Physics Study Resources for Competitive Exams

Physics

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Q. What is the power consumed by a 6Ω resistor when a current of 2A flows through it? (2023)

A. 12W
B. 24W
C. 6W
D. 8W

Solution

Power (P) is given by P = I²R = (2A)² * 6Ω = 4 * 6 = 24W.

Correct Answer: A — 12W

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Q. What is the power consumed by a 6Ω resistor when a current of 3A flows through it? (2021)

A. 18W
B. 9W
C. 36W
D. 12W

Solution

Power (P) is given by P = I^2 * R = (3A)^2 * 6Ω = 9 * 6 = 54W.

Correct Answer: A — 18W

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Q. What is the power consumed in an AC circuit with a voltage of 230V and a current of 5A with a power factor of 0.8? (2023)

A. 920W
B. 1150W
C. 115W
D. 460W

Solution

Power = V × I × Power Factor = 230V × 5A × 0.8 = 920W.

Correct Answer: A — 920W

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Q. What is the power factor in a circuit with a resistance of 5 ohms and a reactance of 5 ohms? (2022)

A. 0
B. 0.5
C. 1
D. √2/2

Solution

Power factor = R/Z = 5/√(5² + 5²) = 5/√50 = √2/2.

Correct Answer: D — √2/2

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Q. What is the power factor in an AC circuit with a phase angle of 30 degrees? (2022)

A. 0.5
B. 0.866
C. 1
D. 0.707

Solution

The power factor is cos(30°) = √3/2 ≈ 0.866.

Correct Answer: B — 0.866

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Q. What is the power factor of a circuit with a resistance of 30Ω and a reactance of 40Ω? (2023)

A. 0.6
B. 0.75
C. 0.8
D. 1.0

Solution

Power factor = R/Z where Z = √(R² + X²). Calculate.

Correct Answer: A — 0.6

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Q. What is the power factor of a circuit with a resistance of 4Ω and a reactance of 3Ω? (2021)

A. 0.6
B. 0.8
C. 1.0
D. 0.75

Solution

Power factor = R/Z = R/√(R² + X²) = 4/√(4² + 3²) = 4/5 = 0.8.

Correct Answer: A — 0.6

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Q. What is the power factor of a circuit with a resistance of 5 ohms and a reactance of 5 ohms? (2022)

A. 0
B. 0.5
C. 1
D. √2/2

Solution

Power factor = R/Z = 5/√(5² + 5²) = 5/√50 = √2/2.

Correct Answer: D — √2/2

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Q. What is the power factor of a circuit with a resistance of 5Ω and an inductive reactance of 5Ω? (2022)

A. 0.5
B. 0.707
C. 1
D. 0

Solution

Power factor = R/Z = 5 / √(5² + 5²) = 5 / √50 = 0.707.

Correct Answer: B — 0.707

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Q. What is the power factor of a circuit with a resistance of 6Ω and a reactance of 8Ω? (2022)

A. 0.75
B. 0.8
C. 0.6
D. 1.0

Solution

Power factor = R/Z = R/√(R² + X²) = 6/√(6² + 8²) = 6/10 = 0.6.

Correct Answer: B — 0.8

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Q. What is the power factor of a circuit with a resistance of 8Ω and a reactance of 6Ω? (2023)

A. 0.5
B. 0.6
C. 0.8
D. 1.0

Solution

Power factor = R/Z, where Z = √(R² + X²) = √(8² + 6²) = 10. Thus, PF = 8/10 = 0.8.

Correct Answer: C — 0.8

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Q. What is the power factor of an AC circuit with a phase angle of 60°? (2022)

A. 0.5
B. 0.866
C. 1
D. 0.707

Solution

The power factor is cos(60°) = 0.5.

Correct Answer: B — 0.866

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Q. What is the power output of a motor that does 1200 J of work in 30 seconds?

A. 20 W
B. 40 W
C. 60 W
D. 80 W

Solution

Power = Work / Time = 1200 J / 30 s = 40 W.

Correct Answer: C — 60 W

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Q. What is the power output of a motor that does 3000 J of work in 15 seconds?

A. 200 W
B. 300 W
C. 400 W
D. 500 W

Solution

Power = Work / Time = 3000 J / 15 s = 200 W.

Correct Answer: B — 300 W

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Q. What is the pressure exerted by a force of 100 N over an area of 5 m²? (2023)

A. 20 Pa
B. 25 Pa
C. 15 Pa
D. 30 Pa

Solution

Pressure (P) = Force/Area = 100 N / 5 m² = 20 Pa.

Correct Answer: B — 25 Pa

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Q. What is the pressure exerted by a force of 200 N acting on an area of 4 m²? (2015)

A. 50 Pa
B. 100 Pa
C. 200 Pa
D. 400 Pa

Solution

Pressure = Force/Area = 200 N / 4 m² = 50 Pa.

