1.1 Thevenin's theorem states that any linear circuit with multiple voltage and current sources can be replaced by:
Correct Answer: b) A voltage source in series with a resistor
Explanation: Thevenin's Theorem states that any linear bilateral network with voltage and current sources and resistances can be replaced by an equivalent circuit consisting of a single voltage source (VTH) in series with a single resistance (RTH). This simplifies complex networks for analysis.
1.2 In Thevenin's theorem, the Thevenin resistance is found by:
Correct Answer: b) Replacing all sources with short circuits
Explanation: To find Thevenin resistance (RTH): 1. Replace all voltage sources with short circuits (zero resistance) 2. Replace all current sources with open circuits (infinite resistance) 3. Calculate the equivalent resistance between the terminals This gives the resistance "seen" from the open terminals.
1.3 The Thevenin voltage is:
Correct Answer: a) The voltage measured across the open terminals
Explanation: The Thevenin voltage (VTH) is the open-circuit voltage measured at the terminals of interest when the load is removed. It represents the voltage that would appear across the output terminals if no current were being drawn from them.
1.4 Thevenin's theorem is valid for:
Correct Answer: c) Both DC and AC circuits
Explanation: Thevenin's theorem applies to both DC and AC linear circuits. For AC circuits, the Thevenin equivalent consists of a voltage source and a complex impedance (instead of just resistance). The theorem doesn't apply to nonlinear circuits.
1.5 To find the Thevenin equivalent circuit, the load resistor is:
Correct Answer: b) Open-circuited
Explanation: When finding the Thevenin equivalent, the load resistor must be removed (open-circuited) to: 1. Calculate the open-circuit voltage (VTH) 2. Determine the equivalent resistance (RTH) looking back into the circuit The load is only reconnected after the Thevenin equivalent has been determined.
2.1 Norton's theorem states that any linear circuit with multiple sources can be replaced by:
Correct Answer: b) A current source in parallel with a resistor
Explanation: Norton's Theorem is the dual of Thevenin's Theorem. It states that any linear bilateral network can be replaced by an equivalent circuit consisting of a single current source (IN) in parallel with a single resistance (RN). This is useful for analyzing circuits with parallel connections.
2.2 The Norton current is found by:
Correct Answer: b) Short-circuiting the terminals
Explanation: The Norton current (IN) is the current that would flow through a short circuit placed across the output terminals. To measure it: 1. Remove the load resistor 2. Short-circuit the terminals 3. Measure the current through this short This is the maximum current the network can deliver.
2.3 Norton's resistance is the same as:
Correct Answer: a) The Thevenin resistance
Explanation: Norton resistance (RN) is identical to Thevenin resistance (RTH). Both represent the equivalent resistance of the network looking back from the terminals with all independent sources turned off (voltage sources shorted, current sources opened).
2.4 The Norton equivalent circuit consists of:
Correct Answer: b) A current source and a parallel resistor
Explanation: The Norton equivalent circuit has two components: 1. A current source (IN) representing the short-circuit current 2. A parallel resistor (RN) representing the equivalent resistance This is the current-source version of the Thevenin equivalent (voltage source with series resistance).
2.5 Thevenin's and Norton's theorems are:
Correct Answer: c) Interchangeable representations of the same circuit
Explanation: Thevenin and Norton equivalents are dual representations of the same linear network and can be converted between each other using: VTH = IN × RN RTH = RN Both are valid for linear circuits (DC or AC) and provide equivalent representations that can be chosen based on which is more convenient for analysis.
3.1 An alternating current (AC) waveform is:
Correct Answer: b) A sinusoidal voltage source that varies periodically
Explanation: Alternating Current (AC) is characterized by a sinusoidal waveform that periodically reverses direction. The standard AC waveform follows the mathematical function: v(t) = Vpsin(ωt + φ), where Vp is peak voltage, ω is angular frequency, and φ is phase angle.
3.2 The time period of an AC signal is:
Correct Answer: d) Both (a) and (b)
Explanation: The time period (T) of an AC waveform is: 1. The duration of one complete cycle (from peak to peak, or zero crossing to zero crossing) 2. Mathematically related to frequency (f) by T = 1/f For example, 60Hz AC has T = 1/60 ≈ 16.67ms per cycle.
3.3 In an AC circuit, power is given by:
Correct Answer: d) All of the above
Explanation: In AC circuits, power can be calculated using: 1. P = VI (using RMS values) 2. P = V²/R (when voltage and resistance are known) 3. P = I²R (when current and resistance are known) For purely resistive loads, these give the real power. For reactive loads, complex power calculations are needed.
3.4 A sine wave has a peak voltage of 100V. Its peak-to-peak voltage is:
Correct Answer: c) 200V
Explanation: Peak-to-peak voltage (Vpp) is the difference between maximum positive and maximum negative peaks: Vpp = 2 × Vpeak For Vpeak = 100V: Vpp = 2 × 100V = 200V RMS voltage would be Vrms = Vpeak/√2 ≈ 70.7V
3.5 The frequency of an AC waveform is measured in:
Correct Answer: c) Hertz
Explanation: Frequency (f) is measured in Hertz (Hz), which represents cycles per second. Other units: • Ohms (Ω) - measure of resistance • Watts (W) - measure of power • Coulombs (C) - measure of electric charge Common AC frequencies include 50Hz (Europe) and 60Hz (North America).