Q1. A point charge +q is placed at a distance of 2R from the centre of an uncharged, conducting hollow sphere of radius R. The sphere is then earthed. What is the net electrostatic force on the charge +q?
Correct Answer: Option A (Zero)
Explanation: Detailed explanation will be updated shortly.
Q2. In a potentiometer experiment, the balancing length for a cell is L. If the length of the potentiometer wire is doubled and the current from the driver cell is halved, the new balancing length for the same cell will be:
Correct Answer: Option A (L)
Explanation: Detailed explanation will be updated shortly.
Q3. A proton, a deuteron (charge +e, mass 2m_p), and an alpha particle (charge +2e, mass 4m_p) are accelerated from rest through the same potential difference V. They then enter a uniform magnetic field B, perpendicular to their velocity. What is the ratio of the radii of their circular paths, r_p : r_d : r_α?
Correct Answer: Option A (1 : √2 : √2)
Explanation: Detailed explanation will be updated shortly.
Q4. A small bar magnet is dropped through a vertical copper tube. Its acceleration 'a' as it moves through the tube is best described by:
Correct Answer: Option A (a = g initially, and then a < g)
Explanation: Detailed explanation will be updated shortly.
Q5. An LCR series circuit is connected to an AC source with frequency ω. The circuit is operating at a frequency where the inductive reactance is twice the capacitive reactance (X_L = 2X_C). If the frequency of the source is now slightly decreased, the impedance of the circuit will:
Correct Answer: Option A (Increase)
Explanation: Detailed explanation will be updated shortly.
Q6. In a Young's Double Slit Experiment, the fringe width is β. The entire setup (slits, screen, and space in between) is submerged in a transparent liquid of refractive index 1.5. If the light source is monochromatic and remains in the air, what will be the new fringe width?
Correct Answer: Option A (β)
Explanation: Detailed explanation will be updated shortly.
Q7. The graph shows the variation of photoelectric current (i) with anode potential (V) for two different radiations. From the graph, we can conclude that:
(Graph shows two curves. Curve P has a higher saturation current but a less negative stopping potential than Curve Q.)
Correct Answer: Option A (Radiation P has higher intensity and higher frequency than Q.)
Explanation: Detailed explanation will be updated shortly.
Q8. For the given logic circuit, the output Y is equivalent to which single gate?
(A circuit diagram showing input A going into a NOT gate to produce A'. Then A' and B are inputs to a NAND gate, whose output is Y.)
Correct Answer: Option A (OR gate)
Explanation: Detailed explanation will be updated shortly.
Q9. In a plane electromagnetic wave propagating in a vacuum, the ratio of the average energy density of the magnetic field to the average energy density of the electric field is:
Correct Answer: Option A (1)
Explanation: Detailed explanation will be updated shortly.
Q10. A nucleus with mass number A=238 undergoes fission into two fragments with mass numbers approximately 119 each. According to the binding energy per nucleon curve, this process:
Correct Answer: Option A (Absorbs energy because breaking a nucleus requires energy.)
Explanation: Detailed explanation will be updated shortly.
Q11. An object is placed at a distance 'f' from a thin convex lens of focal length 'f'. A plane mirror is placed on the other side of the lens, perpendicular to the principal axis. For the final image to be formed at the position of the object itself, the distance of the plane mirror from the lens must be:
Correct Answer: Option A (f)
Explanation: Detailed explanation will be updated shortly.
Q12. The magnetic moment (μ) of an electron revolving in the n-th orbit of a hydrogen atom is related to its angular momentum (L) by the relation μ = (e/2m)L. If the electron makes a transition from the n=4 state to the n=2 state, the value of the ratio μ/L:
Correct Answer: Option A (Doubles)
Explanation: Detailed explanation will be updated shortly.
Q13. A wire is stretched such that its length is increased by 20%. Assuming the volume remains constant, the percentage change in its resistance is:
Correct Answer: Option A (20%)
Explanation: Detailed explanation will be updated shortly.
Q14. To design the core of an electromagnet, which is subjected to rapid cycles of magnetization and demagnetization, the material should have:
Correct Answer: Option A (High retentivity and high coercivity)
Explanation: Detailed explanation will be updated shortly.
Q15. Two concentric, thin metallic spheres of radii R1 and R2 (R2 > R1) are given charges Q1 and Q2 respectively. The potential at a point at a distance r from the centre, such that R1 < r < R2, is:
Correct Answer: Option A ((1/4πε₀) * (Q1/r + Q2/r))
Explanation: Detailed explanation will be updated shortly.
Q16. In a single-slit diffraction experiment, the width of the slit is halved. To keep the width of the central diffraction maximum unchanged, what modification is needed?
Correct Answer: Option A (The distance to the screen (D) should be doubled.)
Explanation: Detailed explanation will be updated shortly.
Q17. A Zener diode with a breakdown voltage of 5.6 V is used as a voltage regulator. The breakdown occurs primarily due to:
Correct Answer: Option A (The Avalanche effect, involving collision and ionization.)
Explanation: Detailed explanation will be updated shortly.
Q18. A step-down transformer operates on a 2.5 kV line and supplies a load with 20 A. The ratio of the primary winding to the secondary winding is 20:1. Assuming 100% efficiency, the current in the primary coil is:
Correct Answer: Option A (1 A)
Explanation: Detailed explanation will be updated shortly.
Q19. A parallel plate capacitor is charged by a battery. After charging, the battery is disconnected. Then, the plates are pulled apart to double the initial separation. The electrostatic energy stored in the capacitor:
Correct Answer: Option A (Becomes half)
Explanation: Detailed explanation will be updated shortly.
Q20. A charged particle enters a region of uniform magnetic field and electric field, where the fields are perpendicular to each other and also perpendicular to the velocity of the particle. The particle moves undeviated. The kinetic energy of the particle is K. If the electric field is switched off, the particle will move in a circular path. The kinetic energy of the particle will then be:
Correct Answer: Option A (K)
Explanation: Detailed explanation will be updated shortly.