MODULE 3 CHAPTER5 QUIZ 1

05.DC Sources of Electricity ..................................

Question Number. 1. A 20 cell battery with each cell having an internal resistance of 0.1 ohms is charged with 2 leads having a total resistance of 0.1 ohms.

The battery is charged with a current of 5 amps. What is the charging voltage ?.

Option A. 0.5 volts.

Option B. 10.5 volts.

Option C. 0.005 volts.

Correct Answer is. 10.5 volts.

Explanation. Total battery internal resistance = 0.1 * 20 = 2 ohms, Total circuit resistance, including leads = 2 + 0.1 = 2.1 ohms, V = I * R = 5A * 2.1 ohms = 10.5V ..................................

Question Number. 2. Two 10V, 20 Ah batteries are connected in parallel and connected across a 10 ohm load. How long could they supply normal current before the voltage begins to decay?.

Option A. 40 hours.

Option B. 20 hours.

Option C. 4 hours.

Correct Answer is. 40 hours.

Explanation. Use Ohms law to work out the current (1A). Two batteries in parallel then rating is doubled (40 Ah) ..................................

Question Number. 3. A battery rated at 40 Ah will supply 200 mA for.

Option A. 200 hours.



Option B. 20 hours.

Option C. 5 hours.



Correct Answer is. 200 hours.

Explanation. 200 mA = 0.2 A. 40 Ah / 0.2 A = 200 hours ..................................

Question Number. 4. A zinc-carbon battery life depends upon. ...

Option A. the amount of zinc.

Option B. the purity of the carbon rod.

Option C. the amount of the electrolyte paste.

Correct Answer is. the amount of zinc.

Explanation. The zinc is slowly eaten away in a zinc carbon battery (primary cell) ..................................

Question Number. 5. When checking the SG of the electrolyte in a lead acid battery, you should.

Option A. check any cell because they will all be the same.

Option B. check only the no. 1 cell because it is the master cell.

Option C. check all cells because they may be different.

Correct Answer is. check all cells because they may be different.

Explanation. NIL ..................................

Question Number. 6. The PD at the terminals of an open circuit battery with a small internal resistance will be.

Option A. more than the EMF.

Option B. less than the EMF.

Option C. the same as the EMF.

Correct Answer is. the same as the EMF

. Explanation. EMF is the battery voltage (i.e. that which is written on the side of it) and the PD is the actual terminal voltage. If it is open circuit, no current flows to drop a voltage across the internal resistance so they are the same ..................................

Question Number. 7. An accumulation of hydrogen on the plates of a battery is known as.

Option A. polarization.

Option B. ionization.

Option C. hydration.

Correct Answer is. polarization.

Explanation. NIL ..................................

Question Number. 8. What part of a battery is covered in hydrogen during polarization

Option A. Anode.

Option B. Both the anode and the cathode.

Option C. Cathode.

Correct Answer is. Anode.

Explanation. NIL ..................................

Question Number. 9. Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery?. Option A. A high internal resistance condition. Option B. High current charging of the battery to more than 100 percent of its capacity. ... Option C. Excessive current draw from the battery. Correct Answer is. High current charging of the battery to more than 100 percent of its capacity. Explanation. Thermal runaway usually occurs on charging ..................................

Question Number. 10. The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking. Option A. the voltage with rated load switched ON. Option B. the voltage on open circuit. Option C. the voltage off load. Correct Answer is. the voltage off load. Explanation. If just checking the voltage (as opposed to a charge test) then the battery must be off load to prevent the internal resistance dropping the terminal voltage ..................................