FAD1022 UAS 2022-2023

Basic Physics II Final Examination (UAS) for Academic Session 2022/2023, Semester 2 at Universiti Malaya, PASUM programme.

Exam Information

Attribute Value
Course FAD1022 - Basic Physics II (Fizik Asas 2)
Academic Year 2022/2023
Semester 2
Date June 2023
Duration 3 hours
Format Section A (15 questions, compulsory) + Section B (5 questions, answer 3) + Section C (6 questions, answer 4)
Total Pages 19

Physical Constants Provided

  • Permittivity of free space: $\varepsilon_0 = 8.85 \times 10^{-12} \text{ F m}^{-1}$
  • Permeability of free space: $\mu_0 = 1.27 \times 10^{-6} \text{ H m}^{-1}$ or $4\pi \times 10^{-7} \text{ H m}^{-1}$
  • Mass of electron: $m_e = 9.11 \times 10^{-31} \text{ kg}$
  • Electron charge: $e = 1.6 \times 10^{-19} \text{ C}$
  • Planck's constant: $h = 6.63 \times 10^{-34} \text{ J s}$
  • Coulomb's constant: $k = 9 \times 10^{9} \text{ N m}^2 \text{ C}^{-2}$

Topic Distribution

Topic Section Marks Key Concepts
Electric Flux A 3 Electric Flux, Gauss's Law
Capacitors A, B 12+ Capacitors & Dielectrics, Energy stored
DC Circuits A, B 9+ EMF, Internal resistance, Kirchhoff's Laws
AC Circuits A, B 12+ AC Circuits, Reactance, Phasors, Impedance
Magnetism A, C 15+ Magnetism, Lorentz force, Ampere's Law
Electromagnetic Induction A, C 18+ Faraday's Law, Lenz's Law, Induced EMF
Transformers A, C 9+ Inductance & Transformers, Ideal transformer
Semiconductors A, C 9+ Semiconductors & Diodes, BJT circuits
Modern Physics A, C 12+ Photoelectric Effect, de-Broglie Wavelength
Nuclear Physics C 6 Radioactivity, Half-life

Question Breakdown

SECTION A (Compulsory - Answer ALL 15 Questions)

Question A1

  • Topic: Electric Flux
  • Concepts: Gauss's Law, Electric flux through tilted surface
  • Question: A uniform electric field $\mathbf{E}$ with magnitude $3.5 \times 10^{3} \text{ N C}^{-1}$ passes through a disk of radius $0.2 \text{ m}$. The area is tilted at angle $40°$ from perpendicular to $\mathbf{E}$. Calculate the electric flux through the disk.
  • Marks: 3
  • Formula: $\Phi_E = EA\cos\theta$

Question A2

  • Topic: Capacitors & Dielectrics
  • Concepts: Energy stored in capacitor
  • Question: Calculate the energy stored in a capacitor of $25 \mu\text{F}$ when it is charged to $3 \text{ mC}$.
  • Marks: 3
  • Formula: $U = \frac{Q^2}{2C}$

Question A3

  • Topic: DC Circuits
  • Concepts: EMF and Internal Resistance
  • Question: A battery has emf of $1.5 \text{ V}$. When connected to a circuit, the terminal voltage is $1.3 \text{ V}$ whilst current is $1.2 \text{ A}$. Compute the battery's internal resistance.
  • Marks: 3
  • Formula: $\varepsilon = V + Ir$

Question A4

  • Topic: AC Circuits
  • Concepts: Inductive reactance
  • Question: An inductor has reactance of $150 \Omega$ in a $60 \text{ Hz}$ a.c. circuit. Calculate the inductance of the inductor.
  • Marks: 3
  • Formula: $X_L = 2\pi fL$

Question A5

  • Topic: AC Circuits
  • Concepts: Capacitive and inductive reactance
  • Question: The reactance of an inductor and a capacitor are equal at $800 \text{ Hz}$. Calculate the ratio of the capacitive reactance to the inductive reactance at $80 \text{ Hz}$.
  • Marks: 3
  • Key relationship: $X_C \propto \frac{1}{f}$, $X_L \propto f$

Question A6

  • Topic: Magnetism
  • Concepts: Lorentz force, Magnetic torque
  • Parts:
    • (a) Two electrons are in a magnetic field-free region. Electron A is stationary, while electron B moves toward the +x-axis. A magnetic field is applied toward the +z-axis. Determine the direction of motion of each electron. [2 marks]
    • (b) A conductive loop with radius $r$ carries constant current $I$ in uniform magnetic field $\mathbf{B}$ perpendicular to the plane. Describe briefly the magnetic torque acting on the loop. [1 mark]
  • Marks: 3 total

