Q. According to Kirchhoff's Current Law (KCL), what can be said about the currents entering and leaving a junction?
A.They are always equal
B.They can be different
C.They depend on voltage
D.They are always zero
Solution
KCL states that the total current entering a junction must equal the total current leaving that junction.
Correct Answer: A — They are always equal
Q. According to Kirchhoff's Current Law (KCL), what must be true at a junction in an electrical circuit?
A.The sum of voltages is zero
B.The sum of currents entering equals the sum of currents leaving
C.Power is conserved
D.Resistance is constant
Solution
KCL states that the total current entering a junction must equal the total current leaving that junction.
Correct Answer: B — The sum of currents entering equals the sum of currents leaving
Q. According to Kirchhoff's Current Law (KCL), what must be true at any junction in an electrical circuit?
A.The sum of currents entering equals the sum of currents leaving
B.The voltage is constant
C.The total resistance is zero
D.Power is conserved
Solution
KCL states that the total current entering a junction must equal the total current leaving that junction.
Correct Answer: A — The sum of currents entering equals the sum of currents leaving
Q. How do you calculate the total power in a resistive AC circuit?
A.P = V^2 / R
B.P = I^2 * R
C.P = V * I * cos(φ)
D.P = R * I
Solution
In a resistive AC circuit, the total power (P) can be calculated using the formula P = V * I * cos(φ), where φ is the phase angle between voltage and current.
Correct Answer: C — P = V * I * cos(φ)
Q. How do you calculate the total power in a three-phase AC system?
A.P = √3 * V * I
B.P = V * I
C.P = 3 * V * I
D.P = V^2 / R
Solution
The total power in a balanced three-phase AC system can be calculated using the formula P = √3 * V * I, where V is the line voltage and I is the line current.
Correct Answer: A — P = √3 * V * I
Q. If a circuit has a Norton equivalent current of 3A and a Norton equivalent resistance of 4Ω, what is the equivalent voltage?
A.12V
B.7V
C.3V
D.1.5V
Solution
Using Ohm's Law, V = I * R = 3A * 4Ω = 12V.
Correct Answer: A — 12V
Q. If a circuit has a Norton equivalent current of 5A and a Norton equivalent resistance of 2Ω, what is the equivalent voltage?
A.2V
B.5V
C.10V
D.7V
Solution
Using Ohm's Law, V = I * R = 5A * 2Ω = 10V.
Correct Answer: C — 10V
Q. In a parallel AC circuit, how does the total current relate to the individual branch currents according to KCL?
A.Total current is the sum of branch currents
B.Total current is the average of branch currents
C.Total current is the maximum branch current
D.Total current is the minimum branch current
Solution
In a parallel AC circuit, the total current is the sum of the currents through each branch, as stated by Kirchhoff's Current Law (KCL).
Correct Answer: A — Total current is the sum of branch currents
Q. In a parallel circuit, what is the total current if the branch currents are 2A, 3A, and 5A?
A.10A
B.5A
C.3A
D.2A
Solution
In a parallel circuit, the total current is the sum of the branch currents: 2A + 3A + 5A = 10A.
Correct Answer: A — 10A
Q. In a series AC circuit, how does the total impedance (Z) relate to resistance (R) and reactance (X)?
A.Z = R + X
B.Z = R - X
C.Z = √(R^2 + X^2)
D.Z = R * X
Solution
The total impedance in a series AC circuit is calculated using the formula Z = √(R^2 + X^2), where R is resistance and X is reactance.
Correct Answer: C — Z = √(R^2 + X^2)
Q. In a series AC circuit, if the voltage is 120V and the current is 10A, what is the power consumed?
A.120W
B.100W
C.1000W
D.1200W
Solution
Power (P) in an AC circuit is calculated as P = V * I. Therefore, P = 120V * 10A = 1200W.
Correct Answer: D — 1200W
Q. In a series circuit, how does the total current relate to the individual branch currents according to KCL?
A.Total current is the sum of branch currents
B.Total current is the average of branch currents
C.Total current is the maximum branch current
D.Total current is the minimum branch current
Solution
According to Kirchhoff's Current Law (KCL), the total current entering a junction is equal to the total current leaving the junction, which means the total current is the sum of the branch currents.
Correct Answer: A — Total current is the sum of branch currents
Q. In a series circuit, if the total voltage is 12V and the resistance is 4Ω, what is the current flowing through the circuit?
A.3A
B.4A
C.12A
D.0.33A
Solution
Using Ohm's Law, I = V / R = 12V / 4Ω = 3A.
Correct Answer: A — 3A
Q. In a series RLC circuit, if the resistance is 10Ω, the inductance is 0.1H, and the capacitance is 100μF, what is the resonant frequency?
A.159.15Hz
B.100Hz
C.50Hz
D.200Hz
Solution
The resonant frequency (f0) is given by f0 = 1 / (2π√(LC)). Here, L = 0.1H and C = 100μF, so f0 = 1 / (2π√(0.1 * 0.0001)) = 159.15Hz.
Correct Answer: A — 159.15Hz
Q. In an AC circuit, what does the impedance (Z) represent?
A.Total opposition to current flow
B.Only resistance
C.Only reactance
D.Voltage drop
Solution
Impedance (Z) is the total opposition that a circuit offers to the flow of alternating current, combining both resistance and reactance.
