Physics-Practice-4

Practice questions

1. The torque produced by a force about a fixed axis is maximum when the angle between the position vector and the force is:
   • 0°
   • 30°
   • 60°
   • 90°
2. The angular momentum of a particle moving in a circle of radius r with momentum p is:
   • pr
   • p/r
   • p²r
   • r/p
3. The escape speed from the surface of a planet depends primarily on:
   • The mass of the escaping object only
   • The planet's mass and radius
   • The colour of the planet
   • The direction of the planet's rotation only
4. A metal rod has an original length of 2 m. Its coefficient of linear expansion is 1.2 × 10⁻⁵ K⁻¹. If its temperature rises by 50 K, what is the increase in length?
   • 0.12 mm
   • 0.60 mm
   • 1.20 mm
   • 12.0 mm
5. How much heat is required to raise the temperature of 0.5 kg of water by 10°C? Take the specific heat capacity of water as 4,200 J kg⁻¹ K⁻¹.
   • 2,100 J
   • 4,200 J
   • 21,000 J
   • 42,000 J
6. The apparent change in frequency heard when a sound source moves relative to an observer is called:
   • Diffraction
   • Doppler effect
   • Polarization
   • Resonance
7. Two sound waves of frequencies 256 Hz and 260 Hz are played together. What beat frequency is produced?
   • 2 Hz
   • 4 Hz
   • 258 Hz
   • 516 Hz
8. Which phenomenon demonstrates that light is a transverse wave?
   • Polarization
   • Reflection only
   • Refraction only
   • Dispersion only
9. Two capacitors of 6 μF and 3 μF are connected in parallel. What is their equivalent capacitance?
   • 2 μF
   • 3 μF
   • 9 μF
   • 18 μF
10. A cell has an emf of 12 V and an internal resistance of 1 Ω. If it supplies a current of 2 A, what is its terminal voltage while discharging?
    • 8 V
    • 10 V
    • 12 V
    • 14 V
11. In an ideal alternating-current generator, the induced emf is produced primarily by:
    • Chemical reaction
    • Change in magnetic flux through a coil
    • Constant electric charge at rest
    • Heating of the coil alone
12. What is the root-mean-square (RMS) value of a sinusoidal alternating current with a peak value of 10 A?
    • 5.00 A
    • 7.07 A
    • 10.00 A
    • 14.14 A
13. In a series AC circuit, the power factor is defined as:
    • The ratio of resistance to capacitance
    • The cosine of the phase angle between voltage and current
    • The ratio of voltage to frequency
    • The product of inductance and current
14. Which phenomenon causes unwanted circulating currents in the core of a transformer when magnetic flux changes?
    • Eddy currents
    • Photoelectric emission
    • Nuclear fission
    • Total internal reflection
15. What is the main function of a moderator in a typical nuclear fission reactor?
    • To slow down fast neutrons
    • To increase the speed of all neutrons
    • To remove all radioactive material
    • To convert neutrons into protons
16. The half-life of a radioactive isotope is 8 days. What fraction of the original radioactive nuclei remains after 24 days?
    • 1/2
    • 1/4
    • 1/8
    • 1/16
17. The image formed by a convex mirror for a real object placed in front of it is always:
    • Real and inverted
    • Virtual and erect
    • Real and enlarged
    • Inverted and enlarged
18. What is the work done by a conservative force when an object moves around a complete closed path and returns to its starting point?
    • Always positive
    • Always negative
    • Zero
    • Equal to the object's mass
19. At a standing-wave node, the displacement amplitude of the medium is:
    • Maximum
    • Half the maximum amplitude
    • Zero
    • Equal to the wavelength
20. What is the energy stored in an ideal inductor carrying a current I, if its inductance is L?
    • LI²
    • ½LI²
    • ½CV²
    • VI