Question A7

  • Topic: Magnetism
  • Concepts: Velocity selector, Crossed fields
  • Question: An electron moves across a velocity selector. Calculate the speed $v$ if the electron experiences no deflection due to electric field $5.2 \times 10^{5} \text{ V m}^{-1}$ and magnetic field $2.8 \times 10^{-3} \text{ T}$.
  • Marks: 3
  • Diagram: Parallel plates with E-field, B-field perpendicular
  • Formula: $v = \frac{E}{B}$

Question A8

  • Topic: Electromagnetic Induction
  • Concepts: Motional EMF
  • Question: An airplane with wingspan $40 \text{ m}$ flies horizontally north at $400 \text{ m s}^{-1}$ in a region where Earth's magnetic field is $60 \mu\text{T}$ directed $50°$ below horizontal. Calculate the magnitude of induced emf at the wingspan.
  • Marks: 3
  • Formula: $\varepsilon = B_{\perp}lv$

Question A9

  • Topic: Electromagnetic Induction
  • Concepts: Faraday's Law, Lenz's Law
  • Question: A bar magnet is held above the centre of a horizontal wire loop. The magnet is pulled away from the loop.
    • (a)(i) Redraw and label direction of induced magnetic field [1 mark]
    • (a)(ii) Label current through the resistor [1 mark]
    • (b) Determine positive polarity at A or B [1 mark]
  • Marks: 3
  • Diagram: Bar magnet with N pole above circular loop with resistor

Question A10

  • Topic: Inductance & Transformers
  • Concepts: Transformer operation
  • Question: Explain briefly why transformers must use AC instead of DC.
  • Marks: 3
  • Key concept: Changing flux required for induction

Question A11

  • Topic: Inductance & Transformers
  • Concepts: Ideal transformer equation
  • Question: An ideal transformer has 30 times number of turns on secondary that could produce $150 \text{ kV}$. If primary has 1000 turns, calculate the voltage across it.
  • Marks: 3
  • Formula: $\frac{V_s}{V_p} = \frac{N_s}{N_p}$

Question A12

  • Topic: Semiconductors & Diodes
  • Concepts: Diode operation, Forward/reverse bias
  • Question: A DC power supply is connected in series to a diode and resistor, but no current is detected. Determine TWO possible reasons and suggest ONE method to counter the issue.
  • Marks: 3

Question A13

  • Topic: Semiconductors & Diodes
  • Concepts: Diode circuit analysis
  • Question: A forward-biased germanium diode and $500 \Omega$ resistor are connected in series to a $10 \text{ V}$ DC power supply. Calculate current through the diode.
  • Marks: 3
  • Note: Germanium diode has forward voltage drop ~0.3V

Question A14

  • Topic: Photoelectric Effect
  • Concepts: Einstein's photoelectric equation
  • Parts:
    • (a) Indicate condition causing photoelectron ejection from metal surface [1 mark]
    • (b) Briefly explain why maximum kinetic energy $K_{max}$ does not depend on intensity of incident radiation [2 marks]
  • Marks: 3 total

Question A15

SECTION B (Answer THREE out of FIVE Questions)

Question B1

  • Topic: Electrostatics
  • Concepts: Electric field, Electric potential, Electric potential energy
  • Parts:
    • (a) Two negative charges arranged in right triangle: $q_1 = -6.0 \text{ nC}$, $q_2 = -5.0 \text{ nC}$. Distances: both 0.5 m from point A.
      • (i) Magnitude and direction of resultant electric field at point A [5 marks]
      • (ii) Magnitude of force if test charge $+4.0 \text{ nC}$ placed at A [1 mark]
    • (b) Two point charges $+15 \text{ nC}$ and $-15 \text{ nC}$ arranged in triangle with point X.
      • (i) Electric potential at X [4 marks]
      • (ii) Electric potential energy if charge $-8 \text{ nC}$ placed at X [2 marks]
  • Total Marks: 12

Question B2

  • Topic: Capacitors & Dielectrics
  • Concepts: Parallel plate capacitor, Capacitor combinations
  • Parts:
    • (a) Parallel-plate capacitor with dimensions $2.5 \text{ cm} \times 3.0 \text{ cm}$, separated by paper ($\varepsilon_r = 3.7$) with thickness $1.2 \text{ mm}$. Dielectric strength $16 \times 10^{6} \text{ V m}^{-1}$.
      • (i) Calculate capacitance [3 marks]
      • (ii) Calculate maximum potential difference $V_{max}$ [2 marks]
      • (iii) State what happens if $V > V_{max}$ [1 mark]
    • (b) Four capacitors ($5 \mu\text{F}$, $2 \mu\text{F}$, $4 \mu\text{F}$, $3 \mu\text{F}$) connected with $12 \text{ V}$ supply in circuit with switches.
      • (i) Equivalent capacitance [3 marks]
      • (ii) Charge stored in the $5 \mu\text{F}$ capacitor [3 marks]
  • Total Marks: 12

