1Which of the following expressions correctly represents the relationship between current (), charge (), and time ()?
A.
B.
C.
D.
Correct Answer:
Explanation:
Electric current is defined as the rate of flow of charge with respect to time. Therefore, the instantaneous current is given by the derivative of charge with respect to time, .
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2The energy stored in an inductor of inductance carrying a current is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
The energy stored in the magnetic field of an inductor is calculated using the formula , where is in Henrys and is in Amperes.
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3Which of the following statements regarding Ohm's Law is false?
A.It is applicable to non-linear devices like diodes and Zener diodes.
B.It states that potential difference is directly proportional to current, provided temperature remains constant.
C.The ratio represents resistance.
D.It is applicable to linear bilateral elements.
Correct Answer: It is applicable to non-linear devices like diodes and Zener diodes.
Explanation:
Ohm's Law applies strictly to linear conductors where resistance is constant. Non-linear devices like diodes do not have a constant resistance and do not follow the linear relationship.
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4Kirchhoff’s Current Law (KCL) is a consequence of the law of conservation of:
A.Charge
B.Momentum
C.Flux
D.Energy
Correct Answer: Charge
Explanation:
KCL states that the algebraic sum of currents entering a node is zero. This implies that charge cannot accumulate at a node, reflecting the law of conservation of charge.
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5Kirchhoff’s Voltage Law (KVL) states that the algebraic sum of voltages around a closed path is zero. This is based on the conservation of:
A.Current
B.Power
C.Charge
D.Energy
Correct Answer: Energy
Explanation:
KVL implies that the total energy gained per unit charge is equal to the total energy lost per unit charge around a closed loop, which is a statement of the conservation of energy.
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6Two resistors and are connected in parallel. What is the equivalent resistance ?
A.
B.
C.
D.
Correct Answer:
Explanation:
For two resistors in parallel, the reciprocal of the equivalent resistance is the sum of the reciprocals of the individual resistances: . Solving for gives .
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7According to the Voltage Division Rule, the voltage drop across a resistor in a series circuit with , , and a total voltage source is:
A.
B.
C.
D.
Correct Answer:
Explanation:
In a series circuit, voltage is divided proportionally to the resistance. Therefore, the voltage across is the total voltage times the ratio of to the total resistance ().
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8Using the Current Division Rule for two parallel resistors and with a total entering current , the current flowing through is:
A.
B.
C.
D.
Correct Answer:
Explanation:
Current in parallel branches divides inversely to the resistance. The current through depends on the resistance of the other branch, . Thus, .
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9What is the internal resistance of an ideal voltage source?
A.Dependent on the load
B.Infinite
C.Zero
D.Very high
Correct Answer: Zero
Explanation:
An ideal voltage source maintains a constant terminal voltage regardless of the current drawn. This implies there is no internal voltage drop, which corresponds to zero internal resistance.
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10What is the internal resistance of an ideal current source?
A.Negative
B.Zero
C.Infinite
D.1 Ohm
Correct Answer: Infinite
Explanation:
An ideal current source delivers a constant current regardless of the voltage across its terminals. For the current to remain constant despite external load changes, the internal parallel resistance must be infinite.
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11In a Star (Y) to Delta () transformation, if are the star-connected resistors connected to a neutral point, the equivalent Delta resistor between terminals A and B is:
A.
B.
C.
D.
Correct Answer:
Explanation:
The formula for converting Star resistors to a Delta resistor between two specific nodes is the sum of the two connected Star resistors plus their product divided by the third (opposite) Star resistor.
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12Three equal resistors of value are connected in a Delta () configuration. What is the value of each resistor in the equivalent Star (Y) configuration?
A.
B.
C.
D.
Correct Answer:
Explanation:
When converting from Delta to Star with identical resistors, the resistance decreases by a factor of 3. Thus, .
