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Electrical Exam Questions.

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1. What is the force on a conductor which carries 10 Amps in a magnetic field with a flux density of 0.8 Tesla? The effective length of the conductor is 300mm.


2. The peak value of a sine wave is 350 Volts. Calculate:


i, The R.M.S. value.


ii, The average value of a half cycle.


iii, The peak to peak value.


3. An A.C. generator runs at 15 revs per second. It produces an R.M.S. output of 240 Volts at 60 Hz. If the speed is increased to 20 revs/second, state the effect on:


i, The Voltage output.


ii, The frequency.


iii, The periodic time.


4, Who said, "If chain still swinging, seat is still warm?


5. What is the modern name for what was historically called a "spur box?"


6. A card has 5 Amp, 15 Amp and 30 Amp fuse wire on it. What is it made of?


Z.


  • 0
    no 6 is cardboard


    Q2 ii needs to state which average you mean, mean, median, mode, RMS etc etc ("Average" is also the most dangerous word in the universe).


    2 i       247.5V

    2 iii      700v

    3   i none, +33% , -33%


    4 ?

    5  junction box?     

  • 0
    ebee:

    no 6 is cardboard


    Q2 ii needs to state which average you mean, mean, median, mode, RMS etc etc ("Average" is also the most dangerous word in the universe).


    2 i       247.5V

    2 iii      700v

    3   i none, +33% , -33%


    4 ?

    5  junction box?     

      


    Average? Oh ek! I suppose I mean that if four people all go out for a meal, and the separate bills come to £13.00, £14.50, £18.00 and £17.00 The average bill is 13.00 +14.50 +18.00 + 17.00 divided by four, pounds. The average is approx. £15.63.


    Z.




     


  • 0
    ebee:

    Q2 ii needs to state which average you mean, mean, median, mode ...


    Never mind that; which mean do you mean? Arithmetic, geometric or harmonic? ?


  • 0
    My advisor has just said that mean Voltage of a full sine waveform will equal zero because one value for a half cycle will be positive and the other negative for the other half cycle.  Also something about 0.637 for a half wave.


    Z.
  • 0
    ok mean is zero you got me on that one (arithmetical mean I should say)


    anyeway no 6 is cardboard
  • 0
    Zoomup:

    1. What is the force on a conductor which carries 10 Amps in a magnetic field with a flux density of 0.8 Tesla? The effective length of the conductor is 300mm.


    Answer = F=BLI, 


                         F = 0.8 X 0.3 X 10


                         F = 2.4 N.


    2. The peak value of a sine wave is 350 Volts. Calculate:


    i, The R.M.S. value.  Answer = 350 X 0.707

                                                           = 247.5 Volts.


    ii, The average value of a half cycle. Answer = 350 X 0.636

                                                                                       = 222.6 Volts.

                                                                    

    iii, The peak to peak value. Answer = 350 X 2


                                                                      + 700 Volts.


                                                     


    3. An A.C. generator runs at 15 revs per second. It produces an R.M.S. output of 240 Volts at 60 Hz. If the speed is increased to 20 revs/second, state the effect on:


    i, The Voltage output. Answer = Voltage will increase.


    ii, The frequency. Answer = Frequency will increase.


    iii, The periodic time. Periodic time will decrease.


    4, Who said, "If chain still swinging, seat is still warm? Answer = Benny Hill.


    5. What is the modern name for what was historically called a "spur box?"


    Answer = Fused connection unit.


    6. A card has 5 Amp, 15 Amp and 30 Amp fuse wire on it. What is it made of?


    Answer = Cardboard  or copper. Depending on which side of the river you come from.


    Z.


     


     


  • 0
    Chris Pearson:
    ebee:

    Q2 ii needs to state which average you mean, mean, median, mode ...


    Never mind that; which mean do you mean? Arithmetic, geometric or harmonic? ?




    According to the text book from which the questions originated mean is defined as:


    "The mean is the average of the numbers; a calculated "central" value of a set of numbers. To calculate the mean, just add up all the numbers of the set, then divide by how many numbers there are in the set."


    Z.


  • 0
    ebee gets today's star prize and an extra bottle of milk from the milk monitor for his hard work and excellent effort. You'll go far in life ebee. Your name also goes on the board of merit in the class room.


    Z.
  • 0
    Zoomup:
    Chris Pearson:
    ebee:

    Q2 ii needs to state which average you mean, mean, median, mode ...


    Never mind that; which mean do you mean? Arithmetic, geometric or harmonic? ?


     




    Arithmetic boy.  ARITHMETIC.  We are not building blinkin pyramids or playing the flute.                                                                                                                                                                                                                          According to the text book from which the questions originated mean is defined as:


    "The mean is the average of the numbers; a calculated "central" value of a set of numbers. To calculate the mean, just add up all the numbers of the set, then divide by how many numbers there are in the set."


    And, who has been over feeding the class hamster? It looks like a blinkin rugby ball.


    Z.




     


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