Question B3

  • Topic: DC Circuits
  • Concepts: Kirchhoff's Laws, Voltage divider
  • Parts:
    • (a) Using Kirchhoff's Voltage Law, determine $R_2$ in voltage divider circuit with $\varepsilon = 6.0 \text{ V}$, $R_1 = 2.0 \Omega$, $\Delta V_{out} = 2.0 \text{ V}$ [6 marks]
    • (b) Determine magnitude of current $I_3$ in circuit with multiple branches using Kirchhoff's Laws. Given: $12.0 \text{ V}$ and $10.0 \text{ V}$ sources, resistors $0.05 \Omega$, $1.5 \Omega$, $1.00 \Omega$ [6 marks]
  • Total Marks: 12

Question B4

  • Topic: AC Circuits
  • Concepts: RMS current, Reactance, Phasor diagrams
  • Parts:
    • (a) Determine RMS current when $240 \text{ V}$, $60 \text{ Hz}$ AC supply connected separately to:
      • (i) $23 \Omega$ resistor [2 marks]
      • (ii) $550 \mu\text{F}$ capacitor [2 marks]
      • (iii) $60 \text{ mH}$ inductor [2 marks]
    • (b) Two phasor diagrams shown at $t = 0$:
      • (i) First phasor: V at $\pi/2$, I at 0
      • (ii) Second phasor: I leads V by $\pi/4$
      • Sketch sinusoidal waves and state which signal leads for each [6 marks]
  • Total Marks: 12

Question B5

  • Topic: AC Circuits
  • Concepts: AC circuit analysis, Impedance, Power factor, Phasors
  • Question: AC circuit with resistor ($R_1$), two identical capacitors ($C_1$, $C_2$), and inductor ($L_1$), powered by $V_{rms} = 120 \text{ V}$ at $\omega = 60\pi \text{ rad s}^{-1}$.
    • (a) Switch at position A: Current across $R_1$ is $1.2 \text{ A}$. Calculate impedance given power factor is 47%. [3 marks]
    • (b) Switch at position B: Impedance is $24 \Omega$. Calculate inductive reactance of $L_1$ if voltage leads current by $76.11°$. [3 marks]
    • (c) Switches B and C closed: Current across inductor is $4.85 \text{ A}$ and total current is $3 \text{ A}$. Calculate current across $C_2$. Explain why current across $C_2$ could have two values. [6 marks]
  • Total Marks: 12
  • Diagram: Parallel AC circuit with switch positions A, B, C

SECTION C (Answer FOUR out of SIX Questions)

Question C1

  • Topic: Magnetism
  • Concepts: Magnetic force between conductors, Ampere's Law
  • Parts:
    • (a) Long straight wire with $I_1 = 3.0 \text{ A}$ placed $2.0 \text{ cm}$ from square loop ($I_2$, sides $4.0 \text{ cm}$). Resultant magnetic force on loop is $4.0 \times 10^{-6} \text{ N}$. Calculate $I_2$. [6 marks]
    • (b) Long wire with radius $R$ carries current $I$.
      • (i) Using Ampere's Law, prove $B = \frac{\mu_0 I r}{2\pi R^2}$ inside wire [2 marks]
      • (ii) Calculate magnetic field at $2.0 \text{ mm}$ from inside surface if $R = 10 \text{ mm}$, $I = 3.0 \text{ A}$ [2 marks]
      • (iii) If positive charge moves toward wire, determine direction of magnetic force [2 marks]
  • Total Marks: 12
  • Diagrams: Wire and square loop configuration; cylindrical wire with current

Question C2

  • Topic: Electromagnetic Induction
  • Concepts: Faraday's Law, Motional EMF
  • Parts:
    • (a) Coil with 12 turns, radius $2.50 \text{ cm}$, resistance $2.0 \Omega$. Magnetic field $B$ increases at $0.50 \text{ T s}^{-1}$.
      • (i) Calculate induced emf [3 marks]
      • (ii) Calculate induced current [3 marks]
    • (b) Two conducting rails distance $\ell = 1.20 \text{ m}$ apart in uniform $B = 2.50 \text{ T}$ perpendicular to rail plane, with resistor $R = 6 \Omega$.
      • (i) Calculate speed required to generate current $0.50 \text{ A}$ [4 marks]
      • (ii) Identify point with highest potential (C or D) [1 mark]
      • (iii) If velocity direction reversed, determine direction of induced current [1 mark]
  • Total Marks: 12