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13Mesh analysis is primarily based on the application of:
A.Maximum Power Transfer Theorem
B.Current Division Rule
C.Kirchhoff’s Voltage Law (KVL)
D.Kirchhoff’s Current Law (KCL)
Correct Answer: Kirchhoff’s Voltage Law (KVL)
Explanation:
Mesh analysis involves defining mesh currents and writing equations for the sum of voltages around each closed mesh, which is an application of KVL.
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14Nodal analysis is primarily based on the application of:
A.Superposition Theorem
B.Kirchhoff’s Voltage Law (KVL)
C.Voltage Division Rule
D.Kirchhoff’s Current Law (KCL)
Correct Answer: Kirchhoff’s Current Law (KCL)
Explanation:
Nodal analysis involves defining node voltages and writing equations for the sum of currents leaving or entering a node, which is an application of KCL.
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15A dependent source represented by a diamond shape with a +/- sign inside, controlled by a current elsewhere in the circuit, is known as a:
A.Voltage Controlled Current Source (VCCS)
B.Current Controlled Voltage Source (CCVS)
C.Voltage Controlled Voltage Source (VCVS)
D.Current Controlled Current Source (CCCS)
Correct Answer: Current Controlled Voltage Source (CCVS)
Explanation:
The +/- sign indicates it is a Voltage Source. Since it is controlled by a current () elsewhere, it is a Current Controlled Voltage Source (CCVS). Its value is typically given as .
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16The Superposition Theorem is valid only for:
A.Networks with only one source
B.Non-linear networks
C.Unilateral networks
D.Linear networks
Correct Answer: Linear networks
Explanation:
Superposition relies on the property of linearity (additivity and homogeneity). It cannot be applied to non-linear circuits (e.g., those containing diodes or calculating power directly).
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17When applying the Superposition Theorem, how should ideal voltage sources be treated when they are 'turned off'?
A.Replaced by their internal resistance (infinity)
B.Left as is
C.Open circuited
D.Short circuited
Correct Answer: Short circuited
Explanation:
To turn off a voltage source (make ), the potential difference must be zero, which is achieved by a short circuit.
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18When applying the Superposition Theorem, how should ideal current sources be treated when they are 'turned off'?
A.Short circuited
B.Replaced by a wire
C.Grounded
D.Open circuited
Correct Answer: Open circuited
Explanation:
To turn off a current source (make ), the path must be broken to stop flow, which is achieved by an open circuit.
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19Thevenin’s Theorem states that any linear two-terminal circuit can be replaced by:
A.A single current source in parallel with a resistor
B.A single voltage source in parallel with a resistor
C.A single current source in series with a resistor
D.A single voltage source in series with a resistor
Correct Answer: A single voltage source in series with a resistor
Explanation:
Thevenin’s Theorem simplifies a complex linear network into an equivalent circuit consisting of a single voltage source () connected in series with an equivalent resistance ().
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20Norton’s Theorem states that any linear two-terminal circuit can be replaced by:
A.A single current source in parallel with a resistor
B.A single current source in series with a resistor
C.A single voltage source in parallel with a resistor
D.A single voltage source in series with a resistor
Correct Answer: A single current source in parallel with a resistor
Explanation:
Norton’s Theorem simplifies a network into an equivalent circuit consisting of a current source () connected in parallel with an equivalent resistance ().
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21How are Thevenin resistance () and Norton resistance () related for the same network terminals?
A.
B.
C.
D.
Correct Answer:
Explanation:
The resistance looking into the terminals is calculated the same way for both theorems (turning off independent sources). Therefore, the numeric value of the Thevenin resistance is equal to the Norton resistance.
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22To calculate the Thevenin voltage () across terminals A and B, you must find:
A.The power dissipated between A and B
B.The open-circuit voltage across A and B
C.The resistance between A and B with sources active
D.The short-circuit current between A and B
Correct Answer: The open-circuit voltage across A and B
Explanation:
The Thevenin voltage is defined as the voltage appearing across the load terminals when the load is removed (open circuit).
