CBSE 12TH PHYSICS - Online Test
Q1. Relation between ray and wave front is
Answer : Option D
Explaination / Solution:
Huygens’ construction tells us that the new wavefront is the forward envelope of the secondary waves. When the speed of light is independent of direction, the secondary waves are spherical. The rays are then perpendicular to the wavefronts.
Q2. magnetic potential energy Um of Compass needle of known magnetic moment m in a uniform magnetic field field is
Answer : Option D
Explaination / Solution:
No Explaination.
Q3. The total current in a semiconductor is
Answer : Option B
Explaination / Solution:
Electrons will experience a attractive force from the positive terminal, so they move towards the positive terminal of the battery by carrying the electric current.
Similarly holes will experience a attractive force from the negative terminal, so they moves towards the negative terminal of the battery by carrying the electric current.
Thus, in a semiconductor electric current is carried by both electrons and holes. In intrinsic semiconductor the number of free electrons in conduction band is equal to the number of holes in valence band.
The current caused by electrons and holes is equal in magnitude. The total current in intrinsic semiconductor is the sum of hole and electron current.
Total current = Electron current + Hole current I =
Q4. Plane electromagnetic waves are
Answer : Option B
Explaination / Solution:
No Explaination.
Q5. Coils and are stationary. connected in series with one very small diwali bulb while is connected to a battery .If the connection is suddenly snapped
Answer : Option D
Explaination / Solution:
Flux will be changed due to this current is induced momentarily
Q6. For a given frequency of light and a positive plate potential in the set up below, If the intensity of light is increased then
Answer : Option C
Explaination / Solution:
With increase in intensity no. of photon incident increases. So that more electron emitted from metal and photo current increases with increase in intensity.
Q7. Which of these is an acoustic transducer?
Answer : Option D
Explaination / Solution:
Acoustic transducer is a device which converts one form of signal into another without any direct contact.
Q8. Ionization of a neutral atom is the
Answer : Option A
Explaination / Solution:
It is not possible to remove or add protons to atom, but electron can be added or removed by an atom easily so charge can be developed on an atom by removing or adding electrons, by adding electrons it becomes negative charged ,by removing electrons it becomes positive charged.
Q9. The model that best explains the results of Geiger-Marsden experiment is
Answer : Option D
Explaination / Solution:
No Explaination.
Q10. Average power supplied to a capacitor over one complete cycle
Answer : Option D
Explaination / Solution:
We know that in capacitor Current leads Voltage by 90degree. Over one complete cycle, in first quarter cycle Capacitor charges and next quarter cycle it's discharge. This will continue in next negative half cycle. So the NET POWER ABSORB IS ZERO.
