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Weekend Quiz. Back to Basics.

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Q.1. There are two resistors in series in a circuit, of 18 Ohms and 22 Ohms resistance. The current through the 18 Ohm resistor is 6 Amps. Calculate the supply Voltage to the circuit.


Q.2 There are three resistors of resistance 20 Ohms, 10 Ohms and 8 Ohms connected in parallel to a 6 Volt D.C. supply. Calculate:


a, The total resistance.


b, The current taken from the supply.


Q.3. A coil of 30 Ohms reactance is connected to a 200 Volt A.C. supply circuit, in series with a of 50 Ohms resistance. A capacitor of 30 Ohms reactance is connected in series with the coil. Calculate,


a, The circuit impedance.


b, The current drawn from the supply.


c, The power used.


Q.4. An electric heater uses 5.4MJ in 45 minutes. What is the rating of the element?


a, 1kW.


b, 1.5kW.


c, 2kW,


d, 3kW.


Q.5 The input of an electric motor is 5.8kW. The output is 4.75kW. The efficiency is,


a, 1.05%


b, 10.5%


c, 82%


d, 122%


Z.


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  • 0
    AC Theory was drummed into me long before I went to sea. Q3 being a nice series resonant circuit.


    After leaving school in 1965, instead of going for ONC/OND etc as I had considered, I was talked into applying for a MoD position which included an intensive training course. So I must thank one of the Instructors there, a Mr Brocklebank, whose rendition of, “One Over Two Pi Root LC Gives You the Resonant Frequency” ensured that to this day I still remember this particular formulae. His other ability, being ambidextrous, was to write to the bottom of a section on the wall length blackboard with his left hand and then immediately start from the top of the next section using his right hand...
    The RAF Maintenance Command Civilian Technical Training School at RAF Sealand Dan Archer, occupied the buildings of the US Air Force prison which was on the RAF Sealand site during the American occupation of RAF Sealand between 1951 to 1957 when it was home to the 7558th Air Depot Group, 3rd Motor Transport and others. I can remember seeing into one of the cells, not very appealing. The cells then being used for storage of what looked like junk, although thinking back I can remember seeing what appeared to be the control stick of a World War 2 fighter aircraft.
    The bonus for being in an American designed building over the winter months was that there was central heating, excessive central heating in fact.
    I wonder why I receive strange looks when I say that I once spent 20 weeks in an American prison? Well, at least I came home every night!


    Clive




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  • 0
    AC Theory was drummed into me long before I went to sea. Q3 being a nice series resonant circuit.


    After leaving school in 1965, instead of going for ONC/OND etc as I had considered, I was talked into applying for a MoD position which included an intensive training course. So I must thank one of the Instructors there, a Mr Brocklebank, whose rendition of, “One Over Two Pi Root LC Gives You the Resonant Frequency” ensured that to this day I still remember this particular formulae. His other ability, being ambidextrous, was to write to the bottom of a section on the wall length blackboard with his left hand and then immediately start from the top of the next section using his right hand...
    The RAF Maintenance Command Civilian Technical Training School at RAF Sealand Dan Archer, occupied the buildings of the US Air Force prison which was on the RAF Sealand site during the American occupation of RAF Sealand between 1951 to 1957 when it was home to the 7558th Air Depot Group, 3rd Motor Transport and others. I can remember seeing into one of the cells, not very appealing. The cells then being used for storage of what looked like junk, although thinking back I can remember seeing what appeared to be the control stick of a World War 2 fighter aircraft.
    The bonus for being in an American designed building over the winter months was that there was central heating, excessive central heating in fact.
    I wonder why I receive strange looks when I say that I once spent 20 weeks in an American prison? Well, at least I came home every night!


    Clive




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