EASA Part 66 : Electrical Question4

Question Number. 37. What is the approximate internal resistance of a Leclanche cell?. Option A. 0.02 ohms - 4 ohms. Option B. 6 ohms - 10 ohms. Option C. 20 ohms - 30 ohms.

Correct Answer is. 0.02 ohms - 4 ohms. Explanation. A leclanche cell is just another name for the zinc-carbon cell. Its IR is more like 0.4 - 4 ohms. Some good info on the types of cells and their IRs at External website...

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. 20. What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5 hours?. Option A. 112.5 ampere-hour. Option B. 90.0 ampere-hour. Option C. 45.0 ampere-hour.

Correct Answer is. 112.5 ampere-hour. Explanation. Ampere.hours means amps * hours.

Question Number. 15. Two 12V 40 amp hour batteries connected in parallel will produce. Option A. 24V 80 ah. Option B. 12V 80 ah. Option C. 24V 40 ah.

Correct Answer is. 12V 80 ah. Explanation. NIL.

Question Number. 18. Two similar 12v batteries connected in parallel will produce. Option A. 24v e.m.f. with the same capacity as each battery. Option B. 12V e.m.f. with twice the capacity of each battery. Option C. 24V e.m.f. with twice the capacity of each battery

Correct Answer is. 12V e.m.f. with twice the capacity of each battery. Explanation. Batteries in parallel - voltage remains the same but the current rating is increased.

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. 45. A 24V 40AH battery discharges at 200mA. How long will it last?. Option A. 400 hours. Option B. 300 hours. Option C. 200 hours.

Correct Answer is. 200 hours. Explanation. 200mA goes into 1A-5 times. 5 * 40 = 200 hours.

Question Number. 16. A 24-volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?. Option A. 12 volts. Option B. 24 volts. Option C. 3 volts.

Correct Answer is. 24 volts. Explanation. Resistors ion parallel, voltage across each one is the same and equal to the source voltage (if nothing else is in series with them).

Question Number. 11. Two batteries 12V and 40 Ah each, are in series. What is the total capacity?. Option A. 12V 80 Ah. Option B. 24V 40 Ah. Option C. 24V 80Ah.

Correct Answer is. 24V 40 Ah. Explanation. Batteries in series - voltage increases but capacity remains the same (vice versa if they were in parallel).

Question Number. 44. Two 12V, 40Ah cells in series gives. Option A. 24V 80Ah. Option B. 12V 40Ah. Option C. 24V 40Ah.

Correct Answer is. 24V 40Ah. Explanation. Cells in series, voltage doubles, Amp hour rating remains the same.

Question Number. 26. Two 2 volt 10AH cells are connected in series, the output voltage and the capacity would be. Option A. 4 volt 10 AH. Option B. 4 volt 20 AH. Option C. 2 volt, 20 AH.

Correct Answer is. 4 volt 10 AH. Explanation. Batteries in series - voltage doubles, but the rating stays the same.

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. 54. For how many hours will a 140AH battery deliver 15A?. Option A. 9.33 hours. Option B. 27.25 hours. Option C. 15.15 hours.

Correct Answer is. 9.33 hours. Explanation. 15 * H = 140, H = 9.33 hrs.

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. 32. In a thermocouple, where is voltage measured?. Option A. At both junctions. Option B. At the hot junction. Option C. At the cold junction.

Correct Answer is. At the cold junction. Explanation. The voltmeter measures the voltmeter across the cold junction of a thermocouple.

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. 35. A battery's internal resistance is determined by (OCV = Open Circuit Voltage, CCV = Closed Circuit Voltage). Option A. IR = (OCV - CCV)/ i. Option B. IR = (OCV + CCV) / i. Option C. IR = (OCV - CCV) / V.

Correct Answer is. IR = (OCV - CCV)/ i. Explanation. Internal resistance (IR) has no effect on output voltage when Open Circuit. So Open Circuit Voltage (ocv) is higher than Closed Circuit Voltage (ccv). Using ohm's law (R=V/I), IR = (ocv) - ccv) all divided by current.

Question Number. 40. To generate electricity with a fuel cell, you need a constant supply of. Option A. Nitrogen & Sunlight. Option B. Oxygen & Hydrogen. Option C. Kerosene & Heat.

Correct Answer is. Oxygen & Hydrogen. Explanation. http://www.fuelcells.org/whatis.htm

Question Number. 47. When light energises a component, what is the component?. Option A. Light emitting diode. Option B. Photodiode. Option C. Laser diode.

Correct Answer is. Photodiode. Explanation. NIL.

Question Number. 39. What effect does hydrogen have in a battery cell?. Option A. Sulphation. Option B. Nothing. Option C. Polarization.

