CBSE Guess > Papers > Important Questions > Class XII > 2013 > Physics > Physics - by Mr. Raghu Sharma
CBSE CLASS XII
Physics
- Force is given by F = Q (VxB). Of these, Name the Pairs of vectors which are always at right angles to each other.
- Mention one advantage and one disadvantage of AC over DC.
- Name two electro magnetic waves that are emitted by an incandescent bulb.
- Mention one advantage of reflecting type telescope.
- With what purpose was famouse Davisson- Germer experiment with electrons performed?
- Draw the symbol of the universal logic gate.
- Draw energy band diagram of P-type semiconductor.
- Capacitor P, Q and R each have a capacitance ‘C’. A battery can charge the capacitor P to a potential V. If after charging P, the battery is disconnected from it and the charged capacitor P is connected in following separate instances to Q and R
- In parallel to Q and
- In series to ‘R’
- A metal wire is stretched to increase its length by 10% What is the percentage change in its resistance? Will the resistivity of the wire change?
- When a battery of emf. ‘E’ and internal resistance ‘r’ is connected to a resistance ‘R’, a current I flows through it. Derive a relation between E, I, r and R.
- Mention 2 properties of alloys from which permanent magnets are made.
- An inductor of 2mH carries a current of 5A. The direction of current is reversed in it in half a second due to which a voltage is produced across the inductor. What is this phenomenon known as? Find the Voltage Produced.
- Plot a graph to show how the following quantities vary with the frequency of the source.
- Capacitive reactance
- Inductive reactance.
- Vehicles moving in foggy weather use yellow color headlights. Why?
- Give reasons for :
- The sky appears blue
- Sun appears reddish at sunset and sunrise.
- Draw a labeled block diagram for a communication system.
- Define electric field intensity at a point. Derive an expression for the electric field intensity at a point on the axial line of a short dipole.
- Show that the potential on the equatorial line of an electric dipole is zero
- What is an electric dipole? Derive an expression for the torque acting on an electric dipole, when held in a uniform electric field. Hence, define the dipole moment.
- State Gauss theorem in electrostatics. Using this theorem, derive an expression for the electric field
- intensity due to an infinite plane sheet of charge of charge density σ
- Show mathematically that for any point out side the shell, the field due to a uniformly charged thin
- spherical shell is the same as if the entire charge of the shell is concentrated at the centre.
- Apply gauss theorem to find electric field intensity at a point due to an infinitely long thin, uniformly
- charged straight wire.
- Define the capacitance of a capacitor. Give its S.I unit for a parallel plate capacitor, prove that the total
- energy stored in a capacitor is ½ cv2 and hence derive expression for the energy density of the capacitor.
- Derive an expression for the capacitance of a parallel plate capacitor when the space between the plates is partially filled with a dielectric medium of dielectric constant k.
- In a hydrogen atom, an electron revolves around a proton. Which of these two exerts a greater electrostatic force on the other?
- What is the force experienced by a positively charges particle Q moving at right angles to a uniform electric field E.
- What is the order of voltages that can be built up using a Van De Graff generator?
- What is the angle b/w Electric field and Dipole moment at an axial point?
- Define gyromagnetic ratio. What is it’s value?
- State the condition in which terminal voltage across a secondary cell is equal to its emf.
- The dielectric strength of air is 3 x 106 V/m. What is the maximum charge that can be safely stored on a sphere of radius 10m?
Submitted By : Mr. Raghu Sharma
Email: [email protected]
