NABTEB Basic Electricity Questions 2024 Objective and Theory Update
– NABTEB Basic Electricity Questions –
NABTEB Basic Electricity Questions will guide you before taking part in the NABTEB exams. Basic Electricity NABTEB Expo Questions are out now on our website.
NABTEB is one of the examination bodies set up by the Federal Government in 1992 to reduce the burden of conducting examinations, which involves a lot of technical and trade-related practicals.
The board conducts the National Technical Examination (NTC), National Business Certificate (NBC) and their respective advance level examinations (ANBC and ANTC).
NABTEB Basic Electricity Questions and Answers 2024
QUESTION 1
(a) State the symbol and the numerical meaning of the following:
(i) Pico
(ii) Micro
(iii) Milli
(iv) Mega
(v) Kilo
b. A 400ïF capacitor is charged by a steady current of 0.4A Flowing for 6 seconds.
(i) Calculate the final value of the charge stored in the capacitor and the p.d between its plates.
(ii) If the capacitor is subsequently discharged in 60 microseconds. Calculate the average discharged current.
QUESTION 2
(a) Define the following and give TWO examples of each (i) Insulator (ii) Conductor
(b) An orange of mass 50g falls from rest from a height of 40m. Calculate the kinetic energy of the orange after falling a distance of 25m. (Neglect air resistance Take g = 10m/S2 ).
SOLUTION
(i) An insulator is a material that does not allow electrons to pass through it freely. It is therefore a non-conductor of heat and electricity. Examples are plastic, wood, paper, silk, wool, e.t.c.
(ii) A conductor is a material that allows charges to pass through it freely. It is therefore called conductor of heat and electricity. Examples are metals, the human body, the earth, electrolytes, e.tc.
QUESTION 3
(a) Describe briefly, with the aid of sketches how an autotransformer differs from a double-wound transformer.
(b) Give ONE advantage and ONE disadvantage of the autotransformer compared with a double-wound transformer
(c) Calculate how many coulombs of electricity flow around a circuit when a current of 10A flows for 30 seconds.
QUESTION 4
(a) A purely capacitive circuit of 31.8ïF is connected to a 240V 50HZ supply. Calculate the capacitive reactance and the circuit current.
(b) List THREE types fluxes and FOUR advantages for using it is soldering work.
SOLUTION
b. Three types of fluxes
(i) Pure amber Resin
(ii) Activated Resin and
(iii) Fluxite
(iv) Killed spirit
Four advantages for using fluxes in soldering works:
i. It helps to remove oxide film from the surface of the conductor
(presents oxidation)
ii. It helps to prevent the oxide film from re-formation (prevents
corrosion)
iii. Helps to keep the joints wet
iv. Helps as a cleaning agent
v. Helps for easy flow of solder over the joints (Any four)
QUESTION 5
(a) What is a Resistor? Give its symbol
(b) List THREE types of Resistors
(c) Three resistors of values 15ï—, 20ï— and 30ï— are connected in series. If a voltmeter connected across the 20ï— resistor reads 90V, calculate:
(i) total resistance of the circuit
(ii) current in the 30ï— resistor
(iii) Voltage drop in the 15ï— resistor
(iv) Power consumed by the circuit
QUESTION 6
(a) Define capacitance and state its unit of measurement
(b) Enumerate FOUR types of capacitors
(c) Three capacitors of values 5ïf, 15ïf and 30ïf are connected in series. Another capacitor of value 50 if is connected in parallel with the series group across a 200V d.c. source. Calculate.
(i) Total capacitance of the series group
(ii) total capacitance of the circuit
(iii) total charge stored in the capacitor
(iv) energy stored by the 50 if capacitor
SOLUTION
4a. The ability of a capacitor to store electric charges is known as capacitance. It can also be defined as the ratio of the amount of electricity (charge), Q transferred from one plate to the other, to the potential difference produced between the plates. The symbol is C and it is given as C = Q/V The unit of measurement of the capacitance is Farad F (coulomb per volt).
4b) Types of Capacitors
(i) Paper capacitor
(ii) Electrolytic capacitor
(iii) Ceramic capacitor
(iv) Silver mica capacitor
(v) Polyester capacitor & poly carbonate capacitor
(vi) Tantalum capacitor
(vii) Polystyrene capacitor
QUESTION 7
(a) Define the following terms in relation to alternating current and state their symbols
(i) inductive reactance
(ii) impedance
(b) A 200ïf capacitor is connected in series with a 60ï— resistor.
The combinations is connected to a 200V, 50Hz supply.
Calculate:
(i) capacitive reactance of the capacitor
(ii) inpendance of the circuit
(iii) current
(iv) power factor
SOLUTION
a(i) Inductive Reactance is the opposition to alternating current due to the presence of an inductor in the circuit. It is given as XL and can be obtained from the relationship that, XL = 2Ï€fL. The symbol is XL and its unit is ohms.
a(ii) Impedance is the effective or total opposition to alternating current due to the presence of an inductance coil (an inductor), the capacitor and a resistor in an A.C. circuit. The impedance is represented with a symbol Z and its unit is ohms.
QUESTION 8
a. (i) State ONE application of a capacitor
(ii) Capacitors 8ïf, 12ïf and 20ïf are connected in a circuit
Calculate the resultant capacitance when connected in:
(i) Series
(ii) Parallel
b. State the factors which affect the resistance of a conductor
QUESTION 9
a. (i) Define electromotive force
(ii) State the unit and symbol of electromotive force
b. A dry cell of emf 3v and an internal resistance of 0.5ï— is connected to a
load resistance of 7ï— calculate
(i) the load current
(ii) the voltage drop across the internal resistance
QUESTION 10
a. State the factors which affect the resistance of a conductor
b. Determine the range of resistance of a resistor which has the following colour codes; Blue, Black Red and Silver
c. Two resistance of values 10ï— and 20ï— are connected in parallel across a 240v battery
(i) The total resistance
(ii) The total current
(iii) The energy consumed in the 12ï— resistor
SOLUTION
a. Factors that affect the resistance of a conductor
The nature of the conductor
The length of the conductor
The cross-sectional area of the conductor
The temperature of the conductor
The resistively of the conductor
QUESTION 11
a. i. Define capacitance
ii. State the THREE factors that determine the capacitance of a capacitor
b. Three capacitors of values 6ïf, 10ïf and 14ïf respectively are connected in series across 10V d.c source. Determine
(i) The total capacitance of the group
(ii) The total charge stored by the capacitors
(iii) The energy stored in the circuit.
DISCLAIMER! These are not real NABTEB Basic Electricity questions but likely repeated questions over the years to help candidates understand the nature of their examinations. Ensure to take note of every question provided on this page.
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