physics electrostatics mcq[1]

7/26/2019 Physics Electrostatics MCQ[1]

1/8

13 - ELECTROSTATICS Page 1

(

Answers

at the

end

of

all questions

)

t ) Two point

charges

+ 8q

and

- 2q

are located

at x =0

and l t

=L respectively.

The

location

of a point on the

x

axis

at

which the

net electric field

due to these two point

charges is zero is

a )

Ll4

b )

2L

c )

4L d )

8L

2 )

Two thin wire

rings each having a radius R are

placed

at a distance

axes coinciding. The charges on the two rings are + q and - q. The

between the centres of the two rings is

a -q-

1

~ ~ : e o R

1

I b I

q q

1

I

c

I

4 ~ r e o R

3

J

A parallel plate capacitor is made by stacking . . p c e d

alternatively.

If

the capacitance between any two ~ e s is 'C',

capacitance

Is

a ) n + 1 ) C b } n - 1 } C c ) ~ C

4 ) A charged ball

B

hangs from a silk

t h r ~ h.

makes an angle

with a large conducting

sheet

P as sho in figure. The surface

charge

density o of the

sheet

is pr to

a )

cot

( b 1 cos e

( c) tan

( d I

d

their

d ) zero

I AIEEE 2005 I

plates connected

then the

resultant

I

AIEEE 2005

I

+

v

I AIEEE 2005]

6 ) B

and

C having equal radii

and

carrying

equal

charges in them

force F when kept apart

at

some

distance. A

third spherical

r

having

same radius as

that of

B

but

uncharged, is

brought

in

contact

with

B

brought in contact

with

C

and finally

removed

away from both.

The

new

force

of

. . . . . . : ~ a . r e p u lsion between B

and

C

is

a I

F

I 4 ( b I

3 F

I ( c I

F

I

8

d I

3 F

I

8

I AIEEE 2004 ]

A charged particle q is shot

towards another

charged particle Q which is fixed, with a

speed v. It

approaches

Q

upto

a

closest

distance r and then returns.

If

q was given a

speed

2v, the closest distance of

approach

would be

.

q ===-+ Q

.-r-.

a )

r

b )

2r

c )

r l 2

d )

rl

I

AIEEE 2004 ]


2/8

8

I

13 - ELECTROSTATICS

Answers

at the

end

of

all questions

1

Four charges equal

to

-Q are placed at the

four

corners of the

Is at its centre. If the system is In equilibrium, the value of q

is

a

} -

Q I t + 2 /2} b

I

1 + 2 /2

I I

c

I -

1 + 2 /2

I

4 4 2

Page 2

square and a charge q

I d I

9 }

Three

charges

-q1, +q2

and

-q3 are placed as

shown in the figure.

The x-component

of

the

force on -q1 is proportional

to

y

a 1 q

2

- q

3

sin 9 b } q

2

- q

3

cos 9

b2 a2 b2 a2

c 1 q

2

+

q

3

sine d 1 q

2

+

q

3

sin 9

b2 a2 b2 a2

[ AIEEE 2003 ]

10

I

A

d )

12 1

The

work done

)(

q

charge

Q

is

placed

P at a distance R /2

from

2Q

q

4ll t:,R

4,.;t:,R

I AIEEE 2003 I

respectively,

the

I AIEEE 2003 I

condenser of

capacity

I

AIEEE 2003 ]

is

introduced between the plates of a

d I remains unchanged

I AIEEE 2003 I

of

a cube, the magnitude

of

flux

through

one of Its

d ) 6q/e . [ AIEEE 2003

I

15

1

A

charged

capacitor is discharged by using a

wire

and equation

of

decreasing charge

in

wire

is

q =

0.1

elt

coulomb. The

current

in

the wire

at

t = 2 sec

will

be

a 1 0.1/e

6

b 1 0.3/e

6

c 1 0.5/e

6

d 1 0.7/e

8

[AIEEE 2002)

16

1 I f

n capacitors each of capacitance C are connected in series with a battery of V volt,

then the energy stored in all the

capacitors

will be

a } nCV

2

b } nCV

2

/4

c

I

nCV

2

/2

d

I

CV

2

/2n

[ AIEEE

2002]


3/8

13 - ELECTROSTATICS

Page 3

(

Answers

at the

end

of

all questions

)

t7 ) A conducting

sphere

of radius 10 em is charged with 10 ).IC. Another uncharged

sphere

of

radius

20 em is

allowed

to touch it

for

some time. I f both the

spheres

are

separated,

18

I

then surface density

of

the charges on

the

spheres will

be in

the

ratio of

a ) 1 : 4 b ) 4 : 1 e ) 1 : 2 d ) 2:1

Sixty four equal

charged

each drop is 10 volt, then

a ) 10V b ) 40V

drops are combined

to

form a

big

the potential of the

big

drop wIll be

c ) 160V d )

640V

drop.

