Physics Pre-Test Examination 2024 - Girdih
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Questions and Answers

When an electric dipole is placed in a uniform electric field, it experiences:

  • Both a net force and torque (correct)
  • A net force
  • Neither a net force nor a torque
  • A torque

    • Which of the following is the S.I unit of dipole moment?

  • Coulomb
  • Coulomb/sec
  • Ampere
  • Coulomb-meter (correct)

    • Three capacitors each of capacity C are connected in parallel. Their equivalent capacitance will be:

  • 1/3C
  • C/3
  • 3/C
  • 3C (correct)

    • The relation between the electric field 'E' and the electric potential 'V' is:

    <p>E=-dV/dx​ (C)</p> Signup and view all the answers

    How does the capacity of a parallel plate capacitor change when the separation between the plates is decreased?

    <p>Increases (D)</p> Signup and view all the answers

    The relation between drift velocity (V) and current density(J) is:

    <p>J = neV (A)</p> Signup and view all the answers

    Magnetic field due to a toroidal solenoid is independent of:

    <p>None of these (D)</p> Signup and view all the answers

    The magnetic lines of force inside a bar magnet:

    <p>Are from S-pole to N-pole of the magnet (B)</p> Signup and view all the answers

    Lenz's Law is based on the principle of:

    <p>Conservation of angular momentum (D)</p> Signup and view all the answers

    Two parallel conductors carrying current in the same direction will:

    <p>Attract each other (D)</p> Signup and view all the answers

    The role of self-inductance is equivalent to:

    <p>Inertia (B)</p> Signup and view all the answers

    A transformer can work:

    <p>Only for A.C (A)</p> Signup and view all the answers

    The phase difference between current and voltage in an A.C. circuit containing inductance only is:

    <p>90 (A)</p> Signup and view all the answers

    Which of the following electromagnetic waves is used in the treatment of cancer?

    <p>Gamma ray (B)</p> Signup and view all the answers

    Which of the following series of hydrogen spectrum lies in the visible region of the electromagnetic spectrum?

    <p>Balmer (B)</p> Signup and view all the answers

    When magnification of a mirror is found to be m=1.5, the type of mirror is:

    <p>Concave mirror (B)</p> Signup and view all the answers

    The refractive index of a medium is minimum for:

    <p>Red light (A)</p> Signup and view all the answers

    Which of the following phenomenon can not be explained through ray optics ?

    <p>Diffraction of light (C)</p> Signup and view all the answers

    The length of an astronomical telescope in normal adjustment is:

    <p>fo + fe (A)</p> Signup and view all the answers

    Huygen's wave theory of light cannot explain:

    <p>Photoelectric effect (D)</p> Signup and view all the answers

    According to de Broglie hypothesis, the wavelength of matter wave is given by:

    <p>λ = h/mv (D)</p> Signup and view all the answers

    If the ratio of 1st Bohr's orbit to the radius of the second Bohr's orbit is 1/4, the radius of the second Bohr's orbit is:

    <p>4r (D)</p> Signup and view all the answers

    If the forbidden energy gap in a substance is 1ev, the substance is a:

    <p>Semiconductor (A)</p> Signup and view all the answers

    When indium is doped to silicon as an impurity, the resulting material is:

    <p>N-type semiconductor (C)</p> Signup and view all the answers

    When a reverse bias is applied to a p-n junction, it:

    <p>Raises the potential barrier (B)</p> Signup and view all the answers

    Two equal charges, opposite in nature separated by a very small distance, are called what?

    <p>Electric dipole</p> Signup and view all the answers

    Write down the formula for electric flux according to Gauss's theorem.

    <p>Φ = E⋅A</p> Signup and view all the answers

    What is the S.I. unit for magnetic flux?

    <p>Weber</p> Signup and view all the answers

    What is the average value of A.C. for half cycle?

    <p>Zero</p> Signup and view all the answers

    What electromagnetic waves are used for the surgery of the human eye?

    <p>Infrared waves</p> Signup and view all the answers

    How will the width of fringes change if the distance of the screen is increased from the slits?

    <p>The width of fringes will increase</p> Signup and view all the answers

    Define threshold frequency.

    <p>Threshold frequency refers to the minimum frequency of light required to eject electrons from a metal surface.</p> Signup and view all the answers

    Write any two properties of nuclear force.

    <p>Nuclear forces are very strong but have a very short range, and they are independent of charge.</p> Signup and view all the answers

    What do you mean by depletion layer?

    <p>A depletion layer is a region within a semiconductor device where there is a lack of free charge carriers.</p> Signup and view all the answers

    State Kirchhoff's rules. Explain briefly how these rules are justified.

    <p>Kirchhoff's current law states that the algebraic sum of currents entering a junction is equal to the algebraic sum of currents leaving the junction, and Kirchhoff's voltage law states that the algebraic sum of potential differences around any closed loop in a circuit is zero.</p> Signup and view all the answers

    State Ampere's circuital law. Derive an expression for the induced magnetic field inside a solenoid.

    <p>Ampere's circuital law states that the line integral of the magnetic field B around a closed loop is proportional to the total current enclosed by the loop. The expression for the induced magnetic field B inside a solenoid is B = μ₀nI, where μ₀ is the permeability of free space, n is the number of turns per unit length of the solenoid, and I is the current flowing through the solenoid.</p> Signup and view all the answers

    Explain self-induction. Derive the expression for the coefficient of self-inductance and write down its unit.

