# Q&A - Ask Doubts and Get Answers

Sort by :
Clear All
Q

Which of the following acts as a circuit protection device ?

• Option 1)

conductor

• Option 2)

inductor

• Option 3)

switch

• Option 4)

fuse

fuse Option 1)conductor Option 2)inductor Option 3)switch Option 4)fuse

In which of the following devices , the eddy current  effect is not used ?

• Option 1)

induction furnace

• Option 2)

magnetic braking in train

• Option 3)

electromagnet

• Option 4)

electric heater

electric heater Option 1)induction furnace Option 2)magnetic braking in train Option 3)electromagnet Option 4)electric heater

Pick the wrong answer in the context with rainbow

• Option 1)

When the light rays undergo two internal  reflection in a water drop , a secondary rainbow is formed

• Option 2)

The order of colors is reversed in the secondary rainbow

• Option 3)

An observer can see a rainbow when his front is towards the sun

• Option 4)

Rainbow is a combined effect of dispersion , refreaction and reflection of sunlight

Rainbow can seen when back is towards the Sun.Option 1)When the light rays undergo two internal  reflection in a water drop , a secondary rainbow is formed Option 2)The order of colors is reversed in the secondary rainbow Option 3)An observer can see a rainbow when his front is towards the sun Option 4)Rainbow is a combined effect of dispersion , refreaction and reflection of sunlight

A particle moving with velocity $\vec V$ is acted by three forces shown by the vector triangle PQR . The velocity of the particle will :

• Option 1)

increase

• Option 2)

derease

• Option 3)

remain constant

• Option 4)

change acording to the smallest force QR

Option 1) increase  Option 2) derease  Option 3) remain constant  Option 4) change acording to the smallest force QR

Two parallel infinite line charges with linear charges densities $+ \lambda C/ m \: \: and \: \: - \lambda C/ m$ are placed at a distance  of 2R in free space . what is the electric field mid way between the two line charges ?

• Option 1)

zero

• Option 2)

$\frac{2 \lambda }{\pi \epsilon _0 R} N/C$

• Option 3)

$\frac{ \lambda }{\pi \epsilon _0 R} N/C$

• Option 4)

$\frac{\lambda }{2\pi \epsilon _0 R} N/C$

Option 1) zero Option 2) Option 3) Option 4)

Two similar thin equiconvex lenses , of focal length f each , are kept  coaxially in contact  with each other such that the focal length of the combination is $F_1$ . When the space between the two lenses is filled  with glycerin  then the equivalent  focal length is $F_2$ . The ratio $F_1 : F_2$

• Option 1)

2 : 1

• Option 2)

1 : 2

• Option 3)

2 : 3

• Option 4)

3 : 4

Option 1)2 : 1 Option 2)1 : 2 Option 3)2 : 3 Option 4)3 : 4

The total energy of an electron in an atom in an orbit is -3.4 eV . Its kinetic and potential energies are respectively

• Option 1)

-3.4 e V, -3.4 eV

• Option 2)

-3.4 e V , - 6.8 e V

• Option 3)

3.4 e V , - 6.8 e V

• Option 4)

3.4 e V , 3.4 e V

Option 1) -3.4 e V, -3.4 eV  Option 2) -3.4 e V , - 6.8 e V  Option 3) 3.4 e V , - 6.8 e V  Option 4) 3.4 e V , 3.4 e V

A soap bubble , having radius of 1 mm is blown from, a detergent solution having a surface tension , of $2.5 \times 10 ^{-2 } N/m$. The pressure inside the bubble equals at a point $Z_0$ below  the free surface of water in a container of water = $10 ^ 3 Kg / m ^ 3$ , the value of $Z_0$ is

• Option 1)

100 cm

• Option 2)

10 cm

• Option 3)

1 cm

• Option 4)

0.5 cm

Option 1)100 cm Option 2)10 cm Option 3)1 cm Option 4)0.5 cm

The unit of thermal conductivity is :

• Option 1)

$JmK^{-1}$

• Option 2)

$Jm^{-1}K^{-1}$

• Option 3)

