1. The drift velocity is of the order of a few cm/s. But when we switch on a bulb, it glows instantly. How is this possible?
2. Define internal resistance.
3. If n identical resistors are connected in series first and then in parallel, Calculate the ratio of effective resistance in series to the effective resistance in parallel.
4. Define mobility.
5. State Ohm’s law.
6. State the principle of a potentiometer.
7. Write the colour coding of a carbon resistor of resistance 18000 Ω and a tolerance 10%
8. What is a thermistor?

   2 Marks Questions

9. Deduce Ohm’s law using the concept of drift velocity.
10. State Kirchhoff’s laws for electric networks.
11. Distinguish emf and terminal voltage.
12. Derive an expression for drift velocity.

    3 marks questions

13. A battery om emf E and internal resistance r gives a current 0.5 A with an external resistance of 12 Ω and a current 0.25 A with an external resistance of 25Ω. Calculate the internal resistance and emf of the cell.
14. An electric motor operating on a 50 V dc supply draws a current of 12A. If the efficiency of the motor is 30%, estimate the resistance of the windings of the motor.
15. Draw the diagram showing the experimental arrangement for determining the resistance of a given wire of unknown resistance.

    5 Marks Questions

16. (a)Explain how a potentiometer is used to determine the internal resistance of a primary cell.

    (b)State the factors affecting the internal resistance of a cell

ELECTRIC CHARGES AND FIELD

Max. Marks: 30                 Time: 75 minutes

(Please take care to complete the test in the prescribed time limit)

One mark Questions

1. Define electric flux.
2. How is the force between two charges affected when dielectric constant of the medium in which they are placed increases?
3. Name the physical quantity whose SI unit is NC^-1
4. Why two electric lines of force never intersect each other?
5. Define dielectric constant of a medium.
6. What is an ideal dipole?
7. Write the SI unit of electric dipole moment.
8. Calculate the number of electrons making a charge of -0.1 mC.
   2 Marks questions
9. Vehicles carrying inflammable materials have metallic ropes (or chains)touching the ground while in motion. Explain why is it necessary?
10. Derive an expression for the electric field intensity at a distance ‘r’ from a point charge ‘q’
11. Two point charges 4 μC and 2 μC are separated by a distance 1 m in air. At what point on the line joining the two charges is the electric field intensity zero?
12. Derive an expression for the work done in rotating a dipole through an angle θ in a uniform electric field.
    3 Marks Questions
13. Show that, in a uniform electric field, a dipole experiences only a torque, but no net force. Derive an expression for the torque experienced by a dipole in a uniform electric field.
14. Write three points of difference between mass and charge.
15. An electric dipole of length 2 cm is placed with its axis making an angle 60 degrees with respect to a uniform electric field of 10⁵ N/C. If it experiences a torque of 8 √3 Nm, calculate the
    (i) magnitude of charge on the dipole, and
    (ii) potential energy of the dipole.
    5 marks Questions
16. Using Gauss’ theorem, derive an expression for the electric field intensity at a point due to a uniformly charged spherical conducting shell when the point is
    (a) outside the sphere
    (b) on the sphere
    (c) inside the sphere

AISSCE 2006 PHYSICS QUESTION PAPER

Outside Delhi

1. Define the term electric dipole moment. Is it a scalar or a vector quantity.
2. The variation of potential difference V with length l in case of two potentiometers P and Q ia as shown. Which one of these two will you prefer for comparing the e.m.f.s of two primary cells?
   
3. de Broglie wavelength associated with an electron accelerated through a potential difference V is λ. What will be its wavelength when the accelerating potential is increased to 4 V?
4. Give any one difference between FAX and e-mail systems of communication.
5. Steel is preferred for making permanent magnets whereas soft iron is preferred for making electromagnets. Give one reason.
6. You are given ‘n’ resisitors, each of resistance ‘r’. These are first connected to get minimum possible resistance. In the second case, these are again connected differently to get maximum possible resistance. Compute the ratio of the minimum to the maximum values of resistance obtained.
7. Two capacitors of capacitance 6μF and 12μF are connected in series with a battery. The voltage across the 6 μF capacitor is 2 V. Compute the total battery voltage.
   OR
   A parallel plate capacitor with air between the plates has a capacitance of 8 pF. The separation between the plates is now reduced by half and the space between them is filled with a medium of dielectric constant 5. Calculate the value of the capacitance of the capacitor in the second case.
8. Draw a labelled ray diagram to show the image formation in a refracting type astronomcal telescope. Why should the diameter of theobjective of a telescope be large?
9. Draw a circuit diagram of a metre bridge and write the necessary mathematical relation used to determine the value of an unknownresistance. Why cannot such an arrangement be used for measuring very low resistances?
10. Which one of the two, an ammeter or a milliammeter, has a higher resistance and Why?
11. An alternating voltage of frequency f is applied across a series LCR circuit. Let f_r be the resonance frequency for the
    circuit. Will the current in the circuit lag, lead or remain in phase with the appiled voltage when (i)f>f_r (ii) f<f_r?Explain your answer in each case.
12. A point charge ‘q’ is placed at O as shown in the figure. Is V_P – V_Q positive or negative when (i) q>0 (ii) qJustify your answer.
    
