Mumbai University FE Sem 1 Basic Electrical & Electronics Engineering (ESC102) Question Paper December 2025

Q.1 (a) State the condition of maximum power transfer in a circuit and write the expression for maximum power.

Q.1 (b) Find RMS value of current flowing through a 314 μF capacitor when connected to 230 V, 50 Hz, single phase AC supply. Write the equation of instantaneous voltage and current.

Q.1 (c) How an actual (practical) transformer differs from an ideal transformer?

Q.1 (d) Compare single-phase and three-phase induction motors.

Q.1 (e) Explain working of a LED.

Q.2 (a) Find the current through 8 Ω resistance using Thevenin's Theorem.

[Circuit diagram: printed as an almost completely black (over-darkened) box in the source scan; element values and connections cannot be read — partly illegible in the source scan.]

Q.2 (b) Explain the construction and working principle of a BLDC motor.

Q.3 (a) A voltage e(t) = 100 sin 314 t is applied to a series circuit consisting of 10 Ω resistance, 0.0318 H inductance and a capacitor of 63.6 μF. Calculate (i) impedance of a series circuit, (ii) expression for i(t), (iii) power factor (iv) active power, reactive power, and apparent power of a series circuit.

Q.3 (b) Draw the characteristics of Zener diode and Explain application of a Zener diode as a voltage regulator

Q.4 (a) Find Current through 4 Ω resistance using Nodal analysis

[Circuit: a common bottom wire (reference). Left branch: a 6 V battery (longer plate, +, at the top) in series with a 3 Ω resistor, going up from the bottom wire to the top-left corner; the top wire runs right to node A. From A a 6 Ω resistor goes down to the bottom wire. Between A and node B (top wire) is the 4 Ω resistor. From B a 2 Ω resistor goes down to the bottom wire. The top wire continues from B to the right, where a 5 A current source (drawn as a filled circle, no arrow shown) is connected between the top-right corner and the bottom wire.]

Q.4 (b) Explain CE configuration of BJT with the input and output characteristics.

Q.4 (c) Three identical coils each [4.2 + j5.6] Ω are connected in star across 415 V, three-phase, 50 Hz, AC supply. Determine (a) the line current (b) the power factor and (c) the total power.

Q.5 (a) Explain the construction and working principle of a single-phase transformer with a neat labelled diagram.

Q.5 (b) Draw the construction of a DC Motor and label its parts. What are the types of DC Motor?

Q.5 (c) Find supply current, current in each branch and total power factor.

[Circuit (dark photograph; values partly illegible in the source scan): an AC source marked "~" at the bottom, labelled approximately "230 V, 50 Hz" (first digits unclear), feeds two parallel branches. Upper branch: a resistor (read as 10 Ω) in series with an inductor (read as 0.12 H). Lower branch: a resistor (read as 10 Ω) in series with a capacitor (read as 60 μF).]

Q.6 (a) Determine Norton's equivalent circuit which may be used to represent the given network at the terminals AB and hence find current through 5 Ω resistance.

[Circuit: a common bottom wire ending at terminal B. Left branch: a 12 V source (circle, + at the top) in series with a 2 Ω resistor above it, connected from the bottom wire up to the top-left node N. From N a 6 Ω resistor goes down to the bottom wire (middle branch). From N a 4 Ω resistor in the top wire goes to terminal A. A 5 Ω resistor is connected between A and B (right side).]

Q.6 (b) Define the following terms in the series RLC resonance circuit (i) Resonance Frequency, (ii) Resonance curve, (iii) Half-power frequencies or Cut-off frequencies, (iv) Bandwidth, (v) Quality factor

Q.6 (c) Compare BJT and FET