Question C3

  • Topic: Electromagnetic Induction, Inductance & Transformers
  • Concepts: Rotating coil EMF, Induced current, Transformer
  • Parts:
    • (a) Rectangular loop area $0.10 \text{ m}^2$ rotating at $60 \text{ rev/s}$ with axis perpendicular to $B = 0.20 \text{ T}$. 1000 turns. Calculate maximum induced voltage. [3 marks]
    • (b) Rectangular coil $5.0 \text{ cm} \times 8.0 \text{ cm}$, 75 turns, total resistance $8.0 \Omega$. Plane perpendicular to $B$. Calculate rate of change of $B$ to induce current $0.10 \text{ A}$. [3 marks]
    • (c) Ideal transformer with turns ratio (primary:secondary) = $3:25$. $600 \text{ V}$ connected to primary, $14.0 \Omega$ resistor on secondary.
      • (i) Voltage in secondary coil [3 marks]
      • (ii) Current in primary coil [3 marks]
  • Total Marks: 12

Question C4

  • Topic: Inductance & Transformers
  • Concepts: Self-inductance, Induced EMF, Energy stored
  • Parts:
    • (a) Inductor coil with 50 turns. $70 \text{ mWb}$ flux when $4.0 \text{ A}$ passes through.
      • (i) Calculate inductance [3 marks]
      • (ii) If current decreases to zero in $9.5 \text{ ms}$, calculate induced emf [3 marks]
    • (b) Calculate energy stored in solenoid self-inductance with 800 turns, radius $1.0 \text{ cm}$, length $4.5 \text{ cm}$, current $10.0 \text{ A}$. [6 marks]
  • Total Marks: 12

Question C5

  • Topic: Semiconductors & Diodes, Operational Amplifiers
  • Concepts: BJT transistor, Amplifier circuit analysis
  • Question: For BJT amplifier circuit with $\beta = 50$, $+10 \text{ V}$ supply, $240 \text{ k}\Omega$ base resistor, $1 \text{ k}\Omega$ collector resistor, $500 \Omega$ emitter resistor.
    • (a) Determine:
      • (i) $I_B$ [4 marks]
      • (ii) $I_C$ [3 marks]
    • (b) Determine:
      • (i) $V_{CE}$ [2 marks]
      • (ii) Effect to $V_{CE}$ if $\beta$ increases [3 marks]
  • Total Marks: 12
  • Diagram: Common-emitter BJT amplifier circuit

Question C6

  • Topic: Photoelectric Effect, Nuclear Physics
  • Concepts: Photoelectric equation, Radioactive decay
  • Parts:
    • (a) Photoelectric experiment with cathode exposed to frequencies $6.9 \times 10^{14} \text{ Hz}$ and $11.8 \times 10^{14} \text{ Hz}$. Maximum kinetic energies $0.49 \text{ eV}$ and $2.5 \text{ eV}$.
      • (i) Sketch graph of $K_{max}$ against frequency, label values [3 marks]
      • (ii) Determine Planck's constant from graph [3 marks]
    • (b) Geiger counter placed $30 \text{ cm}$ from radioactive source. Initial count rate $7.5 \times 10^{3}$ per minute. After $2.0$ hours, reading is $5.4 \times 10^{3}$ per minute.
      • (i) Calculate decay constant [3 marks]
      • (ii) Calculate half-life of source [3 marks]
  • Total Marks: 12

Key Topics Tested

[!important] Comprehensive Coverage This exam covers the full FAD1022 syllabus:

Electrostatics & DC Circuits (25%)

  • Electric flux calculations
  • Capacitor energy and combinations
  • DC circuit analysis with Kirchhoff's Laws

AC Circuits (25%)

  • Reactance calculations (capacitive and inductive)
  • Phasor diagrams and phase relationships
  • AC circuit impedance and power factor

Magnetism & Electromagnetism (30%)

  • Lorentz force and magnetic fields
  • Faraday's Law and induced EMF
  • Ampere's Law applications
  • Transformers and inductance

Modern & Semiconductor Physics (20%)

  • Photoelectric effect analysis
  • de Broglie wavelength
  • Diode and BJT circuits
  • Radioactive decay

Notable Question Patterns

  1. Heavy calculation emphasis — Most questions require numerical computation
  2. Diagram interpretation — Many questions require analyzing circuit diagrams and field configurations
  3. Multi-part questions — Section B and C questions have interconnected parts building on previous answers
  4. Conceptual explanations — Mixed with calculations (e.g., transformer AC requirement, photoelectric effect explanations)

Related

Concepts Referenced