Correct Answer: A — Total opposition to current flow
Q. In an AC circuit, what does the term 'impedance' refer to?
A.Resistance only
B.Total opposition to current
C.Voltage drop
D.Current flow
Solution
Impedance is the total opposition that a circuit offers to the flow of alternating current, which includes both resistance and reactance.
Correct Answer: B — Total opposition to current
Q. In an AC circuit, what is the phase difference between voltage and current in a purely resistive load?
A.0 degrees
B.90 degrees
C.180 degrees
D.270 degrees
Solution
In a purely resistive load, the voltage and current are in phase, meaning the phase difference is 0 degrees.
Correct Answer: A — 0 degrees
Q. In an AC circuit, what is the power factor?
A.Ratio of real power to apparent power
B.Ratio of reactive power to real power
C.Total power consumed
D.Voltage divided by current
Solution
The power factor in an AC circuit is defined as the ratio of real power (P) to apparent power (S), indicating how effectively the current is being converted into useful work.
Correct Answer: A — Ratio of real power to apparent power
Q. What does KCL state about currents at a junction?
A.The sum of currents entering equals the sum of currents leaving
B.The sum of voltages equals zero
C.Current is constant in a closed loop
D.Power is conserved in a circuit
Solution
Kirchhoff's Current Law (KCL) states that the total current entering a junction must equal the total current leaving that junction.
Correct Answer: A — The sum of currents entering equals the sum of currents leaving
Q. What does KVL (Kirchhoff's Voltage Law) state?
A.The sum of currents in a loop is zero
B.The sum of voltages in a closed loop is zero
C.The voltage across a resistor is constant
D.The total power in a circuit is zero
Solution
KVL states that the sum of the electrical potential differences (voltages) around any closed network is zero.
Correct Answer: B — The sum of voltages in a closed loop is zero
Q. What does KVL state about the voltages in a closed loop?
A.The sum of voltages is zero
B.The sum of currents is zero
C.The sum of resistances is zero
D.The sum of powers is zero
Solution
Kirchhoff's Voltage Law (KVL) states that the sum of the electrical potential differences (voltages) around any closed network is zero.
Correct Answer: A — The sum of voltages is zero
Q. What is the effect of increasing frequency on the reactance of a capacitor?
A.Reactance increases
B.Reactance decreases
C.Reactance remains constant
D.Reactance becomes zero
Solution
The reactance (Xc) of a capacitor decreases with increasing frequency, calculated as Xc = 1 / (2πfC), where f is the frequency and C is the capacitance.
Correct Answer: B — Reactance decreases
Q. What is the equivalent resistance of two resistors, R1 = 6Ω and R2 = 3Ω, in parallel?
A.2Ω
B.4Ω
C.9Ω
D.18Ω
Solution
The formula for equivalent resistance in parallel is 1/R_eq = 1/R1 + 1/R2. Thus, 1/R_eq = 1/6 + 1/3 = 1/2, so R_eq = 2Ω.
Correct Answer: B — 4Ω
Q. What is the formula for calculating power in an AC circuit?
A.P = V^2 / R
B.P = I^2 * R
C.P = V * I * cos(φ)
D.P = V / I
Solution
In an AC circuit, the real power (P) can be calculated using the formula P = V * I * cos(φ), where φ is the phase angle between the voltage and current.
Correct Answer: C — P = V * I * cos(φ)
Q. What is the formula for calculating the total power in a resistive AC circuit?
A.P = V^2 / R
B.P = I^2 * R
C.P = V * I * cos(φ)
D.P = R * I^2
Solution
In a resistive AC circuit, the total power (P) can be calculated using the formula P = V * I * cos(φ), where φ is the phase angle between the voltage and current.
Correct Answer: C — P = V * I * cos(φ)
Q. What is the formula for calculating the total power in a three-phase AC system?
A.P = √3 * V * I * cos(φ)
B.P = V * I
C.P = V^2 / R
D.P = I^2 * R
Solution
The total power in a three-phase AC system is calculated using the formula P = √3 * V * I * cos(φ), where φ is the phase angle.
Correct Answer: A — P = √3 * V * I * cos(φ)
Q. What is the formula for calculating total impedance in a series AC circuit?
A.Z = R + jX
B.Z = R - jX
C.Z = R * X
D.Z = R / X
Solution
In a series AC circuit, the total impedance (Z) is the sum of the resistance (R) and the reactance (X), expressed as Z = R + jX, where j is the imaginary unit.
Correct Answer: A — Z = R + jX
Q. What is the formula for calculating total impedance in a series RLC circuit?
A.Z = R + jX
B.Z = R + j(X_L - X_C)
C.Z = R + X_L + X_C
D.Z = R + j(X_C - X_L)
Solution
In a series RLC circuit, the total impedance (Z) is given by Z = R + j(X_L - X_C), where X_L is the inductive reactance and X_C is the capacitive reactance.
Correct Answer: B — Z = R + j(X_L - X_C)
Q. What is the impedance of a capacitor in an AC circuit at frequency f?
A.Z_C = 1 / (jωC)
B.Z_C = jωC
C.Z_C = R + jX_C
D.Z_C = R - jX_C
Solution
The impedance of a capacitor in an AC circuit is given by Z_C = 1 / (jωC), where ω = 2πf is the angular frequency.
Correct Answer: A — Z_C = 1 / (jωC)
Q. What is the impedance of a purely resistive circuit?
A.Z = R
B.Z = jX
C.Z = R + j0
D.Z = 0
Solution
In a purely resistive circuit, the impedance (Z) is equal to the resistance (R), as there is no reactance involved.
