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BASIC ELECTRONICS – November 2021

BASIC ELECTRONICS – November 2021

Time: 3 hours

THE KENYA NATIONAL EXAMINATIONS COUNCIL
CRAFT CERTIFICATE IN INFORMATION TECHNOLOGY
BASIC ELECTRONICS

INSTRUCTIONS TO THE CANDIDATE

This paper consists of Section A and Section B.

  • Answer ALL questions in Section A and ANY FOUR questions from Section B.
  • Candidates should answer the questions in English.

SECTION A (40 Marks)

Answer ALL questions in this section.

  1. Define each of the following terms used in basic electronics:
    (i) Transformer – A device that transfers electrical energy between two or more circuits through electromagnetic induction.
    (ii) Load – An electrical component or portion of a circuit that consumes electric power.
    (iii) Electron – A subatomic particle with a negative electric charge.
    (iv) Resistance – The opposition that a substance offers to the flow of electric current.
  2. Explain each of the following terms as used in logic electronics:
    (i) Error clock – A signal used in digital electronics to correct timing or synchronization errors.
    (ii) NOT gate – A logic gate that outputs the opposite value of its input.
  3. Determine the resistance of each of the following resistor’s color codes (Magnitude):
    (i) Red, black, yellow, gold – 200kΩ ± 5%
    (ii) Purple, green, blue, silver – 75.6MΩ ± 10%
  4. Using one’s complement, work out 11100010 – 10110111:
    Answer: 00101011
  5. Explain two characteristics of Read-Only Memory (ROM):
  • Non-volatile: Retains data when power is turned off.
  • Pre-programmed: Data stored during manufacturing or writing processes.
  1. Outline four disadvantages of semiconductor components:
  • Sensitive to temperature changes.
  • Susceptible to radiation.
  • Limited power capacity.
  • Can be easily damaged by over-voltage.
  1. Convert the following numbers to their Gray code equivalent:
    (i) 11112 – 1011
    (ii) 10162 – 1111
  2. Determine the octal equivalent for each of the following number systems:
    (i) 206 – 3168
    (ii) 13910 – 2138
  3. Explain each of the following terms as used in number systems:
    (i) Logical shift – A bitwise operation that shifts bits to the left or right, filling with zeros.
    (ii) Binary mask – A bit pattern used to select specific bits from another bit pattern.
  4. With the aid of a diagram, describe the N-type semiconductors:
    Answer: N-type semiconductors are created by doping pure silicon or germanium with a pentavalent element, introducing extra electrons as charge carriers.

SECTION B (60 Marks)

Answer ANY FOUR questions from this section.

  1. (a) (i) Evaluate the following octal arithmetic, 6418 × 138:
    Answer: 107888

(ii) Differentiate between an ammeter and a voltmeter:

  • Ammeter: Measures current in amperes.
  • Voltmeter: Measures voltage in volts.
  1. Figure 1 shows an AC circuit. State the function of the parts labeled (i) and (ii):
    (i) Capacitor – Stores electrical energy in an electric field.
    (ii) Inductor – Stores energy in a magnetic field.
  2. List four types of resistors:
  • Fixed resistors.
  • Variable resistors.
  • Thermistors.
  • Light-dependent resistors (LDR).
  1. Convert the following numbers into their decimal equivalent:
    (i) F07914516 – 251647181
    (ii) 1010112 – 4310
  2. Differentiate between reverse bias and forward bias as used in semiconductor diodes:
  • Reverse bias: Increases the depletion region, preventing current flow.
  • Forward bias: Reduces the depletion region, allowing current flow.

Explain two circumstances that necessitate the use of NAND gates in circuits:

  • To simplify circuit design.
  • To implement universal logic functions.
  1. Outline three factors affecting the resistance of a wire/conductor:
  • Material of the conductor.
  • Length of the wire.
  • Cross-sectional area.
  1. Simplify the following Boolean algebra expression:
    (i) (A + B)(A + C) = A + BC
    (ii) AB + A(B + C) =A + BC

End of Paper