CBSE > Class 12 > Physics | CBSE Board | Homework Help

A Zener diode is a heavily doped silicon crystal diode which allows current to flow in the forward direction in the same manner as an ideal diode. It also permits the current to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage. Breakdown voltage is also known as Zener knee voltage.

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Anuj Sharma 7 years, 1 month ago

Zener diode is a P-N JUNCTION diode which is heavily doped on both sides and used in reverse bias state

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Project on electricity

Posted by Ram Babu Prajapati 7 years, 1 month ago

CBSE > Class 12 > Physics

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Using the bohr's model, calculate the speed of the electron in a H-atom in the n=1,2and3 levels. Plzz solve itt

Posted by Abhishek Rai 7 years, 1 month ago

CBSE > Class 12 > Physics

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What is space wave propagation

Posted by Bharti Bharti 7 years, 1 month ago

CBSE > Class 12 > Physics

2 answers

Yogita Ingle 7 years, 1 month ago

A space wave travels in a straight line from transmitting antenna to the receiving antenna. Space waves are used for line-of-sight (LOS) communication as well as satellite communication. At frequencies >50 MHz, communication is essentially limited to line-of-sight paths because waves cannot travel along earths surface as they get absorbed by earth, so propagation cannot be like ground wave propagation. Likewise propagation cannot be like sky waves as they are not reflected by ionosphere.
At these frequencies, the antennas are relatively smaller and can be placed at heights of many wavelengths above the ground. Because of line-of-sight nature of propagation, direct waves get blocked at some point by the curvature of the earth. If the signal is to be received beyond the horizon then the receiving antenna must be high enough to intercept the line-of-sight waves.

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Anuj Sharma 7 years, 1 month ago

It is a mode of transmission of signals having frequency >2 MHZ using reflection through troposphere

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Distinguish between a transducer and a repeater

Posted by Bharti Bharti 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Yogita Ingle 7 years, 1 month ago

Transducer is a device used for converting one form of energy into another form. Microphone is a transducer because it converts sound energy into electrical energy.
Repeater is a device which picks up electromagnetic signal, amplifies it and then again transmits it to the receiver. It is used when transmitted signal is attenuated beyond a certain limit or distance between a transmitter and a receiver is very large.It is used in the communication system.

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three characterstic feature in photoelectric effect which cannot be ecplained on the basis of wave theory of light but can be explained only using einstein equation?

Posted by Suman Rani 7 years, 1 month ago

CBSE > Class 12 > Physics

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Name the phenomenon which shows the quantum nature of electromagnetic radiation

Posted by Sandeep Kumar 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Gaurav Seth 7 years, 1 month ago

The phenomena showing quantum nature of electromagnetic radiations is Photoelectric effect.

It is a effect when electron is emitted when light shines on a material. Such electrons are called photo electrons.

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Kirchoff law

Posted by Abhay Jha 7 years, 1 month ago

CBSE > Class 12 > Physics

2 answers

Raunak Himmatramka 7 years, 1 month ago

It is simply energy conservation.

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Pragya Gupta 7 years, 1 month ago

Current and voltag

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Importance of coil in a galvanometer

Posted by Tanu Yadav 7 years, 1 month ago

CBSE > Class 12 > Physics

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Chainging galvanometer into voltmeter

Posted by Binay Gandhi 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Ritik Kushwaha 7 years, 1 month ago

By connecting high resistsnce to sereis to the coil. R=v/Ig- G

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Is doppler effect there in our syllabus ??????

Posted by Rupali Agrawal 7 years, 1 month ago

CBSE > Class 12 > Physics

2 answers

Vikas Goyal 7 years, 1 month ago

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Aman Pandey 7 years, 1 month ago

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krichhoff rule

Posted by Abhinav Singh Narayan 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Manish Barwa 7 years, 1 month ago

There are two rule of Kirchoff are followed: (1)the Kirchoff first law is also known as KCL law it is also known as junction rule. So junction rule is-at any junction of current element the sum of currents entering the junction must equal the sum of current leaving it. (2)-The Kirchoff second law is also known as KVL law It is also known as Loop rule-In a closed loop the algebraic sum of the emf is equal to the algebric sum of the product of resistance and the respective current them..

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In physics board exam 2019 class 12th Derivation will involve or not

Posted by Abhishek Rai 7 years, 1 month ago

CBSE > Class 12 > Physics

4 answers

Akshat Mishra 7 years, 1 month ago

Yes, derivation will involve

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Abhishek Rai 7 years, 1 month ago

2019 in sample paper 1or 2 derivation involve

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Kuldeep ?? 7 years, 1 month ago

Yes derivation are also important.if you do only derivation and theory you can score better.numerical come only of 15 marks.

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Priyanka P 7 years, 1 month ago

Only 1-2 derivation will involve

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How to solve questions of combination of plano cinex and concave lens...

Posted by Aman Goyal 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Akshat Mishra 7 years, 1 month ago

For concave lens formula (m=v/u=f-v/f =f/f+u)

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what are the suitable models for physics

Posted by Shashikala Pandey 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Sneha Bansal 7 years, 1 month ago

Suitable models for physics are from semiconductor and electronics eg. LED.,rectifier ...

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Write the expression for speed of electromagnetic waves in a medium of electrical permittivity E and magnetic permeability u

Posted by Aman Teotia 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Manish Rawat 7 years, 1 month ago

c=1\√u(not)×e(not)

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What is SI unit of charge?

Posted by Chandrakant Lolasure 7 years, 1 month ago

CBSE > Class 12 > Physics

3 answers

Suraj Upadhyay 7 years, 1 month ago

Coulomb is right

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Hema Bisht 7 years, 1 month ago

It isnot Coulamb its Coulomb (C)

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Akarsh Kumar 7 years, 1 month ago

Coulamb

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Why are the NAND and NOR gates called digital building gates

Posted by Krishna Soni 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Akarsh Kumar 7 years, 1 month ago

Because it is possible to make all types of other gatesv

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What is pole strength

Posted by Mahi Jain 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Yogita Ingle 7 years, 1 month ago

The pole strength will be the strength of each pole means the capacity of each pole ( north and south pole ) to attract any ferromagnetic substances and magnetic moment will be when u will multiply the pole strength with the length of the magnet .
So, on a typical magnet
pole strength = m
magnetic moment = m * l = ml

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two electric field lines can never intersect each other.Why?

Posted by Roshan Oraon 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Mukul Rana 7 years, 1 month ago

Because if they do so then there will be two direction of electric field at the same point Which is not possible

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Ampere circutal law

Posted by Aniket Kumar 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Mohhd Arkam 7 years, 1 month ago

The line integral of magnetic field through any closed loop is equal to mu nod times the net current i threading through the area enclosed by the loop

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Which type of current flows without moving of charges???

Posted by Chitra Bisht 7 years, 1 month ago

CBSE > Class 12 > Physics

2 answers

Sunny Dedha 7 years, 1 month ago

Displacement current

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Aman Jakhar 7 years, 1 month ago

An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma).

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Why photodiode are connected in reverse biase?

Posted by Ravendra Mishra 7 years, 1 month ago

CBSE > Class 12 > Physics

1 answers

Aditi Raj 7 years, 1 month ago

The fractional change due to incident light on minority charge carroers in reverse biasis much more than that over the majority charge carriers in forward bias. Thus, charge in reverse bias current is more easily measurable. So, photodiodes are used to measure the intensity im reverse bias condition.

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Weightage of ray optics..?

Posted by Meedha Wadhwa 7 years, 1 month ago

CBSE > Class 12 > Physics