# Past Papers Basic Electrical Technology

## Guess Paper 1: Basic Electrical Technology Fall – 2020 Past Papers

University Name – Confidential

NOTE: Q.1 is compulsory, attempt any four questions from the remaining. All questions carry equal marks. Phones and other Electronic Gadgets are not allowed.

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 True/False

a. A step-up transformer has more turns in its secondary winding then its primary winding.
b. Electric current is the rate of flow of charge.
c. Ohm’s law states that voltage is directly proportional to current.
d. The capacitor is an electrical device that can store electrical charge.
e. The circuit in which current flow is equal to zero is called open circuit.
f. KVL states that the algebraic sum of all voltage around a closed loop is zero.
g. Current is measured in a unit called Ampere.

Q.2 Explain Ohm’s law in detail.

Q.3 Explain transformer with help of proper circuit diagram also explain step down transformer.

Q.4 Derive equation for current divider rule.

Q.5 What is capacitor also explain series combination of capacitors.

Q.6 Explain Kirchhoff’s current law (KCL) and also Kirchhoff’s voltage law (KVL) with proper diagram.

Q.7 What do you mean by filters also explain low pass filter with diagram.

Q.8 Write short notes on any two of the following

a) Power and energy
b) Current and Voltage
c) Circuit Breakers

## Guess Paper 2: Basic Electrical Technology F- 2020 Past Papers

University Name – Confidential

NOTE: Q.1 is compulsory, attempt any four questions from the remaining. All questions carry equal marks. Phones and other Electronic Gadgets are not allowed.

Time Allowed: 3 hours

Examination:   Final, Spring- 2020

Total Marks:    70, Passing Marks (35)

Q1. (a) A capacitor an inductor and resistor of 100 µF, 130mH and 150Ω are connected in parallel across a
220 V, 50 Hz single Phase supply.
Calculate: (I) Total impedance of the circuit. (II) Currents in current in each branch.
(b) Calculate the values of IA, IB and IC in the circuit given below.

Q2. The primary and secondary windings of a 500 kVA,11kV/400V transformer have resistances of 0.42Ω
and 0.0019Ωrespectively. The core loss is 2.9 kW, assuming the power factor of the load to be 0.8.

Q3. A single-phase motor operating of a 400 V, 50 Hz supply is developing 10 kW with an efficiency of 84% at a power factor of 0.7 lagging. Calculate: (a) the input apparent, real and reactive power.

Q4. Explain the construction of 3-phase AC motors with diagram.

Q5. (a) Explain bandwidth and selectivity of parallel RLC filter circuits.
(b) Draw and explain band-stop filters.

Q6. Explain the different components of switchgear system in detail.

Q7. (a) Draw and explain load-line for transistor amplifier.
(b) Explain common-base transistor amplifier.
Q8. Write short note on any two of the following
A. Form Factor of sinusoidal signals.
B. Power triangle.
C. Electric traction.

## Guess Paper 3: Basic Electrical Technology Spring- 2019 Past Papers

University Name – Confidential

NOTE: Q.1 is compulsory, attempt any four questions from the remaining. All questions carry equal marks. Phones and other Electronic Gadgets are not allowed.

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q1. A capacitor of 100 µF and a 150Ω resistance are connected in parallel across a 220 V, 50 Hz single
Phase supply.
Calculate: (I) Total impedance of the circuit. (II) Currents in resistance & capacitance.

Q2. (a) Derive an equation for the condition of maximum efficiency of Transformer.
(b) Explain the phenomena of resonance in parallel RLC Circuits.

Q3. The primary and secondary windings of a 1MVA, 50Hz, 11KV/410V transformer have resistances
of 1.5Ω and 3Ω respectively. The Core Loss is 9.2KW. Assuming the P.F 0.85,

Q4. Discuss how a low pass and a high pass filters can be designed using RC Circuit.

Q5. (a) Explain common-Emitter configuration of Bipolar Junction Transistor.
(b) Explain the difference between BJT & FET.

Q6. A 3-phase induction motor is supplied from a 50Hz system. The motor has a rotor frequency of 2.6Hz.
Calculate (i) Percentage slip. (ii) Speed of rotor in RPM.

Q7. An ideal 100KVA transformer has 500 turns on the primary and 40 turns on the secondary winding.
Primary side is connected to a 11KV, 50Hz supply. Calculate:
(i) Primary and secondary currents on full-load. (ii) Secondary E.M.F. (iii) Maximum flux in the Core.

Q8. Write short note on any two of the followings;
a) Voltage Divider Rule.
b) Kirchoff’s Laws.
c) Power Triangle.