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23To calculate the Norton current () between terminals A and B, you must find:
A.The open-circuit voltage across A and B
B.The current flowing when A and B are open
C.The short-circuit current flowing between A and B
D.The voltage when A and B are shorted
Correct Answer: The short-circuit current flowing between A and B
Explanation:
The Norton current is defined as the current that flows through the terminals when they are shorted together.
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24The Maximum Power Transfer Theorem states that maximum power is transferred to the load resistance from a source with internal resistance when:
A.
B.
C.
D.
Correct Answer:
Explanation:
For DC circuits, maximum power is transferred from the source to the load when the load resistance equals the source (Thevenin equivalent) resistance.
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25What is the efficiency of power transfer at the condition of Maximum Power Transfer?
A.25%
B.50%
C.100%
D.75%
Correct Answer: 50%
Explanation:
At maximum power transfer, . The total resistance is . Half the voltage drops across the source resistance and half across the load. Thus, half the power is dissipated internally and half is delivered to the load, resulting in 50% efficiency.
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26If a Thevenin equivalent circuit has and , what is the value of the maximum power that can be delivered to a load?
A.10 W
B.20 W
C.5 W
D.50 W
Correct Answer: 5 W
Explanation:
The formula for maximum power is . Substituting the values: .
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27What is the SI unit of conductance?
A.Volt (V)
B.Henry (H)
C.Ohm ()
D.Siemens (S)
Correct Answer: Siemens (S)
Explanation:
Conductance is the reciprocal of resistance. Its unit is Siemens (S), formerly known as Mho ().
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28Power consumed by a resistor is given by which of the following formulas?
A.All of the above
B.
C.
D.
Correct Answer: All of the above
Explanation:
Using Ohm's Law (), power can be written as or . All three are valid.
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29In a series circuit containing , , and , what is the total resistance?
A.
B.
C.
D.
Correct Answer:
Explanation:
For resistors in series, resistances add up: .
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30If a 10V source is connected across two resistors in parallel, what is the total current drawn from the source?
A.4 A
B.1 A
C.2 A
D.0.5 A
Correct Answer: 4 A
Explanation:
First, find for two in parallel: . Then .
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31Which of the following is considered a 'bilateral' element?
A.Diode
B.Battery
C.Resistor
D.Transistor
Correct Answer: Resistor
Explanation:
A bilateral element conducts current equally well in both directions and offers the same impedance. A resistor is bilateral, whereas a diode is unilateral.
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32What happens to the resistance of a metallic conductor when its temperature increases?
A.It increases
B.It becomes zero
C.It decreases
D.It remains constant
Correct Answer: It increases
Explanation:
Metals have a positive temperature coefficient of resistance. As temperature rises, lattice vibrations increase, impeding electron flow, thus increasing resistance.
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33In a node with 3 branches, if 2A enters, 3A enters, and current leaves, what is the value of ?
A.5 A
B.-1 A
C.6 A
D.1 A
Correct Answer: 5 A
Explanation:
According to KCL, sum of entering currents = sum of leaving currents. . Therefore, .
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34A 'Supernode' is formed in Nodal analysis when:
A.A current source is between two non-reference nodes
B.A resistor is in parallel with a voltage source
C.A voltage source is connected between two non-reference nodes
D.A voltage source is connected between a non-reference node and the ground
Correct Answer: A voltage source is connected between two non-reference nodes
Explanation:
When an ideal voltage source is located between two nodes neither of which is the reference (ground), the current through the source is unknown, forming a Supernode requiring a combined KCL equation.
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35If the voltage across a capacitor increases from 0V to 10V, the energy stored is:
A.20 J
B.200 J
C.10 J
D.100 J
Correct Answer: 100 J
Explanation:
Energy in a capacitor is . Here .
