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EASA Part 66 : Electrical Question9
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EASA Part 66 : Electrical Question9
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EASA PART 66 : ELECTRICALQUESTION9 WITH SOLVED QUESTIONS
AND ANSWERS
dQuestion Number. 1. A capacitor is fully charged after 25 seconds to a battery voltage of 20 Volts. The
battery is replaced with a short circuit. What will be the voltage across the capacitor after one time
constant?.
Option A. 0 volts.
Option B. 7.36 volts.
Option C. 12.64 volts. - Correct Answer is. 7.36 volts.
Explanation. The capacitor is discharging - so it discharges 63.2% in one time constant - so what is left?.
Question Number. 2. The voltage rating of a capacitor is.
Option A. the max voltage that can be constantly applied.
Option B. the min voltage required to charge.
Option C. the normal operating voltage. - Correct Answer is. the max voltage that can be constantly
applied.
Explanation. Exceed the voltage at which the capacitor is rated, and you destroy the capacitor.
Question Number. 3. The relative permittivity of a capacitor is.
Option A. the permittivity of the dielectric.
Option B. the relative permittivity of the dielectric in relation to a vacuum.
Option C. the permittivity of dielectric in relation to dry air. - Correct Answer is. the relative permittivity
of the dielectric in relation to a vacuum.
Explanation. 'Relative' means relative to 'free space' (a 'vacuum' in other words).
Question Number. 4. When checking a capacitor with an ohmmeter, if the reading shows charging but
the final reading is less than normal then the possible fault is a.
Option A. leaking dielectric capacitor.
Option B. short circuit dielectric.
Option C. open circuit dielectric. - Correct Answer is. leaking dielectric capacitor.
Explanation. NIL.
, Question Number. 5. Three capacitors 10 microfarads, 10 nanofarads and 10 millifarads are connected in
parallel. What is the total capacitance?.
Option A. 10.01001 millifarads.
Option B. 111 millifarads.
Option C. 1.001001 millifarads. - Correct Answer is. 10.01001millifarads.
Explanation. The biggest capacitor of the three is the 10 milliFarad. The other two are fractions of one
milliFarad. So the answer must be 10.**** milliFarad (no sums required).
Question Number. 6. If a 1milliFarad capacitor has a potential difference across it of 5V, what is the
energy stored?.
Option A. 12.5 Joules.
Option B. 12.5 milliJoules.
Option C. 25 mJoules. - Correct Answer is. 12.5 mJoules.
Explanation. Energy stored in a capacitor = 1/2 C V-squared (only the V is squared).
Question Number. 7. A capacitor with double the area and double the dielectric thickness will have.
Option A. double the capacitance.
Option B. the same capacitance.
Option C. half the capacitance. - Correct Answer is. the same capacitance.
Explanation. Get the formula for capacitance of a capacitor.
Question Number. 8. An electrolytic capacitor is used where.
Option A. minimum losses are essential.
Option B. there is a polarized input.
Option C. high frequency AC is used. - Correct Answer is. there is a polarized input.
Explanation. Wiring an electrolytic capacitor wrong polarity will destroy it. AC will therefore destroy it.
Current must be DC (i.e. polarised) and the right way.
Question Number. 9. What must you do to make a 3 F capacitor circuit into a 2 F circuit?.
Option A. Put a 2 F capacitor in parallel.
Option B. Put a 6 F capacitor in series.
Option C. Put a 1 F capacitor in series. - Correct Answer is. Put a 6 F capacitor in series.
Explanation. To reduce the capacitance of a circuit you must place a capacitor in series (formula is same
as resistors in parallel). You do the maths to see which one it is.
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