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

The more luminous they are, the more reactions are taking place in their cores. Massive stars live shorter lives than the common small stars because even though they have a larger amount of hydrogen for nuclear reactions, their rate of consuming their fuel is very much greater.

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is it right?magnetic field lines form closed loop

Posted by ▪▪Amrit▪▪ ❤ 6 years, 3 months ago

CBSE > Class 12 > Physics

4 answers

Kajal Kunwar 6 years, 3 months ago

Yes its right

1Thank You

Anisha Sharma 6 years, 3 months ago

yes it is right.... magnetic field lines form closed loops

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Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

yes magnetic field lines form close loop reason behind is that magnetic pole always exist in pairs. so magnetic lines of force run from N-pole to s-pole outside the magnet and from S-pole to N-pole inside the magnet. they do not start or end anywhere and hence always form close loop .

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Aman Kumar 6 years, 3 months ago

Yes , it is right

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Four charges +q,+q,-q,-q are placed reapectively at the four corner A,B,C,D of a square a side'a'. calculate the electic field at the center of square???

Posted by Anjali Sankwar 6 years, 3 months ago

CBSE > Class 12 > Physics

2 answers

Anjali Sankwar 6 years, 3 months ago

Kese solve kiya tha kya

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Deepak Gautam 6 years, 3 months ago

I think it is 0

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ANSWER

Do stars have gravity?

Posted by Anish Rai 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

yes stars have gravity infact approx each and every body in the universe have some gravity no matter whether it is more or less. never forget every body which have mass posses some gravity.

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Why can one ignore quantization of charge when dealing with macroscopic charges?

Posted by Surendra Prasad 6 years, 3 months ago

CBSE > Class 12 > Physics

3 answers

Ayush Singh 6 years, 3 months ago

Quantization of charges is only applicable for small calcutions as charge present in huge quantity so for calculating large quantity we use CONTINUOS CHARGE DISTRIBUTION

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Yogita Ingle 6 years, 3 months ago

In macroscopic or large scale charges, the charges used are huge as compared to the magnitude of electric charge. Hence, quantization of electric charge is of no use on macroscopic scale. Therefore, it is ignored and it is considered that electric charge is continuous.An electrostatic field line is a continuous curve because a charge experiences a continuous force when traced in an electrostatic field.The field cannot have sudden breaks becaus ethe charge moves continuously and does not jump from one point to another.

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꧁≪Mämƭå ℭℏ۝ᑌĎℎàℜÿ? 6 years, 3 months ago

Yes ,we can ignore quantization of charge on macromolecules as quantization of charge is only for small charges as electrons.

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What is the construction and working principle of ven-de-graff generator

Posted by Chayanika Deka 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Sia ? 6 years, 3 months ago

AC generator is based upon Fleming's right hand rule.

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Is optics has been removed from class 12th syllabus or not

Posted by Ashna Mehta 6 years, 3 months ago

CBSE > Class 12 > Physics

2 answers

Priya Dharshini 6 years, 3 months ago

It is there in syllabus..

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Abhiyank Rajouria 6 years, 3 months ago

No , it is included in the syllabus.

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ANSWER

What can be the topic for investegatory project

Posted by Akshita Vaish 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Abhiyank Rajouria 6 years, 3 months ago

Hi Akshita , You can check them out in CBSE Syllabus Section (Physics) and on scrolling down , you will get some suggested investigatory projects .

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ANSWER

Why do electrostatic feild lines not form close loops?

Posted by Shreyosee Sarkar 6 years, 3 months ago

CBSE > Class 12 > Physics

2 answers

Yogita Ingle 6 years, 3 months ago

Electric charges can exists as monopole or positive or negative charges exists independently thus the lines originate from the charges and eventually fades at infinity.

Electric field lines flow from positive to negative charge thus never come back to the positive charge. Therefore they do not form a closed loop. This can be considered as a straight one way road.Whereas magnetic lines form closed loops because they come back at the same pole from which they originate.

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Vidit Kushwaha 6 years, 3 months ago

Because they do not intersect each other

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ANSWER

What is a rectifier and it's construction?

Posted by Gayatri Kumari 6 years, 3 months ago

CBSE > Class 12 > Physics

0 answers

ANSWER

Really cbse mei 20 mcq aane wala hei 2020 ka exam mei pls tell me

Posted by Erasmus Gaurav 6 years, 3 months ago

CBSE > Class 12 > Physics

7 answers

Aman Kumar 6 years, 3 months ago

Kya mai tumse ek suggestion mang sakta hu...

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Aman Kumar 6 years, 3 months ago

Priya , tumhara chemistry mai kitna chapter ho gya...

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Priya Dharshini 6 years, 3 months ago

It is said objective questions... and not truly only mcq... it can be fillups,1 marks give reasons and mcq also... need to wait still sample paper arrives..

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Anisha Sharma 6 years, 3 months ago

Haan

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꧁≪Mämƭå ℭℏ۝ᑌĎℎàℜÿ? 6 years, 3 months ago

Yes....any doubt... For sure aane wale hai??

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Abhay Gupta 6 years, 3 months ago

Haa aane wale hai

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Aditi Pandey 6 years, 3 months ago

yes

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ANSWER

Drift velocity kya hota hai

Posted by Manish Patel 6 years, 3 months ago

CBSE > Class 12 > Physics

3 answers

Ayush Singh 6 years, 3 months ago

It is the velocity obtained by the current carriers or charged particles

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Aditi Pandey 6 years, 3 months ago

it is the average velocity attained by charged particles, such as electrons in a material due to electric field.

