Physics
Q. If the current in an AC circuit is I(t) = 5√2 sin(100t + π/4), what is the RMS current? (2021)
A.
5 A
B.
2.5 A
C.
7.07 A
D.
3.54 A
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Solution
The RMS current is I_rms = I_peak / √2 = 5√2 / √2 = 5 A.
Correct Answer: B — 2.5 A
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Q. If the current through a resistor is tripled, what happens to the power dissipated in the resistor? (2022)
A.
Increases by 3 times
B.
Increases by 9 times
C.
Remains the same
D.
Decreases by 3 times
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Solution
Power is proportional to the square of the current (P = I²R). If I is tripled, P increases by 3² = 9 times.
Correct Answer: B — Increases by 9 times
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Q. If the electric field at a point is 1000 N/C and the charge at that point is 5 µC, what is the force experienced by the charge?
A.
0.005 N
B.
0.05 N
C.
0.5 N
D.
5 N
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Solution
F = E * q = 1000 N/C * 5 × 10^-6 C = 0.005 N.
Correct Answer: B — 0.05 N
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Q. If the frequency of a vibrating tuning fork is 440 Hz, what is the time period of the vibration? (2023)
A.
0.00227 s
B.
0.005 s
C.
0.01 s
D.
0.0227 s
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Solution
The time period T is the reciprocal of frequency f, T = 1/f. Therefore, T = 1/440 ≈ 0.00227 s.
Correct Answer: A — 0.00227 s
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Q. If the frequency of a wave is halved, what happens to its wavelength? (2015)
A.
Halves
B.
Doubles
C.
Remains the same
D.
Increases by four times
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Solution
Wavelength is inversely proportional to frequency. If frequency is halved, wavelength doubles.
Correct Answer: B — Doubles
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Q. If the frequency of an AC source is doubled, how does the inductive reactance change? (2020)
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
Xl = 2πfL; if f is doubled, Xl also doubles.
Correct Answer: B — Halves
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Q. If the frequency of an AC source is doubled, what happens to the inductive reactance? (2014)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Inductive reactance XL = 2πfL, so if frequency f is doubled, XL halves.
Correct Answer: B — It halves
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Q. If the frequency of an AC source is doubled, what happens to the reactance of a capacitor? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The capacitive reactance Xc = 1/(2πfC) halves when the frequency f is doubled.
Correct Answer: B — It halves
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Q. If the inductance of a coil is 0.5H and the frequency is 60Hz, what is the inductive reactance? (2023)
A.
31.42 ohms
B.
18.85 ohms
C.
37.70 ohms
D.
25.13 ohms
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Solution
Xl = 2πfL = 2π × 60 × 0.5 = 31.42 ohms.
Correct Answer: A — 31.42 ohms
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Q. If the inductive reactance of a coil is 30Ω and the resistance is 10Ω, what is the total impedance? (2018)
A.
10Ω
B.
30Ω
C.
33.33Ω
D.
40Ω
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Solution
Total impedance Z = √(R² + (XL)²) = √(10² + 30²) = √(100 + 900) = √1000 = 31.62Ω.
Correct Answer: C — 33.33Ω
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Q. If the latent heat of fusion of ice is 334 J/g, how much heat is required to melt 50 g of ice? (2019)
A.
1670 J
B.
3340 J
C.
5000 J
D.
1000 J
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Solution
Heat required = mass × latent heat = 50 g × 334 J/g = 16700 J.
Correct Answer: A — 1670 J
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Q. If the magnetic field strength is doubled, what happens to the force experienced by a current-carrying conductor? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The force experienced by a current-carrying conductor in a magnetic field is directly proportional to the magnetic field strength. Therefore, if the magnetic field strength is doubled, the force also doubles.
Correct Answer: A — It doubles
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Q. If the magnetic field strength is doubled, what happens to the force on a current-carrying conductor in that field? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The force on a current-carrying conductor is directly proportional to the magnetic field strength, so if the field strength is doubled, the force also doubles.
Correct Answer: A — It doubles
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Q. If the magnetic field strength is doubled, what happens to the force on a current-carrying conductor? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The force on a current-carrying conductor is directly proportional to the magnetic field strength, so if the magnetic field strength is doubled, the force also doubles.
Correct Answer: A — It doubles
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Q. If the mass of the Earth were to double, what would happen to the gravitational force experienced by an object on its surface?
A.
It doubles
B.
It halves
C.
It quadruples
D.
It remains the same
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Solution
Gravitational force is directly proportional to mass. If mass doubles, force also doubles.
Correct Answer: A — It doubles
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Q. If the radius of the Earth were to increase by 50%, what would happen to the weight of an object on its surface?
A.
It increases by 50%
B.
It increases by 25%
C.
It decreases by 25%
D.