    <p>Self-induction is the phenomenon where a changing current in a coil induces an electromotive force (EMF) in the same coil. The expression for the coefficient of self-inductance L is given by L = μ₀N²A/l, where μ₀ is the permeability of free space, N is the number of turns in the coil, A is the area of the coil, and l is the length of the coil. The unit of self-inductance is Henry (H).</p> Signup and view all the answers

    Derive an expression for average or mean value of alternating current for half cycle. The equation for an alternating current is I = 3√2 sin (100πt + π/4) A. Find the root mean square value of the current.

    <p>The average value of an alternating current over half a cycle is zero. The root mean square (RMS) value of the current is 3A.</p> Signup and view all the answers

    Explain Rutherford's alpha particle scattering experiment and conclude the Rutherford atomic model.

    <p>In Rutherford's alpha particle scattering experiment, alpha particles were fired at a thin gold foil. Most of the alpha particles passed through the foil undeflected, but some were deflected at large angles, and a few were even scattered back. This observation led to the Rutherford model, which proposed that an atom consists of a small, dense, positively charged nucleus surrounded by negatively charged electrons. The majority of alpha particles passed through the foil undeflected because most of the atom is empty space. The large-angle deflections were due to the interaction of alpha particles with the positive nucleus. The small number of alpha particles that were scattered back indicated that the nucleus is very small and dense.</p> Signup and view all the answers

    Explain forward and reverse biasing of a diode. Draw I-V graph for forward and reverse biasing.

    <p>In forward biasing, the p-type side of the diode is connected to the positive terminal of the battery and the n-type side to the negative terminal. This allows current to flow easily through the diode as the potential barrier is reduced. reverse biasing, the p-type side of the diode is connected to the negative terminal of the battery and the n-type side to the positive terminal. This increases the potential barrier and prevents current flow through the diode. The I-V graph for a forward-biased diode shows a steep increase in current as the voltage increases, while the I-V graph for a reverse-biased diode shows a very small current, close to zero, until a certain breakdown voltage is reached.</p> Signup and view all the answers

    Study Notes

    Physics Pre-Test Examination 2024 - Girdih (Jharkhand)

    • General Instructions:
      • The exam has two parts (Part A and Part B)
      • Part A is multiple choice (25 marks)
      • Part B is subjective (45 marks)
      • Answers must be written in the provided answer booklet
      • Part A questions are compulsory, with no negative marking
      • Part B includes various question types (short answer, long answer)
      • Neat diagrams are necessary where required

    Part A - Multiple Choice Questions

    • Electric Dipole in Uniform Electric Field:

      • Experiences a torque

    • SI Unit of Dipole Moment:

      • Coulomb-meter

    • Three Capacitors in Parallel:

      • Equivalent capacitance is 3C

    • Relation Between Electric Field and Potential:

      • E = -dV/dx

    • Change in Parallel Plate Capacitor Separation:

      • Decreasing separation increases capacitance

    • Drift Velocity and Current Density:

      • J = nev

    • Magnetic Field Due to Toroidal Solenoid:

      • Independent of current

    • Magnetic Field Lines Inside a Bar Magnet:

      • From South pole to North pole

    • Lenz's Law Principle:

      • Conservation of Energy

    • Two Parallel Conductors with Same Direction Current:

      • Attract each other

    • Self Inductance Role:

      • Equivalent to inertia

    • Transformer Operation:

      • Works with AC Current

    • AC Circuit with Inductance:

      • Phase difference between current and voltage is 90°

    • Electromagnetic Wave used in Cancer Treatment:

      • X-ray

    • Hydrogen Spectrum Visible Region Series:

      • Balmer series

    • Mirror Magnification:

      • m = 1.5 indicates a convex mirror

    • Refractive Index Minimum:

      • For red light

    • Phenomenon Not Explained by Ray Optics:

      • Diffraction of light

    Part B - Subjective Questions

    • Electric Flux (Gauss's Theorem):

      • Formula for electric flux is needed

    • SI Unit for Magnetic Flux:

      • Weber

    • Average AC Value for Half Cycle:

      • Formula or value is needed for this calculation

    • Electromagnetic Waves in Human Eye Surgery: Information needed on the specific type of electromagnetic wave

    • Width of Screen and Slits: Information on how width increase impacts fringe widths

    • Threshold Frequency Definition:

      • Definition of threshold frequency is needed

    • Two Properties of Nuclear Force: Information on the required properties of nuclear force

    • Depletion Layer Definition:

      • Definition of depletion layer is needed

    • Dipole Moment Definition and Unit:

      • Definition and cgs unit for a dipole moment

    • Torque Calculation of Electric Dipole:

      • Calculation using dipole moment and electric field

    • Parallel Combination of Identical Cells:

      • Circuit diagram and condition for maximum current

    • Magnetic Field of Circular Current-Carrying Coil:

      • Expression for magnetic field at the axis and center

    • Thin Lens Maker's Formula:

      • Formula to calculate focal length of the thin lens = (μ - 1) (1/R₁ - 1/R₂)

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    JAC Board 12th Physics Preboard Solution 2024 PDF

    Description

    Prepare for your Physics examination with this comprehensive pre-test that covers key concepts such as electric dipoles, capacitors, and magnetic fields. The quiz consists of multiple-choice questions and subjective questions, providing a thorough assessment of your understanding of the subject. Make sure to review your concepts thoroughly and practice neat diagrams where required.

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