13. Using Gauss’ theorem, show mathematically that for any point outside the shell, the field due to a uniformly charged thin sphericalshell is the same as if the entire charge of the shell is concentrated at the centre. Why do you expect the electric field inside the shellto be zero according to this theorem?
14. Distinguish between frequency modulation and amplitude modulation. Why is an FM signal less susceptible to noise than an AMsignal?
15. Write the order of frequency range and one use each of the following electromagnetic radiations:
    (i) Microwaves.
    (ii) Ultra – violet rays.
    (iii) Gamma rays.
16. Sketch a graph between frequency of incident radiations and stopping potential for a given photosensitive material. Whatinformation can be obtained from the value of the intercept on the potential axis?
    A source of light of frequency greater than the threshold frequency is placed at a distance of 1 m from the cathode of a photo cell. Thestopping potential is found to be V. If the distance of the light source from the cathode is reduced, explain giving reasons, what changewill you observe in the
    (i) photo electric current
    (ii) stopping potential
17. Define the term half – life period and and decay constant of a radio active substance. Write the SI units. Establish the relationship between the two.
18. A neutron is absorbed by a ⁶₃Li nucleus with the emission of an alpha particle.
    (i)Write the corresponding nuclear reaction.
    (ii) Calculate the energy released, in MeV, in this reaction.
    Given: mass of ⁶₃Li = 6.015126 u ; mass of neutron = 1.0086654 u ; mass of alpha particle = 4.0026044 u ; mass of triton = 3.0100000 u ; Take 1 u = 931 MeV /c²
19. When an inductor L and a resistor R in series are conected across a 12 V, 50 Hz supply, a current differs in phase from the applied voltage by π/3 radian. Calculate the value of R.
    OR
    A 0.5 m long metal rod PQ completes the circuit as shown in figure. The area of the circuit is perpendicular to the magnetic field of flux density 0.15 T. If the resistance of the total circuit is 3Ω , calculate the force needed to move the rod in the direction as indicated with a constant speed of 2 m/s.
    
20. State Faraday’s laws of electrolysis. Express these in mathematical notation. Name any two applications of electrolysis. NOT IN PRESENT SYLLABUS
21. What are eddy currents? How are these produced? In what sense are eddy currents considered undesirable in a transformer and how are these reduced in such a device?
22. A beam of light converges to a point P. A lens is placed in the path of the convergent beam 12 cm from P. At what point does the beam converge if the lens is
    

    1. a convex lens on focal length 20 cm
    2. a concave lens of focal length 6 cm?

    Do the required calculations.

23. Consider an optical communication system operating at λ ~ 800 nm. Suppose, only 1% of the optical source frequency is the available channel band – width for optical communication. How many channels can be accomodated for transmitting
    

    1. audio signals requiring a bandwidth of 8 kHz?
    2. Video TV signals requiring an approximate band width of 4.5 MHz?

    Support your answer with suitable calculations

24. Explain (i) forward biasing, (ii) Reverse Biasing of a P-N junction diode. With the help of a circuit diagram, explain the use of this device as a half wave rectifier.
25. Draw a neat and labelled diagram of a cyclotron. State the underlying principle and explain how a positively charged particle gets accelerated in this machine. Show mathematically that the cyclotron frequency does not depend upon the speed of the particle.OR
    State Biot – Savart law for the magnetic field due to a current carrying element. Use this law to obtain a formula for magnetic field at the centre of a circular loop of radius R carrying a steady current I. Sketch the magnetic field lines for a current loop clearly indicating the direction of the field.

SET -1

1. In a series LCR circuit, the voltages across an inductor, a capacitor and a resisitor are 30 V, 30V and 60 V respectively. What is the phase difference between the applied voltage and the current in the circuit?
2. Ultraviolet radiations of different frequencies f₁ and f₂ are incident on two photosensitive materials having work functions W₁ and W₂ (W₁ > W₂ respectively. The kinetic energy of the emitted electrons is same in both cases. Which one of the two radiations will be of higher frequency?
3. Define the term “activity” of a radio active nuclide. Write its S.I. unit.
4. An electron is moving along the +ve X axis in the presence of uniform magnetic field along +ve Y axis. What is the direction of force acting on it?
5. What should be the length of dipole antenna for a carrier wave of frequency 6 x 10⁸Hz?
6. Two point charges 4µC and -2µC are separated by a distance of 1 m in air. Calculate at what point on the line joining the two charges is the electric potential zero.
7. A voltage of 30 V is applied across a carbon resistor with first, second and third rings of blue, black and yellow colours respectively. Calculate the value of current, in mA, through the resisitor.
8. A galvanometer has a resistance of 30 Ω. It gives full scale deflection with a current of 2 mA. Calculate the value of the resistance needed to convert it into an ammeter of range 0 – 0.3 A.
9. Calculate the current drawn by the primary of a transformer which steps down 200 V to 20 V to operate a device of resistance 20 Ω. Assume the efficiency of the transformer to be 80%.
   OR
   An a.c. voltage of 100 V, 50 Hz is connected across a 20 Ω resistor and 2 mH inductor in series. Calculate (i) impedence of the circuit. (ii) rms current in the circuit.
10. Define resolving power of a compound microscope. How does the resolving power of a compound microscope change when
    (i) refractive index of the medium between the object and objective lens increases.
    (ii) wavelength of the radiation used is increased.
11. Draw a graph showing the variation of potential energy between a pair of nucleons as a function of their separation. Indicate the regions in which the nuclear force is (i) attractive (ii) repulsive
12. Two semiconducting materials X and Y as shown in in figure are made by doping germanium crystal with indium and arsenic respectively. The two are joined end to end and connected to a battery as shown.
    
