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89 - Electricity Questions Answers

Physics >> Electricity >> Capacitors Medical Exam

a II plate capacitor has an electric field of 105 V/m b/w d plates . if charge on capacitor plate is 1uC d force on each capacitor is??

ans 0.05N

Asked By: SARIKA SHARMA
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Joshi sir comment

F = σq/2ε0 = Eq/2 = 105*10-6/2 = 0.05

Physics >> Electricity >> Capacitors AIEEE

A charge of +2.0 x 10^-8 C is placed on the positive plate and a charge of -1.0 x 10^-8 C on the negative plate of a parallel plate capacitor of capacitance 1.2 x 10^-3 uF. Calculate the potential difference developed between the plates. Please add explanation!

Asked By: VISHWAJEET MISHRA
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Joshi sir comment

 

due to induction the charges on the four faces will be

 

so V = q/C = 1.5 * 10-8/1.2 * 10-9

solve now

Physics >> Electricity >> Capacitors IIT JEE
One end of a 10cm long silk thread is fixed to a large vertical surface of a charged nonconducting plate having a mass 10g and a charge of 4*10^-6 c . In equlibrium the thread makes an angle of 60 deg. With he vertical.find the surface charge density on plate.
Asked By: GAURAV MAHATE
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Joshi sir comment

according to the diagram 

tanθ = qE/mg = q(σ/2ε0)/mg

solve this eq. for σ.

Remember that length of the thread is not applicable in the question.

Physics >> Electricity >> Current Electricity Others

 what is a short circuit?

 

Asked By: SWARNENDU MANNA
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Joshi sir comment

to connect - and + of the cell together

Physics >> Electricity >> Electric Field and Potential Medical Exam

IN THE SOLUTION GIVEN BY AMIT TO MY PREVIOUS QUERY , THE FORMULA USED IS E=kq/r ,SIR I WANT TO KNOW IS IT IS CORRECT , DON'T YOU THINK IT SHOULD BE E=kq/r2 ??

Asked By: SARIKA SHARMA
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Joshi sir comment

yes you are right

Physics >> Electricity >> Capacitors IIT JEE
there is slight mistake in last line of previous question.it was find the work done on the system in the process of inserting the slab.
Asked By: GAURAV MAHATE
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Joshi sir comment

 

initial energy of capacitor = 1/2 CV2

final energy of capacitor = 1/2 KC (V/K)2

difference ?

Physics >> Electricity >> Capacitors IIT JEE
a parallel plate capacitor of plate A and plate seperation d is charged to a potential dif. V and then the battery is disconnected .a slab of dielectric constant K is then inserted between the plates of capacitor so as tofill the space bet. The plates .find the work done in this process.
Asked By: GAURAV MAHATE
is this question helpfull: 3 0 read solutions ( 1 ) | submit your answer
Joshi sir comment

initial energy of capacitor = 1/2 CV2

final energy of capacitor = 1/2 KC (V/K)2

difference ?

Physics >> Electricity >> Electric Field and Potential IIT JEE

A point charge q is placed off centre at point c inside a thick spherical shelll of inner radius a and outer radius b. Shell is neutral and conducting. OA =ra , OB = rb & OC = rc. Then the potential at centre of shell will be ( also show the distribution of charges )

Asked By: AMIT DAS
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Joshi sir comment

Distribution:         at C q, at inner surface -q, at outer surface +q

so potential at centre = kq/rc -kq/a + kq/b

 

Physics >> Electricity >> Electric Field and Potential IIT JEE

A particle P of charge q and mass m is placed at a point in gravity free space and its free to move. another particle Q , of same charge and mass , is projected from a distance r from P with an initial speed v0  towards p . Initially the distance between P and Q decreases and then increases. Then what will be the speeds of particles P and Q when their separation is minimum?

Asked By: AMIT DAS
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Joshi sir comment

by momentum conservation mv0 = 2mv1

so v1 = v0/2 

Physics >> Electricity >> Electric Field and Potential IIT JEE
A charge q kept at the center of a semicircular thread having uniform charge per unit length lameda R is the radius of semivircular thread. Find the force req. ti keep it stationary ???
Asked By: SHUBHAM CHAUDHARY
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Joshi sir comment

first calculate the magnitude of electric field at centre of ring due to charge on the surface of ring and direction of that electric field also

this can be solved by method of integration 

then F = qE

if uncleared reply, we will give complete answer

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