AC Fundamentals and Phasors
Q. What is the Norton equivalent current in a circuit?
A.
The short-circuit current at the terminals
B.
The open-circuit voltage
C.
The total current in the circuit
D.
The current through the load
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Solution
The Norton equivalent current is defined as the current that flows through a short circuit placed across the terminals of the circuit.
Correct Answer: A — The short-circuit current at the terminals
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Q. What is the Norton equivalent of a circuit?
A.
A single voltage source and series resistance
B.
A single current source and parallel resistance
C.
A combination of inductors
D.
A complex impedance
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Solution
The Norton equivalent circuit is represented by a single current source in parallel with a resistance, simplifying the analysis of the circuit.
Correct Answer: B — A single current source and parallel resistance
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Q. What is the phase difference between voltage and current in a purely capacitive AC circuit?
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
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Solution
In a purely capacitive circuit, the current leads the voltage by 90 degrees.
Correct Answer: B — 90 degrees
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Q. What is the phase difference between voltage and current in a purely resistive AC circuit?
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
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Solution
In a purely resistive AC circuit, the voltage and current are in phase, meaning the phase difference is 0 degrees.
Correct Answer: A — 0 degrees
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Q. What is the power consumed by a resistor of 10Ω when a current of 2A flows through it?
A.
20W
B.
40W
C.
10W
D.
5W
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Solution
Power (P) can be calculated using P = I^2 * R. Therefore, P = (2A)^2 * 10Ω = 4 * 10 = 40W.
Correct Answer: A — 20W
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Q. What is the power factor in an AC circuit with a resistive load?
A.
1
B.
0
C.
0.5
D.
0.707
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Solution
The power factor in an AC circuit with a purely resistive load is 1, indicating that all the power is being used effectively.
Correct Answer: A — 1
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Q. What is the power factor of a purely resistive AC circuit?
A.
0
B.
0.5
C.
1
D.
Infinity
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Solution
The power factor is defined as the cosine of the phase angle between voltage and current. In a purely resistive circuit, this angle is 0 degrees, so the power factor is 1.
Correct Answer: C — 1
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Q. What is the relationship defined by Ohm's Law?
A.
V = I * R
B.
P = V * I
C.
Z = V / I
D.
I = V / R
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Solution
Ohm's Law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with the resistance (R) being the constant of proportionality.
Correct Answer: A — V = I * R
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Q. What is the Thevenin equivalent of a circuit?
A.
A single voltage source and series resistance
B.
A single current source and parallel resistance
C.
A combination of capacitors
D.
A complex impedance
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Solution
The Thevenin equivalent circuit is represented by a single voltage source in series with a resistance, simplifying the analysis of the circuit.
Correct Answer: A — A single voltage source and series resistance
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Q. What is the Thevenin equivalent voltage (Vth) across terminals A and B if V1 = 10V and R1 = 5Ω, R2 = 10Ω in series?
A.
10V
B.
5V
C.
15V
D.
0V
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Solution
In a series circuit, the Thevenin voltage is the same as the source voltage, so Vth = V1 = 10V.
Correct Answer: A — 10V
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Q. What is the Thevenin equivalent voltage if a circuit has a 10V source and a 2Ω resistor in series with a 4Ω load?
A.
2.5V
B.
4V
C.
10V
D.
12V
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Solution
The Thevenin equivalent voltage is the open-circuit voltage across the load, which is the same as the source voltage in this case, 10V.
Correct Answer: C — 10V
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Q. What is the Thevenin equivalent voltage in a circuit?
A.
The open-circuit voltage at the terminals
B.
The short-circuit current
C.
The total voltage in the circuit
D.
The voltage drop across the load
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Solution
The Thevenin equivalent voltage is defined as the open-circuit voltage measured across the terminals of the circuit.
Correct Answer: A — The open-circuit voltage at the terminals
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Q. What is the unit of impedance?
A.
Ohm
B.
Volt
C.
Ampere
D.
Watt
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Solution
The unit of impedance is the Ohm (Ω), which measures the opposition that a circuit presents to the flow of alternating current.
Correct Answer: A — Ohm
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