Electrical Engineering questions for GATE, PSU recruitment and SSC JE draw from network theory, electrical machines, power systems, control systems, measurements and instrumentation, analog and digital electronics, and electromagnetic fields. Numerical answers include the formula used and the unit at each stage, which is where marks are commonly lost even when the approach is correct.
The Thevenin equivalent resistance (Rth) is found by:
Answer: D
Rth is calculated by deactivating all independent sources (short voltage sources, open current sources) and finding equivalent resistance seen from load terminals.
Q.62Easy
In a bridge circuit at balance condition, the product of opposite resistances are equal. This principle is known as:
Answer: C
At Wheatstone bridge balance: R₁/R₂ = R₄/R₃ or R₁×R₃ = R₂×R₄. No current flows through galvanometer.
Q.63Medium
A network has 8 branches and 5 nodes. The number of independent mesh equations required is:
Answer: B
Number of independent mesh equations = b - n + 1, where b=branches, n=nodes. Here: 8 - 5 + 1 = 4
Q.64Medium
For maximum power transfer to a load from a source with Thevenin equivalent (Vth, Rth), the load resistance should be:
Answer: C
Maximum power transfer theorem: Load resistance RL should equal Thevenin resistance Rth for maximum power delivery. Maximum power = Vth²/(4Rth)
Q.65Medium
In a planar circuit, the relationship between number of nodes (n), branches (b), and independent loops (m) is:
Answer: B
For a connected planar circuit: Number of independent loops = b - n + 1 (also known as cyclomatic complexity or mesh rank)
Q.66Easy
A circuit has three meshes. Using mesh current analysis, the total number of mesh current variables are:
Answer: B
Number of mesh current variables equals the number of independent meshes in the circuit. For 3 independent meshes, we have 3 mesh currents (I₁, I₂, I₃).
Q.67Medium
The reciprocity theorem states that in a linear bilateral network:
Answer: C
Reciprocity theorem: If a voltage source at port 1 produces current at port 2, then the same source at port 2 produces equal current at port 1. Applicable for bilateral linear networks.
Q.68Medium
In a circuit, the star-delta transformation is used to:
Answer: D
Star-delta transformation converts between two three-terminal network configurations, simplifying circuit analysis by eliminating nodes that cannot be solved directly.
Q.69Hard
For a passive linear network, the input impedance looking into terminals is Z(s). If a unit impulse is applied as input, the impulse response h(t) is the:
Answer: C
Impulse response h(t) = L⁻¹[Y(s)] where Y(s) is admittance. For impedance Z(s), admittance Y(s) = 1/Z(s).
Q.70Medium
In mesh analysis, if a circuit has dependent sources, the approach is:
Answer: B
Mesh analysis works with dependent sources by expressing the controlling variable in terms of mesh currents, then solving the resulting equations.
Q.71Medium
The Norton equivalent of a network is found by:
Answer: C
Norton equivalent: IN = Isc (short-circuit current) and RN = Rth (equivalent resistance). Norton and Thevenin equivalents are related: Vth = IN × RN
Q.72Hard
For a two-port network, when port 2 is open-circuited (I₂=0), the parameter measured is:
Answer: A
In hybrid (h) parameters: h₁₁ is input impedance with output open (I₂=0). h₁₁ = V₁/I₁|I₂=₀ measured in ohms.
Q.73Medium
In a circuit with mutual inductance between two coils, the coupling coefficient k is defined as:
Answer: B
Coupling coefficient k = M/√(L₁L₂), where 0 ≤ k ≤ 1. k=1 indicates perfect coupling, k=0 means no coupling.
Q.74Hard
The cut-set matrix is used in circuit analysis to:
Answer: B
Cut-set matrix provides a systematic way to write KVL equations for fundamental cut-sets, an alternative to mesh analysis.
Q.75Easy
A circuit element is said to be active if it:
Answer: B
Active elements (voltage/current sources) can supply power. Passive elements (R, L, C) can only dissipate or store energy.
Q.76Easy
For a network containing resistances and a single voltage source, if we open-circuit the source terminal, the circuit becomes:
Answer: B
Removing all independent sources leaves only passive elements (resistors), making the network passive with no energy supply capability.
Q.77Medium
In a magnetically coupled circuit with two inductors L₁ and L₂ with mutual inductance M, if current increases in primary, the induced voltage in secondary opposes this change. This demonstrates:
Answer: C
Faraday's law describes EMF generation; Lenz's law describes the direction (opposition to change). Both apply to mutual inductance phenomena.
Q.78Medium
A network is said to be bilateral if:
Answer: B
Bilateral networks are linear networks where reciprocal relationships hold. Networks with ideal diodes are unilateral (non-bilateral).
Q.79Easy
In nodal analysis, the number of independent equations required to solve a circuit with 'n' nodes (excluding the reference node) is:
Answer: A
In nodal analysis, we need (n-1) independent KCL equations for n nodes, where one node is taken as reference (ground). This follows from the fact that one equation is dependent on others.
Q.80Easy
A voltage source of 10V with internal resistance 2Ω is connected to a load resistance of 8Ω. The maximum power transfer to the load occurs when load resistance is:
Answer: A
Maximum power transfer theorem states that maximum power is transferred when load resistance equals the Thevenin equivalent resistance of the source (2Ω in this case).