Correct Answer is. Polarization. Explanation. Hydrogen, if allowed to form on the anode, reduces the battery output. This is polarization.

Question Number. 52. When the battery is connected to the aircraft, which terminal should you connect first?. Option A. Any. Option B. Positive. Option C. Negative.

Correct Answer is. Positive. Explanation. Aircraft Electricity and Electronics Eismin Page 43.

Question Number. 14. In a voltaic cell, what is the build-up on the cathode called?. Option A. Hydration. Option B. Polarization. Option C. Sulphation.

Correct Answer is. Sulphation. Explanation. Polarization is build-up of hydrogen on the ANODE. Sulphation however, is build-up of lead-sulphate on BOTH anode and cathode.

Question Number. 57. What is the internal resistance of a battery?. Option A. The resistance measured across the two terminals. Option B. The resistance measured when the battery is half charged. Option C. The resistance present inside the battery while connected to a load.

Correct Answer is. The resistance present inside the battery while connected to a load. Explanation. Aircraft Electricity and Electronics page 33.

Question Number. 55. What part of a nickel-cadmium cell helps to prevent thermal runaway?. Option A. The separator. Option B. The negative plate. Option C. The positive plate.

Correct Answer is. The separator. Explanation. Aircraft Electricity and Electronics Eismin Page 47 2nd para.

Question Number. 34. The capacity of a battery is measured in. Option A. volts. Option B. ampere-hours. Option C. cubic centimetres.

Correct Answer is. ampere-hours. Explanation. Battery capacity is in amperehours.

Question Number. 13. Conventional current flow inside a battery is from. Option A. either anode to cathode or cathode to anode, depending on the active elements. Option B. cathode to anode. Option C. anode to cathode.

Correct Answer is. anode to cathode. Explanation. The cathode is positive. Conventional current flows from positive to negative on the external circuit, but to close the circuit must flow negative to positive INSIDE the battery.

Question Number. 33. Mercury cells are covered with a metal cover. Option A. as a protective cover. Option B. as a negative terminal. Option C. as a positive terminal.

Correct Answer is. as a positive terminal. Explanation. The outer cover (or case) of a mercury cell is the positive terminal - Have a look at your watch or calculator battery to verify.

Question Number. 38. An aircraft battery on charge from the aircraft generators causes. Option A. battery voltage to increases to nominal voltage and the charge current decreases. Option B. internal resistance of the battery to decrease in sympathy with the decreasing charging current. Option C. battery voltage to decrease to zero until it is fully charged.

Correct Answer is. battery voltage to decrease to zero until it is fully charged. Explanation. As the battery voltage increases, the current charging it decreases.

Question Number. 41. A ni-cad battery found to be below normal capacity should. Option A. have its electrolyte adjusted. Option B. be removed and used for ground use only. Option C. be re-charged with a freshening charge.

Correct Answer is. be re-charged with a freshening charge. Explanation. See Jeppesen's Aircraft Batteries.

Question Number. 29. In a simple voltaic cell, polarization reduces output voltage because of the. Option A. build up of hydrogen on the cathode. Option B. transfer of material between the anode and the cathode. Option C. build up of hydrogen on the anode.

Correct Answer is. build up of hydrogen on the anode. Explanation. NIL.

Question Number. 50. A primary cell. Option A. can not recharged. Option B. can be recharged but only a few times. Option C. can be recharged.

Correct Answer is. can not recharged. Explanation. NIL.

Question Number. 51. If the insulation resistance of a lead/acid battery is down, it indicates. Option A. case leakage. Option B. leakage between positive and negative terminals. Option C. intercell leakage.

Correct Answer is. case leakage. Explanation. NIL.

Question Number. 25. The electrolyte in a nicad battery would rise if the battery was. Option A. remaining at constant voltage. Option B. charging. Option C. discharging.

Correct Answer is. charging. Explanation. The physical level of electrolyte drops a as Ni-Cad battery discharges.

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. 31. The Daniel Cell electrodes are. Option A. copper and zinc. Option B. carbon and zinc. Option C. zinc and manganese dioxide.

Correct Answer is. copper and zinc. Explanation. The Daniel Cell was an improvement on the first ever cell made by Voltaire. Both used copper and zinc electrodes.

Question Number. 19. The voltage of a secondary cell is. Option A. determined by the active materials on the plates. Option B. determined by the number of plates. Option C. determined by the area of the plates.

Correct Answer is. determined by the active materials on the plates. Explanation. Voltage of a battery is determined by what the plates are made from, and how many plates are in series. However, a 'cell' is not a battery and can only ever have two plates.

Question Number. 46. The electrolyte level of a ni-cad battery. Option A. falls during charge. Option B. falls during discharge. Option C. rises during discharge.

Correct Answer is. falls during discharge. Explanation. The electrolyte level of a nicad battery falls during discharge (but the s.g. remains constant).

