XII Physics

SECTION “A” – (MCQs – Multiple Choice Questions)

Q.1. Choose the correct answer.

i. During an Adiabatic change, the pressure and the volume formula of a gas given by

• PV = Const
• PV = Const
• (PV) = Const
• PV = Const

ii. The unit of specific heat is

• JkgC⁻¹
• JkgC
• Jkg⁻¹k⁻¹
• Jkg⁻¹C⁻¹

iii. The co-efficient of linear expansion is ________ times the coefficient of volume expansion.

• 1/2
• 1/3
• 1/4
• 1/5

iv. One joule per coulomb is called

• Farad
• Grass
• Ampere
• Volt

v. The dimension of resistance is

• ML²T³A²
• ML²T⁻³A²
• ML¹T²A³
• ML⁴T¹A⁵

vi. The ratio of the mass of proton to the mass of electron is

• 1832
• 1833
• 1836
• 1838

vii. The disintegration of a photon into electron and proton near a heavy nucleus is known as

• Annihilation
• β-decay
• α-decay
• Pair production

viii. RMS velocity of a gas molecule at absolute zero temperature is

• 9 x 10⁶ m/s
• 3 x 10³ m/s
• 27³ m/s
• Zero

ix. The value of Boltzman constant is

• 3.85 x 10⁻²³Jk⁻¹
• 2.185 x 10⁻¹² Jk⁻¹
• 1.62 x 10⁻²²Jk⁻¹
• 1.38 x 10⁻²³Jk⁻¹

x. The heat required to produce a unit change in the temperature of a unit mass of a substance is called

• Heat capacity
• Molar heat
• Specific heat
• Latent heat

xi. The semi conductor diode is used as

• Amplifier
• Rectifier
• Modulator
• Oscillator

xii. The path of a neutron moving normal to a magnetic field a lan.

• Straight line
• Circular
• Oval
• Sinusoidal

xiii. S.I. Unit of induction is

• Tesla
• Henry
• Watt
• Weber

xiv. The force per unit length of a current carrying conductor in a uniform magnetic field is given by

• IBL Cosθ
• IBL Sinθ
• IB Sinθ
• IB Cosθ

SECTION “B” – (Short Answer Question)

Q.2. (i) Derive the expression Cp-Cv = R1 the symbols have their usual meaning.

ii. Express a relation for Molar Specific Heat. Why are these two different Molar Specific Heat of a gas? Explain.

iii. How fast must a proton of mass 1.67 x 10⁻²⁷kg be moving if it is to follow a circular path of radius 2.0cm a magnetic field of 0.7 Tesla? (mp = 1.67 x 10⁻²⁷kg)

iv. An electron has a speed of 10⁶m/s. Find its energy in electron volts (me = 9.1 x 10⁻²¹kg)?

v. Compare the energy of a photon of wave length 2 x 10⁻⁶m with the energy of x-ray photon of wavelength 2 x 10⁻¹⁰m. (h = 6.63 x 10⁻³⁴J-s)?

vi. What minimum energy is required in an x-ray tube in order to produce x-rays with wave length of 0.1 x 10⁻¹⁰m (h = 6.63 x 10⁻³⁴J-s)

xii. A 250 volt voltmeter has a total resistance of 20,000Ω. What additional series resistance must be connected to it to increase it range to 400 volts?

viii. The law temperature reservoir of a car not engine is at -3°C and has an efficiency of 40%. It is desired to increase the efficiency to 50%. By how many degrees should the temperature of hot reservoir be increased?

ix. Derive the relation b = 3a, where

α= Coefficient of Linear Expansion
β= Coefficient of Volume Expansion

x. Derive the relation for force on a current casing conductors in a uniform magnetic field?

xi. State the first law of thermodynamics of apply this law to

• Isobaric process
• Isochoric process

xii. Define magnetic field. Derive the relation for the magnitude of magnetic field of induction B. Give its unit.

xiii. Explain Ohm’s law and give its limitations?

xiv. Define Radioactivity. Define a relation for law of radioactivity decay.

xv. The help period of ₁₀₄PO²¹⁰ is 140 days. By what percent does its activity decrease per week?

SECTION “C” – (Detailed Answer Questions)

Q.3. (a) What do you understand by capacitance of a capacitor. Derive an expression for the capacitance of a parallel plate capacitor with some dielectric between its place?
Q.3. (b) What is a transformer? On what principle does it work? What is the difference between a step-up and step-down transformer?

Q.4. (a) What do you understand by Photoelectric Effect.

OR

Write down the definition of work function, stopping potential and thresh old frequency. Establish the relation between work function and the threshold freqency?

Q.4. (b) What do you understand by the frame of reference and inertial frame of reference? Give one example of each from daily life?

Q.5. (a) Derive the equation for couple of torque acting on a current caring rectangular coil suspended in a uniform magnetic field?
Q.5. (b) With the help of diagram describe how a galvanometer is converted into an ammeter. Derive the equation for shunt resistance?