# CBSE 12TH PHYSICS (Test 1)

Tag: cbse 12th physics
Q.1
Electronic communication refers to
A. transfer of information encoded in electrical signals
B. transfer of information or messages encoded in electrical signals
C. transfer of electricity from one point to another
D. transfer of messages encoded in electrical signals
Answer : Option B
Explaination / Solution:

When information are sent from one point to the other it has to be converted into electrical signal using transducer.The receiver receives it in its original from using receiver.Such from of communication is called electronic communication.

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Q.2
Any physical quantity like temperature can be converted to
A. Analog or digital electrical signal
B. only analog electrical signal
C. constant electrical voltage
D. only digital electrical signal
Answer : Option A
Explaination / Solution:

An electrical transducer is a device which is capable of converting the physical quantity into a proportional electrical quantity such as voltage or electric current. Hence it converts any quantity to be measured into usable electrical signal. This physical quantity which is to be measured can be pressure, level, temperature, displacement etc. The output which is obtained from the transducer is in the electrical form and is equivalent to the measured quantity. For example, a temprature transducer will convert temperature to an equivalent electrical potential. This output signal can be used to control the physical quantity or display it.moreover this is of two type Digital or Analog electrical signals.

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Q.3
Bandwidth of an electronic communication system
A. is the minimum frequency at which an equipment
B. is the maximum frequency at which an equipment
C. is the frequency range over which an equipment operates or the portion of the spectrum occupied by the signal
D. is number of bands in the spectrum
Answer : Option C
Explaination / Solution:

A range within a band of wavelengths, frequencies, or energies; especially : a range of radio frequencies which is occupied by a modulated carrier wave, which is assigned to a service, or over which a device can operate.

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Q.4
for a signal to be reproduced without distortion
A. All the harmonics should be present
B. none of these
C. only the fundamental is required
D. only the fundamental and first harmonic is required
Answer : Option A
Explaination / Solution:
No Explaination.

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Q.5
To increase the range of line of sight communication
A. decrease the height of transmitting tower only
B. increase the height of both transmitting and receiving towers
C. decrease the height of both transmitting and receiving towers
D. decrease the height of receiving tower only
Answer : Option B
Explaination / Solution:
No Explaination.

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Q.6
Basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc are
A. Semiconductors
B. metals
C. insulators
D. conductors
Answer : Option A
Explaination / Solution:

Semiconductors are materials that have electrical conductivity between conductors such as most metals and nonconductors or insulators like ceramics. Semiconductor material is used in the manufacturing of electrical components and used in electronic devices such as transistors and diodes. Semiconductors are the basic materials used in the present solid state electronic devices like diode, transistor, ICs etc

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Q.7
in n-type semiconductor majority carriers and minority carriers are respectively
A. germanium and silicon
B. electrons and holes
C. aluminum and boron
D. holes and electrons
Answer : Option B
Explaination / Solution:

N-type semiconductors have a larger electron concentration than hole concentration. The term n-type comes from the negative charge of the electron. In n-type semiconductors, electrons are the majority carriers and holes are the minority carriers. N-type semiconductors are created by doping an intrinsic semiconductor with donor impurities (or doping a p-type semiconductor as done in the making of CMOS chips). A common dopant for n-type silicon is phosphorus.

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Q.8
In an insulator, the forbidden energy gap between the valance band and conduction band is of the order of
A. 1 eV
B. > 5 eV
C. 2 MeV
D. eV
Answer : Option B
Explaination / Solution:

In an insulator, the forbidden energy gap is very large.In general, the forbidden energy gap is more than 5eV and almost no electrons are available for conduction. Therefore, a very large amount of energy must be supplied to a valence electron to enable it to move to the conduction band. In the case of materials like glass, the valence band is completely filled at 0 K. The energy gap between valence band and conduction band is of the order of 10 eV. Even in the presence of high electric field, the electrons cannot move from valence band to conduction band.

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Q.9
The conductivity of P – type semiconductor is due to
A. holes
B. electrons
C. none of the above.
D. both electrons and holes
Answer : Option A
Explaination / Solution:
No Explaination.

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Q.10
For forward biasing a P-N junction the positive terminal of the battery is connected to
A. N – type crystal
B. Neither P – type nor N – type crystal
C. P – type crystal
D. Either P –type or N – type crystal
Answer : Option C
Explaination / Solution:

Biasing is the application of a voltage across a p–n junction.

When we connect p-type region of a junction with the positive terminal of a voltage source and n-type region with the negative terminal of the voltage source, then the junction is said to be forward biased.

At this condition, due to the attraction of positive terminal of source, electrons which participated in covalent bond creations in p-type material, will be attracted towards the terminal.

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