Major Competitive Exams
Q. In a circuit with two inputs A and B, if A = 0 and B = 0, what is the output of an OR gate?
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Solution
An OR gate outputs 1 if at least one input is 1. Since both inputs are 0, the output is 0.
Correct Answer: A — 0
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Q. In a circuit with two loops, if the current in the first loop is 2 A and in the second loop is 3 A, what is the total current entering a junction where these loops meet?
A.
1 A
B.
5 A
C.
6 A
D.
2 A
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Solution
According to Kirchhoff's current law, the total current entering a junction equals the total current leaving it. Therefore, total current = 2 A + 3 A = 5 A.
Correct Answer: B — 5 A
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Q. In a circuit with two loops, if the current in the first loop is 5 A and the second loop is 3 A, what is the current through a shared resistor of 2 ohms?
A.
1 A
B.
2 A
C.
3 A
D.
5 A
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Solution
The current through the shared resistor is the difference of the currents in the loops, so 5 A - 3 A = 2 A.
Correct Answer: A — 1 A
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Q. In a circuit with two resistors in parallel, if one resistor is 4 ohms and the other is 6 ohms, what is the equivalent resistance?
A.
2.4 ohms
B.
10 ohms
C.
24 ohms
D.
3.6 ohms
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Solution
Using the formula for resistors in parallel, 1/R_eq = 1/4 + 1/6, we find R_eq = 2.4 ohms.
Correct Answer: A — 2.4 ohms
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Q. In a circuit with two resistors in parallel, if one resistor is 4Ω and the other is 12Ω, what is the total current flowing through the circuit when connected to a 24V battery?
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Solution
First, find the equivalent resistance: 1/R_eq = 1/4 + 1/12 = 1/3. R_eq = 3Ω. Then, I = V/R = 24V / 3Ω = 8A.
Correct Answer: D — 6A
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Q. In a circuit with two resistors in parallel, if one resistor is 6Ω and the other is 3Ω, what is the total current flowing if the voltage across the parallel combination is 12V?
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Solution
Total current I = V / Req; Req = 1/(1/6 + 1/3) = 2Ω; I = 12V / 2Ω = 6A.
Correct Answer: B — 4A
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Q. In a circuit with two resistors in parallel, if one resistor is 6Ω and the other is 3Ω, what is the total current if a voltage of 12V is applied across the combination?
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Solution
Total resistance in parallel: 1/Rtotal = 1/6 + 1/3 = 1/2. Rtotal = 2Ω. Total current I = V/R = 12V/2Ω = 6A.
Correct Answer: B — 4A
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Q. In a circuit with two resistors in parallel, if one resistor is 6Ω and the other is 3Ω, what is the total current flowing if the voltage across the circuit is 12V?
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Solution
Total resistance in parallel: 1/Rtotal = 1/6 + 1/3 = 1/2. Rtotal = 2Ω. Total current I = V/R = 12V/2Ω = 6A.
Correct Answer: B — 4A
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Q. In a circuit with two resistors in parallel, if one resistor is 6Ω and the other is 3Ω, what is the total current flowing through the circuit when connected to a 12V battery?
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Solution
First, find the equivalent resistance: 1/R_eq = 1/6 + 1/3 = 1/2, R_eq = 2Ω. Then, I = V/R = 12V/2Ω = 6A.
Correct Answer: B — 4A
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Q. In a circuit with two resistors in series, if R1 = 4Ω and R2 = 6Ω, what is the total resistance?
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Solution
The total resistance in series is R_total = R1 + R2 = 4Ω + 6Ω = 10Ω.
Correct Answer: D — 10Ω
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Q. In a circuit with two resistors in series, if the total resistance is 12 ohms and one resistor is 4 ohms, what is the value of the other resistor?
A.
8 ohms
B.
4 ohms
C.
12 ohms
D.
16 ohms
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Solution
Using the formula for resistors in series, R_total = R1 + R2, we have 12 = 4 + R2, thus R2 = 12 - 4 = 8 ohms.
Correct Answer: A — 8 ohms
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Q. In a circuit with two resistors in series, if the total voltage across the circuit is 12V and the resistors are 4Ω and 6Ω, what is the voltage across the 4Ω resistor?
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Solution
Using the voltage divider rule, V1 = (R1 / (R1 + R2)) * Vtotal = (4 / (4 + 6)) * 12 = 4.8V.
Correct Answer: A — 4V
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Q. In a circuit with two resistors in series, if the total voltage across the circuit is 12V and the resistors have values of 4Ω and 6Ω, what is the voltage across the 4Ω resistor?
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Solution
Using the voltage divider rule, V1 = (R1 / (R1 + R2)) * Vtotal = (4 / (4 + 6)) * 12 = 4.8V.
Correct Answer: B — 6V
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Q. In a circuit, a capacitor is charged and then discharged through a resistor. What is the time constant of the circuit?
A.
RC
B.
C/R
C.
R/C
D.
1/RC
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Solution
The time constant (τ) of an RC circuit is given by τ = R * C.
Correct Answer: A — RC
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Q. In a circuit, if a capacitor is fully charged, what is the voltage across it?
