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  • (a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.

     

    ( b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].

     

    (c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.

     

                                                                    

(a) A conductor A with a cavity as shown | Class 12 Physics Chapter Electric Charges and Field, Electric Charges and Field NCERT Solutions

Q28.

(a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.

 

( b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].

 

(c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.

 

                                                                

(a) Let us consider a Gaussian surface that is lying wholly within a conductor and enclosing the cavity. The electric field intensity E inside the charged conductor is zero.

Let q is the charge inside the conductor and \(\epsilon_{0}\) is the permittivity of free space.

 

According to Gauss’s law,

 

Flux, \(\phi = \overrightarrow{E}.\overrightarrow{ds} = \frac{q}{\epsilon_{0}}\)

 

Here, E = 0

 

\(\frac{q}{\epsilon_{0}} = 0\)

 

\(\because\epsilon_{0} \neq 0\)

 

\(\therefore q=0\)

 

Therefore, charge inside the conductor is zero. The entire charge Q appears on the outer surface of the conductor.

 

(b) The outer surface of conductor A has a charge of amount Q. Another conductor B having charge +q is kept inside conductor A and it is insulated from A. Hence, a charge of amount −q will be induced in the inner surface of conductor A and +q is induced on the outer surface of conductor A. Therefore, total charge on the outer surface of conductor A is Q + q.

 

(c) A sensitive instrument can be shielded from the strong electrostatic field in its environment by enclosing it fully inside a metallic surface. A closed metallic body acts as an electrostatic shield.

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Important Questions & Answers

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This question is important because it tests key concepts from the NCERT syllabus and is frequently asked in CBSE exams.

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Students often lose marks by skipping steps, writing incomplete explanations, or misunderstanding keywords used in the question.

What is the correct answer to: (a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.   ( b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].   (c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.                                                                   ?

(a) Let us consider a Gaussian surface that is lying wholly within a conductor and enclosing the cavity. The electric field intensity E inside the charged conductor is zero.

Let q is the charge inside the conductor an...

How do you solve (a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.   ( b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].   (c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.                                                                    step by step?

Step-by-step explanation:
• (a) Let us consider a Gaussian surface that is lying wholly within a conductor and enclosing the cavity
• The electric field intensity E inside the charged conductor is zero
•
•
• Let q is the charge inside the conductor and \(\epsilon_{0}\) is the permittivity of free space

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Student Discussion

Arushi
Class · · , · Jul 28, 2019
Thank you very much
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nishma
Class · · , · Jun 28, 2019
good explanation
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Aashik
Class · · , · May 16, 2019
So help full
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Sachin
Class · · , · Feb 20, 2019
Nyc sir
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