Physics as a subject is always considered a difficult subject that requires special skills for excelling. There is an organised way to study Physics for scoring well. Student should have firstly the concept understanding then the application of the concepts in Numerical and other questions.
Guiding students on how they can score well with an organised approach, Physics teacher Saroj Mishra gives important topics and essential questions to revise for board exams.
Physics New Exam Pattern
This exam pattern is changed. In the question Paper there are four sections. Section A contains objective type questions. It has 20 questions each of 1 marks. Under this category multiple choice questions and fill in the blanks are introduced for the first time, these will play vital role in the scoring of the students in the subject.
Section B and Section C contains 7 questions of 2 marks and 3 marks respectively. Section D contains 3 questions of 5 marks. There is no overall choice, however internal choice is provided in 2 questions of 1 mark, 2 questions of 2 marks, 1 question of 3 marks and all 3 questions of 5 marks.
Topic weightage
1. Electrostatics and current electricity: 16 marks.
2. Magnetic effects of current, magnetism, electromagnetic induction and alternating: 17 marks.
3. EM waves and Optics: 18marks.
4. Dual nature of matter and radiation, atoms and nuclei:12 marks
5. Electronic devices: 7 marks
How to prepare for Physics exam?
• Best way of preparing is practice the derivations, diagrams associated and the related numerical.
• Study thoroughly from NCERT book. You must study examples and the exercise given at the end.
• Solve 3 to 5 practice papers after completing the revision will give the confidence to the students as well the specific points which they need to remember.
• Do not bother yourself much if any particular question is not striking at that moment, proceed further later on you can get back to that question.
• Step wise marking is done during correction, so write all the required steps, always start with the formula for the numerical and specify the unit in the answer and attempt all questions.
Important Physics topics for CBSE board exam
1. Electric dipole, electricfield due to dipole on axial and equatorial position, torque acting on it in external electric field numerical based on it.
2. Gauss theorem – its statement and applications and numerical
3. Diagram of electric field and equipotential surface as given in NCERT, parallel plate capacitor with dielectric medium, energy of capacitor and numerical based on combination of capacitor.
4. Devices – Meter Bridge, Potentiometer, Cyclotron, moving coil galvanometer, transformer, ac generator and rectifier.
5. Working and uses of Zener diode, Photo diode, LED, and Solar cell.
6. Photoelectric equation, variation of photoelectric current with intensity and frequency, Debroglie wavelength for charged particles.
7. Bohrs postulates, hydrogen spectrum, radius, velocity and total energy of the electrons.
8. Law of radioactivity, half life, average life and binding energy curve.
9. Biotsavart law and its application for current loop on its axis, Amperes circuital law and its application for solenoid and toroid, comparison between dia, para and ferromagnetic material, terms like retentivity, coericivity, Lenz law and its application based question, self inductance of long solenoid and mutual inductance between two coils or solenoids, energy stored in inductor, LCR circuit and condition of resonance.
10. Derivation of refraction through spherical surface ,lens maker formula, prism formula, fringe width formula by YDS, condition for minima and maxima formation in single slit diffraction, image formation by compound microscope and telescope and their magnification .Reflecting type telescope and its comparison with refracting type.
Answer these question for revision
Q .1 a) Consider three charges q1, q2, q3 each equal to q at the vertices of an equilateral triangle of side l. What is the force on a charge Q (with the same sign as q) placed at the centroid of the triangle.
b) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
(c) Explain why two field lines never cross each other at any point?
Q.2 Using Bohr’s postulates of atomic model , derive expressions for the velocity of an electron in nth orbit of the hydrogen atom .
Q.3 Sketch the graph showing variation of stopping potential with the frequency of the incident radiation for two photosensitive materials 1 and 2 having threshold frequencies ν2>ν1.In which case is the stopping potential is more and why ?
Q.4 Discuss briefly refraction from rarer to denser medium at a convex spherical refracting surface when the image formed is real.
Prove that n_2/v-n_1/u=(n_2-n_1)/R
Q.5 Derive an expression for resistivity of a wire in terms of its material’s parameters, number density of free electrons and relaxation time.
Q.6 In a chamber, a uniform magnetic field of 6.5 G (1 G = 10–4 T) is maintained. An electron is shot into the field with a speed of 4.8 × 106 m s–1 normal to the field. Explain why the path of the electron is a circle. Determine the radius of the circular orbit. (e =1.5 × 10–19 C, me = 9.1×10–31 kg)
Q.7 Show diagrammatically the behaviour of magnetic field lines in the presence of (i) paramagnetic and (ii) diamagnetic substances (iii) ferromagnetic substance. How does one explain this distinguishing feature?
