Physics
Q. In an RLC circuit, if the resistance is 6Ω, inductive reactance is 8Ω, and capacitive reactance is 4Ω, what is the total impedance? (2021)
A.
10Ω
B.
12Ω
C.
14Ω
D.
16Ω
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Solution
Total impedance Z = √(R² + (XL - XC)²) = √(6² + (8 - 4)²) = √(36 + 16) = √52 ≈ 10Ω.
Correct Answer: B — 12Ω
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Q. In an RLC circuit, if the resistance is increased, what happens to the quality factor (Q)? (2021)
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The quality factor Q is inversely proportional to resistance. Increasing resistance decreases Q.
Correct Answer: B — Decreases
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Q. In an RLC series circuit, if the inductive reactance is greater than the capacitive reactance, the circuit is said to be: (2022)
A.
Resonant
B.
Inductive
C.
Capacitive
D.
Purely resistive
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Solution
If the inductive reactance (XL) is greater than the capacitive reactance (XC), the circuit is inductive.
Correct Answer: B — Inductive
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Q. In an RLC series circuit, if the resistance is 10 Ω, inductance is 0.1 H, and capacitance is 100 μF, what is the resonant frequency? (2023)
A.
50 Hz
B.
100 Hz
C.
159 Hz
D.
200 Hz
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Solution
The resonant frequency f0 = 1/(2π√(LC)) = 1/(2π√(0.1 * 100e-6)) = 159 Hz.
Correct Answer: C — 159 Hz
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Q. In an RLC series circuit, if the total impedance is 50 ohms and the resistance is 30 ohms, what is the reactance? (2020)
A.
40 ohms
B.
30 ohms
C.
20 ohms
D.
10 ohms
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Solution
Using Z = √(R² + X²), we find X = √(Z² - R²) = √(50² - 30²) = √(2500 - 900) = √1600 = 40 ohms.
Correct Answer: A — 40 ohms
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Q. In which direction does the magnetic field line emerge from a bar magnet? (2022)
A.
From North to South
B.
From South to North
C.
In a circular path
D.
Randomly
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Solution
Magnetic field lines emerge from the north pole and enter the south pole of a bar magnet.
Correct Answer: A — From North to South
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Q. The dimensional formula for frequency is: (2023)
A.
[T^-1]
B.
[M^0 L^0 T^-1]
C.
[M^1 L^1 T^-1]
D.
[M^0 L^1 T^0]
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Solution
Frequency is defined as the number of cycles per unit time, hence its dimensional formula is [T^-1].
Correct Answer: A — [T^-1]
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Q. The dimensional formula for velocity is: (2022)
A.
[M^0 L^1 T^-1]
B.
[M^1 L^1 T^0]
C.
[M^1 L^0 T^-1]
D.
[M^0 L^0 T^1]
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Solution
Velocity is defined as displacement per unit time, hence its dimensional formula is [M^0 L^1 T^-1].
Correct Answer: A — [M^0 L^1 T^-1]
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Q. The force on a charged particle moving in a magnetic field is maximum when the angle between the velocity and the magnetic field is: (2021)
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
45 degrees
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Solution
The force on a charged particle moving in a magnetic field is maximum when the angle between the velocity and the magnetic field is 90 degrees.
Correct Answer: B — 90 degrees
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Q. The force on a charged particle moving in a magnetic field is maximum when: (2021)
A.
The particle moves parallel to the field
B.
The particle moves perpendicular to the field
C.
The particle is at rest
D.
The particle moves in a circular path
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Solution
The force on a charged particle moving in a magnetic field is maximum when the particle moves perpendicular to the field.
Correct Answer: B — The particle moves perpendicular to the field
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Q. The frequency of a tuning fork is 440 Hz. What is the time period of the sound wave produced? (2022)
A.
0.00227 s
B.
0.0045 s
C.
0.01 s
D.
0.005 s
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Solution
Time period (T) = 1 / frequency (f) = 1 / 440 Hz ≈ 0.00227 s.
Correct Answer: A — 0.00227 s
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Q. The maximum displacement of a wave from its rest position is called what? (2022)
A.
Amplitude
B.
Wavelength
C.
Frequency
D.
Period
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Solution
The maximum displacement from the rest position is defined as the amplitude of the wave.
Correct Answer: A — Amplitude
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Q. The resonant frequency of an RLC circuit is given by which formula? (2022)
A.
f = 1/(2π√(LC))
B.
f = 2π√(LC)
C.
f = LC
D.
f = R/(2πL)
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Solution
The resonant frequency f of an RLC circuit is given by f = 1/(2π√(LC)).
Correct Answer: A — f = 1/(2π√(LC))
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Q. The unit of electric charge in the SI system is: (2022)
A.
Coulomb
B.
Ampere
C.
Volt
D.
Ohm
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Solution
Coulomb (C) is the SI unit of electric charge.