    (i)Will the junction be forward biased or reverse biased?
    (ii) Sketch a V-I graph for this arrangement.
13. State Gauss Theorem in electrostatics. Apply this theorem to derive an expression for electric field intensity at a point near an infinitely long straight charged wire.
14. Explain the underlying principle of working of a parallel plate capacitor. If two similar plates, each of area A having surface charge densities +σ and -σ are separated by a distance d in air, write expressions for
    (i) the electric field at points between the two plates.
    (ii) the potential difference between the two plates.
    (iii) the capacitance of the capacitor so formed.
15. For the potentiometer circuit shown in the figure, points X and Y represent the two terminals of an unknown e.m.f. E’. A student observed that when the jockey is moved from the end A to the end B of the potentiometer wire, the deflection in the galvanometer remains in the same direction.
    What may be the two possible faults that could result in this observation?
    If the Galvanometer deflection at the end B is (i) more, (ii) less, than at the end A, which of the two faults listed above, would be there in the circuit?
    Give reasons in support of your answer.
    
    OR
    The given figure below shows a network of resistances R₁, R₂, R₃ and R₄. Usinf Kirchhoff’s laws, establish the balance condition for the network.
    
16. out of syllabus
17. Name the following constituent radiations of the electromagnetic spectrum which
    (i) produces intense heating effect.
    (ii) is absorbed by the ozone layer in the atmosphere.
    (iii) is used for studying crystal structure.
    Write one moreapplication for each of these radiations
18. A double convex lens of glass of refractive index 1.6 has its both surfaces of equal radii of curvature of 30 cm each. An object of height 5 cm is placed at a distance of 12.5 cm from the lens. Calculate the size of the image formed.
19. Draw a schematic diagram of the experimental arrangement used by Davisson and Germer to establish the wave nature of electrons. Explain briefly how the de-Broglie relation was experimentally verified in case of electrons.
20. Draw the graph to show the vaiation of binding energy per nucleon with mass number of different atomic nuclei. Calculate the binding energy per nucleon of ⁴⁰Ca₂₀ nucleus. Given mass of ⁴⁰Ca₂₀ nucleus = 39.962589 u ; mass of proton = 1.007825 u; mass of neutron = 1.008665 u and 1 u = 931 MeV/c²
21. Draw the circuit diagram of a common emitter amplifier using n-p-n transisitor. What is the phase difference between the input signaland output voltage? State two reasons why a common emitter amplifier is preferred to a common base amplifier.
22. Explain the formation of energy bands in solids. Draw energy band diagrams for (i) a conductor, and (ii) an intrinsic semiconductor
23. What is modulation? Explain the need of modulating a low frequency information signal. With the help of diagrams, differentiate between PAM and PDM
24. Write the acronym LASER in expanded form. State four reasons for preferring diode LASERS as light sources for optical communiation links.
25. Explain with the help of a diagram, the principle and construction of a cyclotron. Deduce an expression for the cyclotron frrequency and show that it does not depend on the speed of the charged particle.
    OR
    Distinguish the magnetic properties of dia-, para-, and ferro- magnetic substances in terms of (i) susceptibility (ii) magnetic permeability and (iii) coercivity. Give one example of each of these materials.
    Draw the field lines due to an external magnetic field near a (i) diamagnetic (ii) paramagnetic substance
26. Explain the term ‘inductive reactance’. Show graphically the variation of inductive reactance with frequency of the applied alternating voltage.
    An a.c. voltage E = E₀sin ωt is applied across a pure inductor of inductance L. Show mathematically that the current flowing through it lags the applied voltage by a phase angle of π/2
    OR
    Explain the term ‘capacitive reactance’. Show graphically the variation of capacitive reactance with frequency of the applied alternating voltage.
    An a.c. voltage E = E₀sin ωt is applied across a pure capacitor of capacitance C. Show mathematically that the current flowing through it leads the applied voltage by a phase angle of π/2
27. State the essential condition for diffraction of light to take place.
    Use Huygens’ Principle to explain diffraction of light due to a narrow sngle slit and the formation of a pattern of fringes obtained on the screen. Sketch the pattern of fringes formed due to diffraction at a single slit showing variation of itensity with angle θ
    OR
    What are coherent sources of light? Why are coherent sources required to obtain sustained interference pattern?
    State three characteristic features which distinguish the interfernce pattern due to two coeherently illuminated sources as compared to that observed in a diffraction pattern due to a single slit.