Q.8 An electric element X, when connected to an alternating voltage source has the voltage through it leading the current by π/2 rad .Identify X and draw the phasor diagram for it .Define its reactance and write an expression for its reactance. Draw graph showing variation of its reactance with frequency.
Q.9 A parallel plate capacitor of plate area A and separation d is charged to a potential V. The battery is then disconnected and a dielectric slab of thickness d and dielectric constant K is inserted in the capacitor. What change if any, will take place in
Charge on the plates.
Voltage across the capacitor.
Electric field between the plates.
Q.10 When a ray of light passes through a triangular glass prism, find out the relation for the total deviation, , in terms of the angle of incidence, i, and angle of emergence e. Plot a graph showing the variation of angle of deviation with the angle of incidence and obtain the condition for the angle of minimum deviation.
Q.11 Derive the expression for the law of radioactive decay of a given sample having initially N0 nuclei decaying to the number N present at any subsequent time t.
(i) Plot a graph showing the variation of the number of nuclei versus the time t lapsed.
(ii) Mark a point on the plot in terms of T1/ 2 value when the number present
N = N0//16.
Q.12. Draw a labelled diagram for image formation by refracting type Astronomical telescope. Hence obtain the magnification when the image is formed at infinity. Why reflecting type telescope is preferred over refracting type? (Give any two reasons.)
Q.13 Draw the circuit diagram of a full wave rectifier and explain its working. Also give its input and output waveform.
Q.14 Draw the intensity distribution pattern for the (i) the fringes produced in interference , and (ii) the diffraction bands produced due to a single slit.Write any one point of difference between the phenomena of interference and diffraction.
Q.15 (a) Derive the expression for the energy stored in the inductor and show that it depends on the strength of magnetic field.
(b) A circular coil of radius 10 cm, 500 turns and resistance 2 Ω is placed with its plane perpendicular to the horizontal component of the earth’s magnetic field. It is rotated about its vertical diameter through 180° in 0.25 s. Estimate the magnitudes of the emf and current induced in the coil.
Guiding students on how they can score well with an organised approach, Physics teacher Saroj Mishra gives important topics and essential questions to revise for board exams.
Physics New Exam Pattern
This exam pattern is changed. In the question Paper there are four sections. Section A contains objective type questions. It has 20 questions each of 1 marks. Under this category multiple choice questions and fill in the blanks are introduced for the first time, these will play vital role in the scoring of the students in the subject.
Section B and Section C contains 7 questions of 2 marks and 3 marks respectively. Section D contains 3 questions of 5 marks. There is no overall choice, however internal choice is provided in 2 questions of 1 mark, 2 questions of 2 marks, 1 question of 3 marks and all 3 questions of 5 marks.
Topic weightage
1. Electrostatics and current electricity: 16 marks.
2. Magnetic effects of current, magnetism, electromagnetic induction and alternating: 17 marks.
3. EM waves and Optics: 18marks.
4. Dual nature of matter and radiation, atoms and nuclei:12 marks
5. Electronic devices: 7 marks
How to prepare for Physics exam?
• Best way of preparing is practice the derivations, diagrams associated and the related numerical.
• Study thoroughly from NCERT book. You must study examples and the exercise given at the end.
• Solve 3 to 5 practice papers after completing the revision will give the confidence to the students as well the specific points which they need to remember.
• Do not bother yourself much if any particular question is not striking at that moment, proceed further later on you can get back to that question.
• Step wise marking is done during correction, so write all the required steps, always start with the formula for the numerical and specify the unit in the answer and attempt all questions.
Important Physics topics for CBSE board exam
1. Electric dipole, electricfield due to dipole on axial and equatorial position, torque acting on it in external electric field numerical based on it.
2. Gauss theorem – its statement and applications and numerical
3. Diagram of electric field and equipotential surface as given in NCERT, parallel plate capacitor with dielectric medium, energy of capacitor and numerical based on combination of capacitor.
4. Devices – Meter Bridge, Potentiometer, Cyclotron, moving coil galvanometer, transformer, ac generator and rectifier.
5. Working and uses of Zener diode, Photo diode, LED, and Solar cell.
6. Photoelectric equation, variation of photoelectric current with intensity and frequency, Debroglie wavelength for charged particles.