It remains the same
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Solution
Weight is inversely proportional to the square of the radius. If radius increases by 50%, weight decreases by 25%.
Correct Answer: C — It decreases by 25%
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Q. If the radius of the Earth were to increase while keeping its mass constant, what would happen to the gravitational acceleration at its surface?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
Gravitational acceleration g = GM/R². If R increases, g decreases.
Correct Answer: B — It decreases
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Q. If the radius of the Earth were to increase while keeping its mass constant, what would happen to the value of g? (2023)
A.
g increases
B.
g decreases
C.
g remains the same
D.
g becomes zero
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Solution
If the radius increases while mass remains constant, g decreases because g = G * M / r^2.
Correct Answer: B — g decreases
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Q. If the resistance of a conductor is doubled, what happens to the current flowing through it when the voltage remains constant? (2022)
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases by 1.5 times
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Solution
According to Ohm's law, I = V/R. If R is doubled, I will be halved.
Correct Answer: B — Halves
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Q. If the speed of light in a vacuum is 3 x 10^8 m/s, what is its speed in water (n = 1.33)?
A.
2.26 x 10^8 m/s
B.
2.25 x 10^8 m/s
C.
2.27 x 10^8 m/s
D.
2.28 x 10^8 m/s
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Solution
The speed of light in a medium is given by v = c/n. Thus, v = (3 x 10^8 m/s) / 1.33 ≈ 2.26 x 10^8 m/s.
Correct Answer: A — 2.26 x 10^8 m/s
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Q. If the speed of light in a vacuum is approximately 3 x 10^8 m/s, what is its value in km/s?
A.
300 km/s
B.
3000 km/s
C.
30000 km/s
D.
300000 km/s
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Solution
To convert m/s to km/s, divide by 1000. Therefore, 3 x 10^8 m/s = 300000 km/s.
Correct Answer: D — 300000 km/s
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Q. If the speed of light in vacuum is 3 x 10^8 m/s, what is its speed in glass (n = 1.5)?
A.
2 x 10^8 m/s
B.
2.5 x 10^8 m/s
C.
3 x 10^8 m/s
D.
1.5 x 10^8 m/s
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Solution
The speed of light in a medium is given by v = c/n. Therefore, v = (3 x 10^8 m/s) / 1.5 = 2 x 10^8 m/s.
Correct Answer: A — 2 x 10^8 m/s
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Q. If the speed of light is 3 x 10^8 m/s, what is its value in km/s? (2021)
A.
3 x 10^5 km/s
B.
3 x 10^6 km/s
C.
3 x 10^7 km/s
D.
3 x 10^8 km/s
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Solution
To convert m/s to km/s, divide by 1000. Therefore, 3 x 10^8 m/s = 3 x 10^5 km/s.
Correct Answer: A — 3 x 10^5 km/s
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Q. If the total current in an AC circuit is 5A and the voltage is 120V, what is the impedance? (2023)
A.
24Ω
B.
20Ω
C.
30Ω
D.
15Ω
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Solution
Impedance (Z) = Voltage (V) / Current (I) = 120V / 5A = 24Ω.
Correct Answer: B — 20Ω
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Q. If the voltage across a capacitor in an AC circuit is 100 V and the capacitive reactance is 50 ohms, what is the current? (2020)
A.
2 A
B.
0.5 A
C.
5 A
D.
10 A
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Solution
Using Ohm's law, I = V/Xc = 100 V / 50 ohms = 2 A.
Correct Answer: B — 0.5 A
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Q. If the voltage across a capacitor in an AC circuit is 100 V and the capacitive reactance is 50 Ω, what is the current through the capacitor? (2021)
A.
2 A
B.
0.5 A
C.
5 A
D.
10 A
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Solution
Using Ohm's law, I = V/Xc = 100 V / 50 Ω = 2 A.
Correct Answer: B — 0.5 A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50Ω, what is the current through the capacitor? (2023)
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Solution
Current (I) = Voltage (V) / Capacitive Reactance (XC) = 100V / 50Ω = 2A.
Correct Answer: B — 2A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50Ω, what is the current? (2021)
A.
2A
B.
0.5A
C.
5A
D.
100A
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Solution
Using Ohm's law, I = V/Xc = 100V/50Ω = 2A.
Correct Answer: B — 0.5A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50 ohms, what is the current? (2023)
A.
2A
B.
0.5A
C.
5A
D.
10A
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Solution
Using Ohm's law, I = V/Xc = 100V/50Ω = 2A.
Correct Answer: A — 2A
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Q. If the voltage across a capacitor is 100V and the capacitive reactance is 50 ohms, what is the current through the capacitor? (2022)
A.
2 A
B.
1 A
C.
0.5 A
D.
0.25 A
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Solution
I = V/Xc = 100/50 = 2 A.
Correct Answer: B — 1 A
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