CBSE Class 12th Physics Question Paper, Physics Sample Paper 2024
1) Define electric dipole and dipole moment.
Ans:- An electric dipole is a pair of equal and opposite point charges q and -q, separated by distance 2a.
and the dipole moment vector p of an electric dipole is defined by p =q×2ap.
2) Can the potential difference across a battery be greater than ita e.m.f?:
Ans:- Normally not, But during the charging when the battery is connected to the external source,the terminal potential difference V is greater than I.e.
3) Why is the terminal voltage across a battery more than the e.m.f during recharging?
Ans:- During recharging of the battery,the voltage across the internal resistance (= Ir) and the e.m.f are in the same direction,hence they get added up,to give terminal voltage.So the terminal voltage is greater than the e.m.f.
12th Physics Question Paper
4) What is the difference between an electromagnet and a permanent magnet? How is an electromagnet deigned? State any two factors on which te strength of an electromagnet depend.
Ans:- A permanent magnet is an object made from material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door.
An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current passes.
Design of electromagnet: An electromagnet is made
a coil of wire wrapped on a soft iron core which acts as a magnet when an electric current passes through it, but stops being a magnet when the current stops.
Following factors affecting the strength of Electro- magnet:
(i) the number of windings in the electromagnet.
(ii) the amount of current supplied.
12th Physics Question Paper
5) What is the frequency of domestic alternating current supply? How many times does it become zero in one second?
Ans:- The frequency of domestic ac supply is 50 Hz. It becomes zero twice in each chle and so it becomes zero 100 times per second.
6) Explain huygen’s principle for propagation of a wave front.
Ans:- 10. According to Huygen’s principle for propagation of wavefront will be along all directions. All the points where wave reach at same time is called wavefronts, Propogation of wavefront stablished on the following two assumptions:
(i) Each point on a wavefront acts as a fresh source of disturbance.
(ii) The new wavefront of any later time is obtained by taking the forward taking REDMI NOTE 5 PRO envelope of the secondary wavelets me.
7) State two factors by which the range of transmission of signals by a T.V tower can be increased.
Ans:- (I) By increasing the height of the tower
(ii) By increasing the height of the receive antenna, so that it may directly intercept the signal from the transmitting antenna.
8) State some application of x-rays?
Ans :- (i) They are used in radiotherapy to treat tumours and cancer.
(ii) They (soft g-rays) are used to kill micro organisms in food industry so as to preserve food stuffs for a longer time.
(iii) They are used to produce nuclear reactions.
12th Physics Question Paper
9) Define mutual induction?
Ans:- It is defined as the process of producing induced e.m.f in a coil by changing the current or magnetic flux linked with the neighbouring coil.
10) Why the inductance coils are made of Cooper?
Ans :- The inductance coils made of Cooper have very small ohmic resistance.Due to change in magnetic flux,a large induced current will be produced in such an inductance and it offers appreciable opposition to the flow of current due to the applied e.m.f.
10) Explain Electrical Resonance.
Ans-The phenomenon of resonance occurs in those systems which have a tendency to oscillate at a particular frequency known as natural frequency of oscillation of the system. When such type of a system is driven by such a periodic energy source whose frequency is equal to the natural frequency of the system, then the amplitude of oscillation becomes maximum and resonance is said to occur. For example, a swinging child has a natural frequency of oscillation. If another child pushes the swinging child at regular intervals such that frequency of the pushes is nearly the same as the natural frequency of oscillation, then the amplitude of oscillation of the child becomes maximum,Thus resonance has occurred.
12) How can you distinguish between an unpolarized light and a linearly polarised light beam using a Polaroid?
Ans:- The given beam of light is made incident on a polaroid and the polaroid is rotated slowly and the intensity of transmitted beam is observed. If there is no variation in intensity, the given beam is unpolarised, but if the intensity varies with minimum intensity zero twice in a rotation, the given beam is linearly polarised .
13) Mention some property some properties of x-rays?
Ans:-(i) They can undergo reflection, refraction, interference diffraction and polarisation.
(ii) they affect photo graphic plates.
(iii) They cast shadows of the objects falling in their path due to the reason that they travel in a straight line.
(iv) They can penetrate the materials that are opaque to visible or UV light.
(v) They can cause photoelectric effect.
(vi) They can cause flourescence in certain materials like zinc sulhide, calcium tungstate etc.
(vii) They ionise the gas through which they pass.
(viii) They produce secondary X-rays when fall on certain metals. They secondary X-rays are accompanied by fast moving electrons.
(ix) They are em. waves of very short wavelength and thus earth’s atmosphere opaque for X-rays.
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