ABA 0303

EXAM

ANSWER ANY THREE QUESTIONS

QUESTION ONEa) i. What is an electric current and what is the SI unit? (2 marks)

ii. What are the major components of an electric circuit? (2 marks)

iii. With the aid of a diagram, draw an electric circuit indicating the basic components and resistors connected in parallel. (4 marks)

iv. Show the formula of calculating the resistance of the resistors connected in parallel. (2 marks)b) From the diagram below answer all the questions given the following variablesR1=10R2=10R3=15R4=5R5 is the series combination of R4 and R5R6= R2

i. The total resistance of the circuit (2 marks)

ii. The power at the source (2marks)

iii. The current through R2 (2 marks)

iv. The voltage dropped across R6 (2 marks)

v. The current through R4 (2 marks)

QUESTION TWOi. An enclosed space requires air conditioninga) What do you understand by the term air conditioning?

b) Why would you recommend air conditioning for an enclosed space? (5 marks)ii. Outline:

a) The desirable qualities of air conditioning system (3 marks)

b) The basic difference between passive and active air conditioning system. Give example in each category (4 marks)

c) The factors to consider when choosing an air conditioning system (2 marks)

iii. Explain three types of air conditioning system and explain where they are best suited for usage

(21 marks)

QUESTION 3i. What is an electrical installation

(2 marks)

ii. With reference to fuses, define the following terms:

a) Fuse element

b) Current rating

(4 marks)

iii. What are miniature circuit breakers, and why are they preferred over fuses?(4 marks)

iv. With the aid of a well labeled diagram, explain the loop-in method for wiring a final circuit for lighting.

(10 marks)

QUESTION 4.

(a)

i. What is ventilation?

3 Marks

ii. What are the purposes of ventilation?

5 marks

(b)

i. Explain three examples of renewable energy and state their advantages and disadvantages.

12 marks

QUESTION 5.(a) (i)What is a lightining protection system?

2 Marks(ii) What are the hazards associated with direct lightning strikes?

4 Marks(iii) Define an earthing electrode and state the factors that affect its effectiveness, resistance, and surge impedance .

4 marks

(b) With the aid of a diagram, explain an electric cable and indicate the different parts.

5 marks

(c) What is the essence of protecting all electrical wiring systems and all electrical apparatus associated with wiring?

5marks