I

ial

on

2002

19

) Three large charged sheets are having surface

charge

density

as

shown in the figure.

The

sheets

are

placed

parallel to XV plane. Then

electric field

at point P

will

be

.A

k

A

a )

4

a

k b )

4

a

k

+

-2

o

o o - - - , , - - - , - - + - - - -

z = 3a

p

z = a

c )

2 J k

o

( d

I

A

2 J k

o

z

= 0

20 ) Consider the

charge

configuration

Gaussian surface

as

shown in the figure. When flux of the

electric

field over

the

spherical surface,

due to

a

) q2

b

I

( c ) all

the

charges ( d

. (iT 2004 I

21 )

Six charges, three and three

negative, of

equal

P ~ I Q

such that the e e at 0 is double

the

electric field when

only

one

positiv e of the same

magnitude

is placed at R. U

Which

of e folio

ng arrangement

of

charges

Is possible

for

o R

P, Q, R, T d

respectively

7

a ) b +,-,+,-,+,- T ~ . J s

( c ( d } -, +,

+,

- , +, -

)l iT

2004

J

shell has

a point

charge

q kept

inside

its cavity.

Which one

of the

owing

diagrams correctly

represents the

electric

lines

of

forces ?

a

I

l iT

2003

J


4/8

13 - ELECTROSTATICS

Page 4

(

Answers at

the

end

of

all questions

)

23 ) Two equal

point

charges are fixed at x -a and x

+

a

on the

X-axis.

Another point

charge Q is placed at

the

origin. The change in

the

electrical potential energy of

Q

when

i t

is displaced by

a

small distance

x

along the

X-axis,

is approximately

proportional

to

I

a

I

x

I

b

I

x

2

I

c

I

x

3

I

d

I

1 I x

24 ) Two

identical

C. One

of

th

25

26 I

a)

i

I

J .

I '

: I I

/ /

: /

( q

I liT

2002

J

of

an

equilateral

c )

(d)

I

liT 2001 J

capacitor

A has a charge q

on i t

the

capacitor

B a

long time after

the

I d I

2q

[ l iT

2001 }

q

+

+ .1 - - - - - - - - - -1

+

A

s

J-

B

electric field pointing in positive X dlrection exists in

a region.

Let

A

be the

be the point on the

X-axis at x

=

1 em and C

be the point on the

Y-axis

at

em. Then the potentials at

A, B

and

C

satisfy

VA< VB

b )

VA> VB

c )

VA Vc [ l iT 2001}

Three charges Q + q and + q are placed at

the

vertices of

Q

a

right angled isosceles triangle as shown in

the

figure.

The

net electrostatic energy of

the

configuration is

zero

i f Q is

equal to

( a ) - q

1

+ J2

b ) -

2q

2

+ J2

I

c

I - 2q

d ) +

q

I

liT

2ooo

I


5/8

29

I

30

I

31 I

13 - ELECTROSTATICS Page 5

( Answers at the

end

of all

questions

)

A

parallel plate

capacitor of area A plate

separation

d

and capacitance

C is fitted

with three

different

dielectric constants k1, k2

and

k3 as shown in the

figure.

If a single

dielectric material is to

be used

to have

the

same capacitance

C

In

this

capacitor, then

its

dielectric constant k is given by

a

I

I b I

I

c

I

1 1 1

1

=- -

k

1

k

'

k

'

k1 k2

1

k1 + k2

k t k2

k t

k2

+

2 k 3

k t k3

+

k t k2

d ) k '

density at

A

=

charge

density at

A

:enltial at A = potential at B

A

nd

02

(

Qo b I V > Vo I c I E >

Eo

d

: uo

Two equal

negative

charges

-

q

are

fixed at

t h ~ n

, a

1

and

YaKiS.

A

positive

charge

Q Is released at s she int 2a,

0 I

charge Q

will

a 1 execute simple harmonic motion

bft

in

b 1 move to the origin

and

remain

at t

c 1 move to

in

in

ty

d 1 execute oscillatory but not

si

e

nic

motion

{liT

t985J

0,

-a

1

on the

on the Xaxls. The

[liT 1984 J

1 2 3 4 5 11 12 13 14 15 16 17 18 19 20

b d c c c b

a

d c b d d c d c

21 22 23 24 30 31 32 33 34 35 36 37 38 39

40

d c b c d d c.d b c d a.c a c c d a.c d

41

42

a

b d

physics electrostatics mcq[1]

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