Question Number. 42. In cold weather, to prevent the electrolyte freezing, a battery must be kept. Option A. fully charged. Option B. does not matter. Option C. fully discharged.

Correct Answer is. fully charged. Explanation. Checkout www.amplepower.com/primer/winter/.

Question Number. 21. If a nicad battery is not to be used immediately it should be stored. Option A. dry. Option B. fully charged. Option C. fully dissipated.

Correct Answer is. fully dissipated. Explanation. Ni-cad batteries must be stored fully discharged. Often with a metal bar across their terminals to ensure they are fully dissipated.

Question Number. 30. When the temperature of the electrolyte in a battery increases, the SG. Option A. remains the same. Option B. goes up. Option C. goes down.

Correct Answer is. goes down. Explanation. Volume rises with temperature, but mass does not. SG is a measure of the electrolyte density (which is mass / volume).

Question Number. 23. To improve the life of a dry cell it would be manufactured with. Option A. more electrolyte paste. Option B. more zinc. Option C. a pure carbon positive rod.

Correct Answer is. more zinc. Explanation. The zinc (negative electrode or cathode) gets eaten away.

Question Number. 12. If a battery has got low internal resistance, then the. Option A. no load voltage will be the same as on load voltage. Option B. on load voltage will be greater than no load voltage. Option C. no load voltage will be greater than on load voltage.

Correct Answer is. no load voltage will be greater than on load voltage. Explanation. The internal resistance will always drop the voltage and reduce the terminal voltage. It is the same whether it is high or low internal resistance - just a matter of 'how much'.

Question Number. 48. Formation of white crystals of potassium carbonate on a properly serviced Ni-cd battery indicates. Option A. over charged. Option B. full charged. Option C. under charged.

Correct Answer is. over charged. Explanation. NIL.

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. 27. The electrolyte in a nicad battery is. Option A. potassium hydroxide. Option B. nickel hydroxide. Option C. cadmium hydroxide.

Correct Answer is. potassium hydroxide. Explanation. NIL.

Question Number. 53. An ammeter in a battery charging system is for the purpose of indicating the. Option A. rate of current used to charge the battery. Option B. amperage available for use. Option C. total amperes being used in the aeroplane.

Correct Answer is. rate of current used to charge the battery. Explanation. Whilst charging (as the question says) the ammeter shows current flow TO the battery.

Question Number. 24. In a simple voltaic cell the collection of ions on the cathode causes. Option A. polarisation. Option B. sulphation. Option C. hydration.

Correct Answer is. sulphation. Explanation. The formation of lead sulphate on both plates of a lead acid battery is called SULPHATION.

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. 36. There are more negative than positive plates in a lead acid battery because. Option A. it is necessary for chemical action to take place. Option B. it reduces the internal resistance of the cell. Option C. the positive plates are prone to warping if the chemical action is taking place only on one side.

Correct Answer is. the positive plates are prone to warping if the chemical action is taking place only on one side. Explanation. A lead acid battery normally has one more negative plate than positive plate because the positive plates are prone to warping if the chemical action is taking place only on one side.

Question Number. 22. In a mercury cell the steel casing is. Option A. the negative terminal. Option B. neither. Option C. the positive terminal.

Correct Answer is. the positive terminal. Explanation. The 'outer can' is in contact with the zinc anode, which is positive.

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. 43. The internal resistance of a battery off load compared to on load is. Option A. the same. Option B. increased. Option C. decreased.

Correct Answer is. the same. Explanation. Internal resistance is constant, regardless of load.

Question Number. 17. The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking. Option A. the voltage on open circuit. Option B. the voltage off load. Option C. the voltage with rated load switched ON.

Correct Answer is. the voltage off load. Explanation. Assuming it is just a voltage check (and not a charge test) then it must be off load when carrying out the test. Otherwise the internal resistance will drop the voltage by an amount which varies according to the external load.

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.

Question Number. 56. When charging current is applied to a nickel-cadmium battery, the cells emit gas only. Option A. when the electrolyte level is low. Option B. if the cells are defective. Option C. toward the end of the charging cycle.

Correct Answer is. toward the end of the charging cycle. Explanation. EEL/1-3 4.5.5.

Question Number. 49. Thermal runaway causes. Option A. violent gassing only. Option B. violent gassing, boiling of electrolyte and melting of plates and casing. Option C. no gassing, but boiling of electrolyte and melting of plates and casing.

Correct Answer is. violent gassing, boiling of electrolyte and melting of plates and casing. Explanation. NIL.

Question Number. 28. In a Leclanche cell the plates are made of. Option A. mercury and lithium. Option B. nickel and cadmium. Option C. zinc and carbon.

Correct Answer is. zinc and carbon. Explanation. NIL.