CBSE 12TH PHYSICS - Online Test
Q1. The propagation of light is best described by,
Answer : Option D
Explaination / Solution:
No Explaination.
Q2. Which of the following statements about bar magnets is correct ?
Answer : Option D
Explaination / Solution:
As magnetic monopole does not exist. If we split the bar magnet into two pieces each part will have its own north and south pole.
Q3. In the case of metals the valence and conduction bands have
Answer : Option C
Explaination / Solution:
The materials can be classified by the energy gap between their valence band and the conduction band. The valence band is the band consisting of the valence electron, and the conduction band remains empty. Conduction takes place when an electron jumps from valence band to conduction band and the gap between these two bands is forbidden energy gap. Wider the gap between the valence and conduction bands, higher the energy it requires for shifting an electron from valence band to the conduction band.
- In the case of conductors, this energy gap is absent or in other words conduction band, and valence band overlaps each other. Thus, electron requires minimum energy to jump from valence band. The typical examples of conductors are Silver, Copper, and Aluminium.
- In insulators, this gap is vast. Therefore, it requires a significant amount of energy to shift an electron from valence to conduction band. Thus, insulators are poor conductors of electricity. Mica and Ceramic are the well-known examples of insulation material.
- Semiconductors, on the other hand, have an energy gap which is in between that of conductors and insulators. This gap is typically more or less 1 eV, and thus, one electron requires energy more than conductors but less than insulators for shifting valence band to conduction band.
Q4. Maxwell’s displacement current is a response to
Answer : Option C
Explaination / Solution:
No Explaination.
Q5. When a bar magnet is pushed towards the coil connected in series with a galvanometer, the pointer in the galvanometer G
Answer : Option B
Explaination / Solution:
When bar is in motion then flux will changed hence current will be induced.
Q6. In which case is electron emission from a metal not known?
Answer : Option A
Explaination / Solution:
No Explaination.
Q7. The three elements of a generalized communication system are
Answer : Option A
Explaination / Solution:
In communication the Transmitter helps in transmitting the signal through communication channel which acts as a physical path that connects transmitter to a receiver.And the receiver receives the transmitted signal and converts those signals in their original form.
Q8. If electrons move out of a body to another body every second, how much time is approximately required to get a total charge of 1 C on the other body?
Answer : Option A
Explaination / Solution:
We know that 1 Coulomb = 6.242×1018 eletrons
given 109 electrons take 1 secs
=> 109 electrons ------> 1 sec
=> 1 electrons ---------> secs
=> 6.242×1018 ------>
= 6.242×109 secs = years
=197.93 years= 200 years approx
Q9. Each element is associated with
Answer : Option D
Explaination / Solution:
No Explaination.
Q10. The main reason for preferring usage of AC voltage over DC voltage
Answer : Option D
Explaination / Solution:
By using the phenomenon of mutual induction, transformers allow us to easily change voltage of AC. This is necessary to cut down poer losses while supplying electricity to our homes
