What are your hobbies? - Page 6 - Electrician Talk - Professional Electrical Contractors Forum

frank · 03-31-2007, 05:20 AM

Here is the last of the Master Electrician Examinations. Paper No 1. There were 2 other papers in the examination but they covered Regulations and Technical drawing. So not much point to show them here.

I looked at the questions again after some 30 years and to tell you the truth. If I took the examination now............I wouldn't pass.

PAPER No 1

Electrical Technology 1
(Units, Circuits & Measurements)

Answer any FIVE Questions
All questions carry equal marks
QUESTION 1
(a) State Kirchhoff’s Laws, and explain them with the aid of appropriate circuit
diagrams.
(b) A 2-wire distributor ABCDEF is fed at points A and F at 250V. d.c. Load currents
of 60, 100, 50 and 40 Amp. are taken at points B,C,D and E respectively, at
distances from end A of 50, 75, 100 and 150 yd respectively. The total length of distributor is 200 yd and the resistance per core per 1,000 yd length of distributor is 0.8
Calculate,
(i) the current in each section of the distributor
(ii) the voltage at each load point.
QUESTION 2
A pump raises 1,000 gal. of water per min against a total head of 30ft with an efficiency of 70%
It is driven by a 500V d.c. motor at 900 r.p.m. which has an efficiency of 85%
Calculate
(a) the required b.h.p. of the driving motor.
(b) the torque developed by the motor in Nw-m.
(c) the annual energy consumption if the pump operates at an average of
100 hr. per week throughout the year. (one gallon of water weighs 10 lbs)
QUESTION 3

(a) Sketch the hystereisis loop for a material suitable for use as armature
laminations, stating the main points regarding the shape.
(b) An electromagnet has a rectangular core of effective cross-sectional area
16cm2 and a mean magnetic length of 40cm.
If the exciting coil has 400 turns, calculate the current necessary to
produce a flux of 0.8 mWb in the air gap. The leakage coefficient is 1.2.
Corresponding values of B and H for the core material is as follows :-
B(Wb/m2) 0.15 0.36 .066 0.88 1.02
H(AT/m) 200 400 600 800 1000
Permeability of free apace = 1g = 4`x 10-7 ) H/m

QUESTION 4

(a) With reference to a dielectric medium explain what is meant by the terms
"relative permittivity" "electric flux-density" and "voltage gradient".
(b) Two capacitors having capacitances of 4Цf and 6цF respectively are
connected in series across a 120V d.c. supply. Calculate
(i) the p.d. across each capacitor
(ii) the energy stored in each capacitor
(iii) the equivalent capacitance of the two capacitors in series.

QUESTION 5
Explain how a moving-coil ammeter can be converted into an a.c. instrument by using :-
(a) a single-wave rectifier
(b) a full-wave bridge rectifier

A moving-coil ammeter is used, without being recalibrated, in a full-wave bridge rectifier circuit to measure a sinusoidal current of 2A(RMS). Calculate the reading on the ammeter.

QUESTION 6
A Wheatstone Bridge circuit is used to measure an unknown resistance. Draw this circuit and from it obtain an expression for the unknown resistance.
A Wheatstone Bridge circuit with ratio arms of 100ת and 1000 ת respectively was used to determine the value of an unknown resistor X. The value was found to be 362 ת. X being the arm adjacent to the 1000 ת.
It was later discovered that the value of the known variable resistor R taken in the calculation was 10 Q too large. Determine the correct value of X.

QUESTION 7
A resistor of 50 Q an inductor of 0.02H and a capacitor of 56.6ц F are connected in series across a 200 v 50 c/s supply.
Calculate.
(a) the current flowing
(b) power factor of the circuit

To what value must the frequency be adjusted in order to make the impedance of
the circuit 50ц
If the supply voltage remains unchanged determine the voltage across each
component at the new frequency.
QUESTION 8
(a) With the aid of circuit and vector diagrams deduce the relationship
between the line and phase voltages of a 3-phase, star-connected
system.
Consider balanced conditions and a symmetrical supply.
(b) Each phase of a delta load consists of an inductor of resistance 8 ת and
reactance of 6 ת in parallel with a capacitor of 318 ц F.
The supply is 415 V at 50 c/s.
Determine,

(i) current in each phase,
(ii) current in each line,
(iii) total power supplied.

Frank

Mountain Electrician · 03-31-2007, 06:39 AM

Wow...I've taken Masters exams in New Mexico (electrical contractor), Arizona, Wyoming and Colorado and none of them were even close to this. Those exams were a based more in code and service and load calcs. Are your masters exams still similar to this today? Seems more like an engineering exam than an electricians exam. I wouldn't pass. Nope..no way.

frank · 03-31-2007, 08:44 AM

This is the first page of the electricians examination I took at age 18. Apprenticeship began at age 15 and ended at 21. You took two compulsory examinations. Electricians at 18 and Advanced at 20. Masters were taken if and when you wished.

Now apprentices take modules instead of all year study and have to pass each module. Is it easier. Well old timers would say so.

Frank

frank · 03-31-2007, 08:48 AM

Trying for a bigger print picture

Frank

frank · 03-31-2007, 08:49 AM

Sorry lads. It's the best I can do.?

Frank

frank · 04-05-2007, 03:21 PM

If you were in the UK today you would be on statutory holiday until Monday. Better still if you were in the Construction Industry you would be on holiday with full pay until April 16th.
So since I had nothing to do today I took my vintage radios to a local antique market.

Here I am enjoying the sunshine. Have a good day!

Frank

Dembones · 04-05-2007, 10:28 PM

Work, school, Jeep, and occasionally I visit friends in college. Why not if mommy and daddy can afford it right? Anyway here's my project:

HCECalaska · 04-08-2007, 01:43 PM

my hobbies are fishing and building RC planes. i currently have about 12 planes ready to fly.

frank · 04-09-2007, 04:08 AM

Any chance of photographs of those RC planes?

Frank

HCECalaska · 04-09-2007, 10:49 PM

i need to resize them so they will load to the site. my pics are to big now .

JohnJ0906 · 04-09-2007, 11:08 PM

If you use a hosting site, you can always post a link

http://i125.photobucket.com/albums/p...2qualified.jpg

Greg · 09-08-2007, 03:11 PM

Thought I would dig up an old thread since I'm new to the board. Anything having to do with the outdoors. Hunting, fishing, and scubadiving-mainly spearfishing. I also tinker with wood working.

You gotta love living in Florida.

Some before and after pictures of my front door.

Pediment under construction

Greg · 09-08-2007, 03:14 PM

Installation prior to paint. It has since been painted high gloss oil-based pure white.

5 picture limit got me, had to make post a 2 parter.