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36The property of a circuit element to oppose the change in current flowing through it is called:
A.Capacitance
B.Conductance
C.Resistance
D.Inductance
Correct Answer: Inductance
Explanation:
Inductance is the property where an electromotive force is induced to oppose any change in current ().
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37In Source Transformation, a voltage source in series with resistance can be converted into:
A.A current source in parallel with
B.A current source in series with
C.A current source in series with
D.A current source in parallel with
Correct Answer: A current source in parallel with
Explanation:
Source transformation allows converting a practical voltage source (V series R) into a practical current source (I parallel R), where .
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38If three resistors are connected in Delta, the equivalent Star resistance for each leg is:
A.
B.
C.
D.
Correct Answer:
Explanation:
For equal resistors, . .
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39A , lamp has a resistance of:
A.
B.
C.
D.
Correct Answer:
Explanation:
Using , we get . .
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40Which theorem is useful for analyzing a circuit when the load resistance varies, but the rest of the circuit remains constant?
A.Thevenin’s Theorem
B.Superposition Theorem
C.Mesh Analysis
D.KCL
Correct Answer: Thevenin’s Theorem
Explanation:
Thevenin's theorem is particularly useful here because it reduces the fixed part of the circuit to a simple and , making it easy to recalculate current/voltage for different values of .
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41If a circuit has nodes and branches, the number of independent KCL equations (nodal equations) required is:
A.
B.
C.
D.
Correct Answer:
Explanation:
In Nodal analysis, we choose one reference node. Equations are written for the remaining non-reference nodes, so we need equations.
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42If a circuit has nodes and branches, the number of independent KVL equations (mesh equations) required is:
A.
B.
C.
D.
Correct Answer:
Explanation:
The number of independent loops (meshes) in a planar network is given by the fundamental topology equation .
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43A specific resistor in a circuit dissipates power when voltage source acts alone, and dissipates power when voltage source acts alone. Can we calculate total power as using Superposition?
A.No, superposition does not apply to power.
B.Yes, if the sources are DC.
C.Yes, superposition applies to power.
D.Yes, if the resistors are linear.
Correct Answer: No, superposition does not apply to power.
Explanation:
Superposition applies to voltage and current (linear quantities). Power is a quadratic quantity ( or ). The total power is not the sum of individual powers; you must sum the currents/voltages first, then calculate power.
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44For a short circuit, the resistance and voltage are theoretically:
A.
B.
C.
D.
Correct Answer:
Explanation:
A short circuit implies a zero-resistance path (). According to Ohm's law, voltage drop across zero resistance is zero (), although current can be non-zero.
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45For an open circuit, the resistance and current are theoretically:
A.
B.
C.
D.
Correct Answer:
Explanation:
An open circuit implies a break in the path, corresponding to infinite resistance (). Consequently, no current can flow ().
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46Which of the following is an active element?
A.Capacitor
B.Inductor
C.Resistor
D.Voltage Source
Correct Answer: Voltage Source
Explanation:
Active elements can generate or amplify energy (e.g., Voltage Source, Current Source, Transistor). Passive elements (R, L, C) consume or store energy but cannot generate it.
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47The time rate of change of work is defined as:
A.Voltage
B.Power
C.Force
D.Energy
Correct Answer: Power
Explanation:
Power is defined as the rate at which work is done or energy is transferred. .
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48In a series circuit, which quantity remains the same across all elements?
A.None of the above
B.Voltage
C.Power
D.Current
Correct Answer: Current
Explanation:
In a series circuit, there is only one path for electron flow, so the current is the same through every component.
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49In a parallel circuit, which quantity remains the same across all parallel branches?
A.Power
B.Voltage
C.Resistance
D.Current
Correct Answer: Voltage
Explanation:
In a parallel circuit, all components are connected between the same two nodes, so the potential difference (voltage) across them is identical.
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50If a current of 2A flows through a resistor for 10 seconds, the charge transferred is: