SQA

X025/11/01

*X025/11/01* ©

ELECTRONIC AND ELECTRICAL FUNDAMENTALSINTERMEDIATE 2

100 marks are allocated to this paper.

Answer all questions in Section A (50 marks).

Answer two questions from Section B (25 marks each).

In all your answers to questions requiring calculations, all working must be shown.

N A T I O N A LQ U A L I F I C A T I O N S2 0 1 5

W E D N E S D A Y , 3 J U N E9 . 0 0 A M – 1 1 . 3 0 A M

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Section A

Attempt all the questions in this section (50 marks)

1. Convert the following numbers.

(a) Binary to Decimal 100100012

(b) Decimal to Hexadecimal 18610

(c) Hexadecimal to Binary AE16

2. Identify the pin connections for the circuit symbols shown in Figure Q2(a) and Figure Q2(b).

(a)

1

2

3

Figure Q2(a)

(b)

1

2

3

Figure Q2(b)

3. The diagrams in Figure Q3 show input and output waveforms to and from electronic circuits labelled X and Y.

Figure Q3

State the full name of the function that is being performed by:

(a) circuit X;

(b) circuit Y.

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2

(3)

1

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(3)

4. For the circuit shown in Figure Q4:

C1

0 V

C3

C2

R1

R2

R3

VDD = +20 V

VOUT = 12 Vpk–pk

VIN = 400 mVpk–pk

at 1 kHz

1

2

3

Figure Q4

(a) state the circuit configuration;

(b) determine the circuit gain.

5. Figure Q5 shows a current carrying conductor placed between magnetic poles.

N S

Figure Q5

(a) State what direction the force acts upon the conductor.

(b) The length of conductor in the field is 0·4 m, the magnetic flux density is 0·2 T and a force of 1·6 N acts upon the conductor.

Determine the current.

[Turn over

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6. The diagram in Figure Q6 includes a variable resistor (RV) that can be varied between 20 kΩ and 50 kΩ.

VOUT

pk–pk

VIN = 0·4 Vpk–pk

10 kΩ

RV

Figure Q6

(a) State the phase relationship between input and output voltages.

(b) Determine the maximum value of output voltage (pk–pk).

(c) Determine the maximum value of resistor that could replace the 10 kΩ that would enable an output voltage of 4 V (pk–pk) to be achieved.

7. For the circuit shown in Figure Q7:

A

B

CZ

Figure Q7

(a) determine the Boolean expression for the circuit;

(b) construct the truth table;

(c) use the truth table to determine an alternative Boolean expression for the circuit.

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1

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1

1

(8)

2

2

2

(6)

8. For the circuit shown in Figure Q8, determine:

12 Ω

4 Ω

2 Ω

10 V

Figure Q8

(a) the total circuit resistance;

(b) the supply current;

(c) the current through the 12 Ω resistor;

(d) the circuit power;

(e) the energy consumed by the circuit in 10 minutes.

9. A door entry system is used to open a secure area that can only be opened between 8.30 am and 5.30 pm denoted by a logic 1 on input A. The door can be opened by two methods:

• whenthecorrectcodeisenteredviaanumerickeypaddenotedbyalogic1oninput B.

• whenanauthorisedswipecardisplacedinthecardslotdenotedbyalogic0on input C.

Note that the keypad and the swipe card cannot be used at the same time to open the door.

(a) Determine the logic expression for the entry system.

(b) Draw the truth table for the expression.

(c) Draw a logic diagram for the system using ANSI symbols.

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6

Section B

Attempt any TWO questions in this section (50 marks)Each question is worth 25 marks

10 (a) Add the following binary numbers.

(i) 00102 + 01012

(ii) 01012 + 00112

(b) State the Boolean expression and construct the truth table for the following logic gate.

&ABC

Figure Q10(b)

(c) Using the Worksheet for Q10(c) provided, select the required logic chips and sketch the required connections on the worksheet for the circuit shown in Figure Q10(c) to function correctly.

B C D

1

24

5

6 Z

3

Figure Q10(c)

(d) Draw, using BS symbols, the logic diagram for the following Boolean Expression and determine the truth table.

