volts is to be trickle-charged at a 0.5 A rate. What resistance should be connected in series with the battery to charge it from a 110-V DC line?
  • 95 ohms.
  • 300 ohms.
  • Correct Answer
    195 ohms.
  • None of these.

(110V - 12.5V) / 0.5A = 195 ohms

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What capacity in amperes does a storage battery need to be in order to operate a 50 watt transmitter for 6 hours? Assume a continuous transmitter load of 70% of the key-locked demand of 40 A, and an emergency light load of 1.5 A.
  • 100 ampere-hours.
  • Correct Answer
    177 ampere-hours.
  • 249 ampere-hours.
  • None of these.

\[40A \times 70\% = 28A\]

\[28A + 1.5A = 29.5A\]

\[29.5 A \times 6 \text{ Hours} = 177 \text{ ampere-hour}s\]

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What is the total voltage when 12 Nickel-Cadmium batteries are connected in series?
  • 12 volts.
  • 12.6 volts.
  • Correct Answer
    15 volts.
  • 72 volts.

The voltage of a single Nickel-Cadium battery is about 1.2 volts. When batteries are in series you add the voltage for each cell together (using multiplication since they are all the same) to find the total voltage.

\(1.2V \times 12 = 14.4V\) or about \(15\) volts.

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The average fully-charged voltage of a lead-acid storage cell is:
  • 1 volt.
  • 1.2 volts.
  • 1.56 volts.
  • Correct Answer
    2.06 volts.

If you're old enough to remember car batteries before they were maintenance free, you'll remember popping off the covers to expose 6 holes to which you would add water. So, each battery contains 6 cells. You can still see this in some high-end car batteries like Optima sells. Instead of the flat-sided box, the battery looks more like a 6-pack.

Car batteries hold a little over \(12\) volts, so the math is easy: \[\frac{12.37 V}{6\text{ cells}} = 2.06\text{ volts per cell}\]

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A nickel-cadmium cell has an operating voltage of about:
  • Correct Answer
    1.25 volts.
  • 1.4 volts.
  • 1.5 volts.
  • 2.1 volts.
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