Correct Answer: A — Coulomb
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Q. What happens to the magnetic field lines when a magnet is cut into two pieces? (2021)
A.
They disappear
B.
They become weaker
C.
Each piece becomes a magnet with its own field
D.
They merge into one
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Solution
When a magnet is cut into two pieces, each piece becomes a magnet with its own north and south poles, thus maintaining the magnetic field lines.
Correct Answer: C — Each piece becomes a magnet with its own field
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Q. What happens to the magnetic field when the current in a solenoid is reversed? (2023)
A.
It remains the same
B.
It disappears
C.
It reverses direction
D.
It doubles
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Solution
When the current in a solenoid is reversed, the direction of the magnetic field also reverses.
Correct Answer: C — It reverses direction
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Q. What happens to the magnetic field when the distance from a long straight conductor is doubled? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The magnetic field around a long straight conductor decreases with distance. Specifically, it is inversely proportional to the distance from the conductor.
Correct Answer: B — It halves
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Q. What is the base unit of temperature in the SI system? (2020)
A.
Celsius
B.
Fahrenheit
C.
Kelvin
D.
Rankine
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Solution
The base unit of temperature in the SI system is Kelvin (K).
Correct Answer: C — Kelvin
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Q. What is the capacitance of a capacitor that stores 10 µC of charge at a potential difference of 5 V?
A.
2 µF
B.
5 µF
C.
10 µF
D.
20 µF
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Solution
C = Q/V = 10 × 10^-6 C / 5 V = 2 × 10^-6 F = 2 µF.
Correct Answer: A — 2 µF
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Q. What is the capacitive reactance of a capacitor of 10μF at a frequency of 60 Hz? (2016)
A.
265.26Ω
B.
159.15Ω
C.
100Ω
D.
50Ω
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Solution
Capacitive reactance Xc = 1 / (2πfC) = 1 / (2π * 60 * 10e-6) = 265.26Ω.
Correct Answer: A — 265.26Ω
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Q. What is the capacitive reactance of a capacitor with a capacitance of 10μF at a frequency of 50Hz? (2020)
A.
318.31 ohms
B.
159.15 ohms
C.
31.83 ohms
D.
15.92 ohms
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Solution
Xc = 1 / (2πfC) = 1 / (2π × 50 × 10 × 10^-6) = 318.31 ohms.
Correct Answer: A — 318.31 ohms
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Q. What is the change in internal energy of a gas that absorbs 300 J of heat and does 100 J of work on the surroundings? (2020)
A.
200 J
B.
300 J
C.
400 J
D.
500 J
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Solution
Change in internal energy (ΔU) = Q - W = 300 J - 100 J = 200 J.
Correct Answer: A — 200 J
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Q. What is the change in internal energy of a system if 200 J of heat is added and 50 J of work is done by the system?
A.
150 J
B.
250 J
C.
200 J
D.
100 J
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Solution
Using the first law of thermodynamics, ΔU = Q - W = 200 J - 50 J = 150 J.
Correct Answer: A — 150 J
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Q. What is the change in internal energy of a system if 300 J of heat is added and 100 J of work is done by the system? (2021)
A.
200 J
B.
300 J
C.
400 J
D.
500 J
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Solution
Using the first law of thermodynamics: ΔU = Q - W = 300 J - 100 J = 200 J.
Correct Answer: A — 200 J
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Q. What is the current through a 10Ω resistor connected to a 20V battery? (2020)
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Solution
Using Ohm's law, I = V/R = 20V / 10Ω = 2A.
Correct Answer: B — 2A
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Q. What is the current through a 12Ω resistor connected to a 24V battery? (2023)
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Solution
Using Ohm's law, I = V/R = 24V / 12Ω = 2A.
Correct Answer: B — 2A
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Q. What is the current through a 12Ω resistor when a voltage of 48V is applied? (2023)
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Solution
Using Ohm's law, I = V/R = 48V / 12Ω = 4A.
Correct Answer: B — 6A
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Q. What is the current through a 15Ω resistor connected to a 45V source? (2021)
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Solution
Using Ohm's law, I = V/R = 45V / 15Ω = 3A.
Correct Answer: A — 3A
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Q. What is the direction of the magnetic field around a straight conductor carrying current? (2023)
A.
From north to south
B.
Clockwise
C.
Counterclockwise
D.
Radially outward
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Solution
The direction of the magnetic field around a straight conductor carrying current is counterclockwise when viewed from the positive end of the conductor.
Correct Answer: C — Counterclockwise
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Q. What is the effect of a dielectric material on the capacitance of a capacitor? (2023)
A.
It decreases the capacitance
B.
It increases the capacitance
C.
It has no effect
D.
It makes the capacitor discharge
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Solution
Inserting a dielectric material increases the capacitance of a capacitor by reducing the electric field within it.
Correct Answer: B — It increases the capacitance
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