A.
Zero
B.
Equal to the source voltage
C.
Half of the source voltage
D.
Double the source voltage
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Solution
When a capacitor is fully charged, the voltage across it is equal to the voltage of the source it was connected to.
Correct Answer: B — Equal to the source voltage
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Q. In a circuit, if the current is doubled while the resistance remains constant, what happens to the power consumed? (2020)
A.
It doubles
B.
It triples
C.
It remains the same
D.
It halves
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Solution
Power is given by P = I²R. If I is doubled, P becomes (2I)²R = 4I²R, which means power quadruples.
Correct Answer: A — It doubles
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Q. In a circuit, if the resistance is doubled while the voltage remains constant, what happens to the current? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, I = V/R. If R is doubled, I will be halved.
Correct Answer: B — It halves
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Q. In a circuit, if the resistance is halved while the voltage remains constant, what happens to the current? (2022)
A.
It halves
B.
It doubles
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, I = V/R. If R is halved, I will double.
Correct Answer: B — It doubles
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Q. In a circuit, if the voltage across a resistor is 12V and the current through it is 3A, what is the resistance?
A.
4 ohms
B.
3 ohms
C.
2 ohms
D.
1 ohm
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Solution
Using Ohm's law, R = V/I = 12V / 3A = 4 ohms.
Correct Answer: A — 4 ohms
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Q. In a circuit, if the voltage across a resistor is doubled, what happens to the current through it?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
According to Ohm's law, if voltage is doubled and resistance remains constant, current also doubles.
Correct Answer: A — Doubles
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Q. In a circuit, if the voltage is halved and the resistance remains constant, what happens to the current?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, if voltage is halved while resistance remains constant, current also halves.
Correct Answer: B — It halves
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Q. In a circuit, if the voltage is increased from 5V to 15V while the resistance remains constant at 5 ohms, what is the change in current?
A.
Increases by 1 A
B.
Increases by 2 A
C.
Increases by 3 A
D.
Increases by 4 A
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Solution
Initial current I1 = 5V / 5Ω = 1 A; Final current I2 = 15V / 5Ω = 3 A; Change in current = I2 - I1 = 3 A - 1 A = 2 A.
Correct Answer: C — Increases by 3 A
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Q. In a circuit, if the voltage is increased while keeping the resistance constant, what happens to the current?
A.
It decreases
B.
It increases
C.
It remains constant
D.
It becomes zero
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Solution
According to Ohm's Law, if voltage increases and resistance remains constant, the current will increase.
Correct Answer: B — It increases
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Q. In a circuit, if the voltage is increased while the resistance remains constant, what happens to the current?
A.
It decreases
B.
It increases
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's Law, if the voltage (V) increases and resistance (R) remains constant, the current (I) increases.
Correct Answer: B — It increases
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Q. In a circuit, two capacitors of capacitance 2μF and 3μF are connected in parallel. What is the total capacitance?
A.
5μF
B.
6μF
C.
1.2μF
D.
0.6μF
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Solution
The total capacitance C_total in parallel is the sum of individual capacitances: C_total = C1 + C2 = 2μF + 3μF = 5μF.
Correct Answer: A — 5μF
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Q. In a circuit, two capacitors of capacitance 3μF and 6μF are connected in parallel. What is the total capacitance?
A.
9μF
B.
2μF
C.
18μF
D.
1μF
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Solution
In parallel, the total capacitance is the sum: C_total = C1 + C2 = 3μF + 6μF = 9μF.
Correct Answer: A — 9μF
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Q. In a circuit, two capacitors of capacitance 4μF and 6μF are connected in parallel. What is the total capacitance?
A.
10μF
B.
24μF
C.
2.4μF
D.
0.4μF
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Solution
For capacitors in parallel, the total capacitance is the sum of the individual capacitances: C_total = C1 + C2 = 4μF + 6μF = 10μF.
Correct Answer: A — 10μF
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Q. In a circular loop of radius R carrying a current I, what is the magnetic field at the center of the loop?
A.
μ₀I/(2R)
B.
μ₀I/(4R)
C.
μ₀I/(2πR)
D.
μ₀I/(4πR)
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Solution
The magnetic field B at the center of a circular loop of radius R carrying current I is given by B = μ₀I/(2R).
Correct Answer: A — μ₀I/(2R)
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Q. In a circular loop of radius R carrying a current I, what is the magnetic field at the center of the loop according to the Biot-Savart Law?
A.
B = (μ₀I)/(2R)
B.
B = (μ₀I)/(4R)
C.
B = (μ₀I)/(R)
D.
B = (μ₀I)/(πR)
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Solution
The magnetic field at the center of a circular loop of radius R carrying current I is given by B = (μ₀I)/(2R).
Correct Answer: A — B = (μ₀I)/(2R)
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Q. In a circular path of radius r around a long straight wire carrying current I, what is the line integral of the magnetic field?
A.
0
B.
μ₀I
C.
μ₀I/2
D.
μ₀I/4
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Solution
The line integral of B around the path is equal to μ₀I by Ampere's Law.
Correct Answer: B — μ₀I
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