Top 10 Questions in Physics CBSE Class 12 Exam - 2020
CBSE Class 12 Physics exam is one of the most crucial exams and it is important for students who want to pursue engineering. Check top 10 important physics questions and answers that will help you plan your study and revision.
Physics is a tough nut to crack for CBSE Class 12 students. It is not only important for entrance exam purposes but is also a scoring subject. Understanding the formulae of Physics and answering the questions correctly can easily help you score. So, it is important that you know the chapters/topics that are asked regularly.
Important Questions & Answers CBSE Class 12 Board Exam 2020 : Physics
1. State Biot–Savart law. Use it to obtain the magnetic field at an axial point at a distance x from the centre of a circular coil of radius carrying a current I. Compare the magnitude of the magnetic field at the centre of the coil and at an axial point for which
Answer - According to the Biot–Savart law, the magnetic field dB due to an element dl carrying a steady current I at a point P at a distance r from the current element is
By taking a circuit element, we can write the magnetic field due to this segment. Then integrate to find the magnetic field due to the circular current loop, which comes out to be
2. Distinguish between the magnetic properties of paramagnetic, diamagnetic and ferromagnetic substances in terms of
Give one example of each of these materials. Draw magnetic field lines near a diamagnetic and paramagnetic substance.
3. (i) Each free electron accelerates due to the force that acts on it. This increases its drift speed until it collides with a positive ion of the metal. It loses some energy after each collision, but it again accelerates and then collides and once again loses some energy. This sequence of events continues. Hence, on an average, the electrons acquire only a drift speed, but they are not able to accelerate.
(ii)In the presence of an electric field, the path of the electrons is generally curved rather than straight.
4. What type of a charge is present on an n-type semiconductor? Why?
5. An electron, alpha particle and proton have the same kinetic energy. Which of these particles has the shortest de Broglie wavelength?
6. Explain how the maximum kinetic energy of electrons emitted from a metal surface varies with the frequency of incident radiation.
7. Two dielectric slabs of dielectric constants K1 and K2 and of equal width are filled in between two plates, each of area A, of a parallel plate capacitor. How does the capacitance of the capacitor get affected?
8. Derive lens maker’s formula for a double convex lens.
9. How does the size of a nucleus depend on its mass number? Explain why the density of nuclear matter is independent of the size of a nucleus.
10. The given graph shows variation of charge q versus potential difference V for capacitors. The two capacitors have same plate separation. However, the plate area of is double that of. Which of the lines in the graph correspond to and why?
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