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Nasima Khan 6 years, 3 months ago

Velocity of charged particle between two successive collision known as drift Velocity

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A potential difference of 4.5V is applied across a conductor of length 0.1 m. If the drift velocity of electrons is 1.5 × 10−4 ?/?, find the electron mobility

Posted by Shivam Yadav 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Ayush Singh 6 years, 3 months ago

Brother just calculate electric field with the help of this formula E=V/L Aand then use this formula :- mobility=drift velocity/electric field

5Thank You

ANSWER

The intensity of X-rays decreases exponentially according to the law I=I0 e-kx, where I0 is the initial intensity of X-rays and I is the intensity after it penetrates a distance x through lead. If k be the absorption coefficient, then find the dimensional formula for it.

Posted by Akash Tomar 6 years, 3 months ago

CBSE > Class 12 > Physics

0 answers

ANSWER

Limitations of coulomb's law

Posted by Anubhuti Khatri 6 years, 3 months ago

CBSE > Class 12 > Physics

4 answers

Deepak Jindal 6 years, 3 months ago

Only valid for point charge????

1Thank You

S.....Sharma☺??? .. 6 years, 3 months ago

Coulomb force is only valid for point charge

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S.....Sharma☺??? .. 6 years, 3 months ago

And also valid for one charge is moving and second charge in rest

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Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

coulomb's law is valid only for point charges.

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ANSWER

When CBSE is gonna release their sample paper?

Posted by Justin Bieber 6 years, 3 months ago

CBSE > Class 12 > Physics

3 answers

Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

yup

1Thank You

Justin Bieber 6 years, 3 months ago

Hmm solved papers na?

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Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

cbse officially release it mid September and October. but bahut late ho jayega uss se accha hai aap Arihant le lo 5 years question vo v contain karte hai

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ANSWER

What is the theory of ven-de-graff generation?

Posted by Chayanika Deka 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Ďãřşháñăã Yadav ? ? ? ✊ 6 years, 3 months ago

it is an electrostatic generator capable of building up high potential difference of the oder of 10^7 volts.

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Two charged particles are placed at a distance of 1cm apart. What is the minimum possible magnitude of the electric force acting on each charge ?...pls answer

Posted by Aditya Kumar 6 years, 3 months ago

CBSE > Class 12 > Physics

2 answers

Abhishek Bonal 6 years, 3 months ago

The optimum distance to follow coulomb's law is 10raise to power-15

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Annat Jaiswal 6 years, 3 months ago

Kq1q2

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ANSWER

Calculate de - Broglie wavelength of an electron

Posted by Deep Singh 6 years, 3 months ago

CBSE > Class 12 > Physics

0 answers

ANSWER

Frnds investigatory projects hand written hone chahiye ya printed aap sab kese karoge

Posted by Abhishek Bhardwaj 6 years, 3 months ago

CBSE > Class 12 > Physics

7 answers

Srishti Choudhary ✍⏳ 6 years, 3 months ago

Ur most welcome mr aman..?

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Priya Dharshini 6 years, 3 months ago

U need to ask ur school teacher.... in our school everything need to be printed no hand written...

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Aman Kumar 6 years, 3 months ago

Thanks srishti.....BTW hand written is also nice

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▪▪Amrit▪▪ ❤ 6 years, 3 months ago

accord8ng to my teacher handwritten will be more attractive

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Srishti Choudhary ✍⏳ 6 years, 3 months ago

Aman shi keh rha h ye apne subject teacher s hi puchho

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Srishti Choudhary ✍⏳ 6 years, 3 months ago

Hmare toh sb kuch hand written hoga

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Aman Kumar 6 years, 3 months ago

It depend on ur school...ask it about ur subject teacher what they want .....hume kaha gya hai ki starting ke index , cetificate, acknowledgement ,etc...ye sab printed ho sakta hai but the main experiment should be hand written...

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ANSWER

Cbse exam new paper style 2019-20

Posted by Simardeep Singh 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Simardeep Singh 6 years, 3 months ago

Cbse exam style paper 2019-20

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ANSWER

A Helium nucleus completes one round of a circle of radius 0.8 m in 2s . Find the magnetic field at the center of the circle

Posted by Vaibhav Porwal 6 years, 3 months ago

CBSE > Class 12 > Physics

1 answers

Annat Jaiswal 6 years, 3 months ago

By using the formula B=m.i/2 r

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ANSWER

Figure (32-E2) shows an arrangement to measure the enmf E and internal resistance r of a battery.The voltmeter has a very high resistance and the ammeter also has some resistance.The voltmeter reads 1.52 V when the switch S is open.When the switch is closed the voltmeter reading drops to 1. 45 V and the ammeter reads 1.0 A. Find the emf and the internal resistance of the battery.

Posted by Karan Barmase 6 years, 3 months ago

CBSE > Class 12 > Physics

3 answers

Srishti Choudhary ✍⏳ 6 years, 3 months ago

Yes btao plzz

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Swati Singh 6 years, 3 months ago

Tell me one thing,how do u able attach these photos in yr ans??????

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Gaurav Seth 6 years, 3 months ago

a) When switch is open, no current passes through the ammeter. In the upper part of the circuit the Voltmenter has ∞ resistance. Thus current in it is 0.

Voltmeter read the emf. (There is not Pot. Drop across the resistor).

b) When switch is closed current passes through the circuit and if its value of i.

The voltmeter reads