Physics II

Daffodil International University Faculty of Science & Information Technology Department of Computer Science & Engineering Midterm Examination, Fall 2026 Course Code: PHY102, Course Title: Physics II Level: 1 Term: 3 Batch: 71 Time: 01:30 Hrs Marks: 25 Answer ALL Questions [The figures in the right margin indicate the full marks and corresponding course outcomes. All portions of each question must be answered sequentially.] 1. a) Write Gauss's law for the electric flux through a closed surface. | 1 b) Recall the relationship between charge density and drift velocity. | 1 c) Define the magnetic moment of a current-carrying loop and state its SI unit. | 1 d) Explain the physical significance of μ. | 1 e) State Lenz's law and indicate the direction of induced current. | 1 2. a) In a molecular system, two equal and opposite charges, +q and -q, are separated by a small distance d. Point X is located at a distance from the charges. Obtain an expression for the electric potential at X. | 3 b) You find a capacitor in the physics laboratory shaped like a coaxial cable, consisting of two conducting cylindrical surfaces separated by an insulating medium. Establish the expression for its capacitance. | 4 c) A thin metallic strip carrying a current I is placed in a uniform magnetic field perpendicular to the direction of charge motion. A Hall voltage V_H develops across the strip. By balancing the electric and magnetic forces, derive an expression for the number of charge carriers per unit volume in terms of the measurable quantities. | 4 3. a) Two fixed point charges of +4 μC and +1 μC are placed 30 cm apart on a laboratory bench. A small test charge is placed on the line joining them. Determine the position where the test charge experiences zero net electrostatic force. | 2.5 b) The resistances of the four arms of a post office box are P = 10 Ω, Q = 10 Ω, R = 20 Ω and S = 25 Ω, respectively. What amount of resistance, when connected in parallel with S, will balance the post office box? | 2.5 c) A straight wire carrying a current of 4 A is placed near a point P. The point lies 5 cm perpendicular to the wire. The two lines joining P to the ends of a finite wire segment make angles of 30° and 60° with the wire. Draw the diagram and calculate the magnitude of the magnetic field at P due to the wire segment. | 2.5 d) A transformer converts an input voltage of 220 V to an output voltage of 2200V. If the primary coil has 500 turns and a resistance of 0.5 Ω, estimate the number of turns in the secondary coil and identify the type of transformer. | 2.5 Good Luck