Correct Answer: B — 100 Pa

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Q. What is the principal quantum number of an electron in the ground state of a hydrogen atom? (2022)

A. 0
B. 1
C. 2
D. 3

Solution

The ground state of hydrogen corresponds to n = 1.

Correct Answer: B — 1

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Q. What is the principal quantum number of an electron in the third energy level? (2023)

A. 1
B. 2
C. 3
D. 4

Solution

The principal quantum number (n) indicates the energy level. For the third energy level, n = 3.

Correct Answer: C — 3

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Q. What is the relationship between the frequency and the period of a wave? (2021)

A. Frequency is the square of the period
B. Period is the reciprocal of frequency
C. Frequency and period are unrelated
D. Period is the square root of frequency

Solution

The period T is the reciprocal of frequency f, given by T = 1/f.

Correct Answer: B — Period is the reciprocal of frequency

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Q. What is the relationship between the units of energy (Joule) and force (Newton)? (2021)

A. 1 J = 1 N·m
B. 1 J = 1 N/m
C. 1 J = 1 m/N
D. 1 J = 1 N^2

Solution

1 Joule is defined as the work done when a force of one Newton moves an object one meter, hence 1 J = 1 N·m.

Correct Answer: A — 1 J = 1 N·m

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Q. What is the relationship between the wavelength of light and the angle of diffraction in a grating? (2023)

A. Directly proportional
B. Inversely proportional
C. No relationship
D. Exponential relationship

Solution

The angle of diffraction is directly proportional to the wavelength of light used in a diffraction grating, as described by the grating equation.

Correct Answer: A — Directly proportional

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Q. What is the relationship between the wavelength of light and the angle of diffraction in a single-slit experiment? (2023)

A. Directly proportional
B. Inversely proportional
C. No relationship
D. Exponential relationship

Solution

The angle of diffraction is inversely proportional to the wavelength; as the wavelength increases, the angle of diffraction decreases.

Correct Answer: B — Inversely proportional

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Q. What is the resistance of a circuit if a current of 5A flows through it when a voltage of 25V is applied? (2022)

A. 5Ω
B. 10Ω
C. 15Ω
D. 20Ω

Solution

Using Ohm's law (R = V/I), R = 25V / 5A = 5Ω.

Correct Answer: B — 10Ω

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Q. What is the SI unit of electric charge? (2020)

A. Coulomb
B. Ampere
C. Volt
D. Ohm

Solution

The SI unit of electric charge is Coulomb (C).

Correct Answer: A — Coulomb

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Q. What is the significance of the Rydberg constant? (2022)

A. It determines the energy levels of an atom
B. It is used to calculate the wavelengths of spectral lines
C. It is a measure of atomic mass
D. It relates to the speed of light

Solution

The Rydberg constant is used to calculate the wavelengths of spectral lines in hydrogen and other hydrogen-like atoms.

Correct Answer: B — It is used to calculate the wavelengths of spectral lines

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Q. What is the significance of the wave function in quantum mechanics? (2023)

A. It describes the position of a particle
B. It gives the probability of finding a particle
C. It determines the mass of a particle
D. It is irrelevant

Solution

The wave function provides the probability distribution of a particle's position.

Correct Answer: B — It gives the probability of finding a particle

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Q. What is the specific heat capacity of a substance if it requires 500 J to raise the temperature of 2 kg of the substance by 10°C? (2021)

A. 25 J/kg°C
B. 50 J/kg°C
C. 100 J/kg°C
D. 200 J/kg°C

Solution

Specific heat capacity (c) = Q / (m * ΔT) = 500 J / (2 kg * 10°C) = 25 J/kg°C.

Correct Answer: B — 50 J/kg°C

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Q. What is the specific heat capacity of a substance if it requires 500 J to raise the temperature of 2 kg of the substance by 5°C? (2021)

A. 20 J/kg°C
B. 50 J/kg°C
C. 100 J/kg°C
D. 200 J/kg°C

Solution

Specific heat capacity (c) = Q / (m * ΔT) = 500 J / (2 kg * 5°C) = 50 J/kg°C.

Correct Answer: B — 50 J/kg°C

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Q. What is the specific heat capacity of a substance if it takes 500 J to raise the temperature of 2 kg of the substance by 5°C? (2021)

A. 20 J/kg°C
B. 50 J/kg°C
C. 100 J/kg°C
D. 200 J/kg°C

Solution

Specific heat capacity (c) = Q / (m * ΔT) = 500 J / (2 kg * 5°C) = 50 J/kg°C

Correct Answer: B — 50 J/kg°C

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Q. What is the specific heat capacity of water if it takes 4200 J to raise the temperature of 1 kg of water by 1°C? (2021)

A. 2100 J/kg°C
B. 4200 J/kg°C
C. 8400 J/kg°C
D. 1000 J/kg°C

Solution

The specific heat capacity of water is defined as the amount of heat required to raise the temperature of 1 kg of water by 1°C, which is given as 4200 J/kg°C.

Correct Answer: B — 4200 J/kg°C

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Physics

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