Z = (R + S + T ).(S + T)

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10. (continued)

(e) The circuit shown below, Figure Q10(e)(i), has developed a fault and upon testing, the outputs shown in the truth table Figure Q10(e)(ii) were obtained. Determine which gate (input or output) is at fault and state the nature of the fault.

A B C

1

2

3

4

5Z

TP1

TP2

Figure Q10(e)(i)

A B C TP1 TP2 Z

0 0 0 0 0 0

0 0 1 0 0 0

0 1 0 0 0 0

0 1 1 0 1 1

1 0 0 0 0 0

1 0 1 0 0 0

1 1 0 0 0 1

1 1 1 0 1 0

Figure Q10(e)(ii)

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11. (a) For the waveform shown in Figure Q11(a) determine:

0·30 ms

50 V40 V30 V20 V10 V

0−10 V−20 V−30 V−40 V−50 V

0·6 ms 0·90 ms 1·2 ms

Emf

Figure Q11(a)

(i) the peak value of the voltage;

(ii) the rms value;

(iii) the period of the waveform.

(b) (i) A coil of length 2·5 m is moved through a magnetic field of 0·25 mT at a speed of 10 m s−1. Calculate the induced voltage.

(ii) The same coil is now inserted in a magnetic field of 1·2 mT and is connected to a supply. Determine the current flowing in the conductor if the force on the conductor is measured at 0·4 N.

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11. (continued)

(c) For the circuit shown in Figure Q11(c) determine:

20 Ω

20 Ω

2 Ω 10 Ω

15 Ω

R1

R2

5A

1A3AR3

R4

VS

R6

R7

R5

Figure Q11(c)

(i) the supply voltage VS;

(ii) the total circuit resistance;

(iii) the value of resistor R4;

(iv) the voltage across resistor R6;

(v) the value of resistor R6.

(d) For the circuit shown in Figure Q11(d) determine:

8 A

2 A

R1 R2

R3

180 V

R4

10 Ω 5 Ω

Figure Q11(d)

(i) the power dissipated in the 10 Ω resistor R2;

(ii) the total power dissipated in the circuit;

(iii) the energy consumed, in joules, if the circuit is operated for 24 hours.

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12. (a) Identify the circuit shown in Figure Q12(a) and identify the purpose of each of the capacitors C1, C2 and C3.

C1

C2R1

R3

1·4 V

R4 C3

R2 6K8

1K5

hfe = 400

IC

Ib

VCC

12 V

0 V

6 V

Ideal transistor

Figure Q12(a)

(b) For the circuit shown in Figure Q12(a), calculate:

(i) the collector current Ic;

(ii) the base current Ib;

(iii) the current through the resistor R2;

(iv) the value of the resistor R1.

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12. (continued)

(c) For the circuit shown in Figure Q12(c):

R1

R2

RV50 K

10 K

VOUT = 550 mVVIN

3 6

52

1

Figure Q12(c)

(i) identify the circuit configuration shown in Figure Q12(c);

(ii) determine the gain of the circuit and the input voltage.

When setting up the circuit it is found that for an input of 0 V the output is not zero.

(iii) What component in Figure Q12(c) will allow the output to be adjusted to zero and what is this process called?

(d)

D1

20 V50 Hz

RL VOUT

C1

Sw1

Figure Q12(d)

Sketch the output waveform for the circuit shown in Figure Q12(d) with

(i) Sw1 open, and

(ii) Sw1 closed.

[END OF QUESTION PAPER]

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*X025/11/11*

X025/11/11

ELECTRONIC AND ELECTRICAL FUNDAMENTALSINTERMEDIATE 2Worksheet for Q10(c)

N A T I O N A LQ U A L I F I C A T I O N S2 0 1 5

W E D N E S D A Y , 3 J U N E9 . 0 0 A M – 1 1 . 3 0 A M

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[X025/11/11] Page two

[END OF WORKSHEET]

Worksheet for Question 10(c)

7400

7432

7404

+

+

+

(0V)

(0V)

(0V)

0 V 5 V A B C D