7. Bohrs postulates, hydrogen spectrum, radius, velocity and total energy of the electrons.
8. Law of radioactivity, half life, average life and binding energy curve.
9. Biotsavart law and its application for current loop on its axis, Amperes circuital law and its application for solenoid and toroid, comparison between dia, para and ferromagnetic material, terms like retentivity, coericivity, Lenz law and its application based question, self inductance of long solenoid and mutual inductance between two coils or solenoids, energy stored in inductor, LCR circuit and condition of resonance.
10. Derivation of refraction through spherical surface ,lens maker formula, prism formula, fringe width formula by YDS, condition for minima and maxima formation in single slit diffraction, image formation by compound microscope and telescope and their magnification .Reflecting type telescope and its comparison with refracting type.
Answer these question for revision
Q .1 a) Consider three charges q1, q2, q3 each equal to q at the vertices of an equilateral triangle of side l. What is the force on a charge Q (with the same sign as q) placed at the centroid of the triangle.
b) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
(c) Explain why two field lines never cross each other at any point?
Q.2 Using Bohr’s postulates of atomic model , derive expressions for the velocity of an electron in nth orbit of the hydrogen atom .
Q.3 Sketch the graph showing variation of stopping potential with the frequency of the incident radiation for two photosensitive materials 1 and 2 having threshold frequencies ν2>ν1.In which case is the stopping potential is more and why ?
Q.4 Discuss briefly refraction from rarer to denser medium at a convex spherical refracting surface when the image formed is real.
Prove that n_2/v-n_1/u=(n_2-n_1)/R
Q.5 Derive an expression for resistivity of a wire in terms of its material’s parameters, number density of free electrons and relaxation time.
Q.6 In a chamber, a uniform magnetic field of 6.5 G (1 G = 10–4 T) is maintained. An electron is shot into the field with a speed of 4.8 × 106 m s–1 normal to the field. Explain why the path of the electron is a circle. Determine the radius of the circular orbit. (e =1.5 × 10–19 C, me = 9.1×10–31 kg)
Q.7 Show diagrammatically the behaviour of magnetic field lines in the presence of (i) paramagnetic and (ii) diamagnetic substances (iii) ferromagnetic substance. How does one explain this distinguishing feature?
Q.8 An electric element X, when connected to an alternating voltage source has the voltage through it leading the current by π/2 rad .Identify X and draw the phasor diagram for it .Define its reactance and write an expression for its reactance. Draw graph showing variation of its reactance with frequency.
Q.9 A parallel plate capacitor of plate area A and separation d is charged to a potential V. The battery is then disconnected and a dielectric slab of thickness d and dielectric constant K is inserted in the capacitor. What change if any, will take place in
Charge on the plates.
Voltage across the capacitor.
Electric field between the plates.
Q.10 When a ray of light passes through a triangular glass prism, find out the relation for the total deviation, , in terms of the angle of incidence, i, and angle of emergence e. Plot a graph showing the variation of angle of deviation with the angle of incidence and obtain the condition for the angle of minimum deviation.
Q.11 Derive the expression for the law of radioactive decay of a given sample having initially N0 nuclei decaying to the number N present at any subsequent time t.
(i) Plot a graph showing the variation of the number of nuclei versus the time t lapsed.
(ii) Mark a point on the plot in terms of T1/ 2 value when the number present
N = N0//16.
Q.12. Draw a labelled diagram for image formation by refracting type Astronomical telescope. Hence obtain the magnification when the image is formed at infinity. Why reflecting type telescope is preferred over refracting type? (Give any two reasons.)
Q.13 Draw the circuit diagram of a full wave rectifier and explain its working. Also give its input and output waveform.
Q.14 Draw the intensity distribution pattern for the (i) the fringes produced in interference , and (ii) the diffraction bands produced due to a single slit.Write any one point of difference between the phenomena of interference and diffraction.
Q.15 (a) Derive the expression for the energy stored in the inductor and show that it depends on the strength of magnetic field.
(b) A circular coil of radius 10 cm, 500 turns and resistance 2 Ω is placed with its plane perpendicular to the horizontal component of the earth’s magnetic field. It is rotated about its vertical diameter through 180° in 0.25 s. Estimate the magnitudes of the emf and current induced in the coil.