$WmK^{-1}$

• Option 4)

$Wm^{-1}K^{-1}$

Option 1)Option 2)Option 3)Option 4)

A parallel palte capacitor of capacitance $20 \mu F$ is being charged by a voltage source whose potential is changing at the rate of 3 V/s . The conduction  current through the connecting wires , and the dispalcement  current through the plates of the capacitor , would be  resectively :

• Option 1)

zero, $60 \mu A$

• Option 2)

$60 \mu A , 60 \mu A$

• Option 3)

$60 \mu A , zero$

• Option 4)

zero , zero

Option 1)zero, Option 2)Option 3)Option 4)zero , zero

When a object is shot from the bottom of a long smooth inclined plane kept at an angle $60 \degree$ with horizontal , it can travel a distance $x_1$ along the plane . But when the inclination is decreased  to $30 \degree$ and the same object is shot with the same velocity , it can travel$x_2 \: \: distance .\: \: Then\: \: x_1 : x_ 2 \: \: will\: \: be :$

• Option 1)

$1 : \sqrt 2$

• Option 2)

$\sqrt 2 : 1$

• Option 3)

$1 : \sqrt 3$

• Option 4)

$1 : 2 \sqrt 3$

Option 1)Option 2)Option 3)Option 4)

A small hole of area of cross sectyion $2 mm ^ 2$ is  present mear the botom  of a fully  filled open tank  of heiht 2 m . Taking $g = 10 m /s ^2$ , the rate of flow of water through the open hole would be nearly :

• Option 1)

$12.6 \times 10 ^{-6 } m^3 / s$

• Option 2)

$8.9 \times 10 ^{-6 } m^3 / s$

• Option 3)

$2.23 \times 10 ^{-6 } m^3 / s$

• Option 4)

$6.4 \times 10 ^{-6 } m^3 / s$

Option 1) Option 2) Option 3) Option 4)

A disc of radius 2 m and mass 100 Kg rolls on a horizontal floor . Its center of mass has speed of 20 cm/s . How much work is needed to stop it ?

• Option 1)

3 J

• Option 2)

30 Kj

• Option 3)

2 J

• Option 4)

1 J

Option 1)3 J Option 2)30 Kj Option 3)2 J Option 4)1 J

A force F  = 20 + 10 y acts on a particle in y - direction  where F  is in newton and y in meter  Work done by this force to move the particle from y = 0 to y = 1 is :

• Option 1)

30 J

• Option 2)

5 J

• Option 3)

25 J

• Option 4)

20 J

Option 1)30 J Option 2)5 J Option 3)25 J Option 4)20 J

A body weighs 200 N on the surface of the earth  how much will it weigh at half way down to the center of the earth ?

• Option 1)

150 N

• Option 2)

200 N

• Option 3)

250 N

• Option 4)

100 N

Option 1) 150 N  Option 2) 200 N  Option 3) 250 N  Option 4) 100 N

Body A of mass 4m moving with speed u colloides with another body B ofmass 2m , at rest . The collision is head on and elastic in nature . After the colloision the fraction of energy lost by the colliding body A is :

• Option 1)

1/9

• Option 2)

8/9

• Option 3)

4/9

• Option 4)

5/9

Option 1) 1/9  Option 2) 8/9  Option 3) 4/9  Option 4) 5/9

$\alpha$ particle constist of :

• Option 1)

2 protons and 2 nuetrons only

• Option 2)

2 electrons , 2 protons and 2 nuetrons

• Option 3)

3 electrons and 4 protons

• Option 4)

2 protons only

Option 1) 2 protons and 2 nuetrons only  Option 2) 2 electrons , 2 protons and 2 nuetrons  Option 3) 3 electrons and 4 protons  Option 4) 2 protons only

Two point charges A and B , having charges Q and - Q respectively , are placed at a certain distance apart ad force acting between them is F . If 25 % charge of A is transferres to B , then force between he charges  becomes :

• Option 1)

• Option 2)

9F/16

• Option 3)

16F/9

• Option 4)

4F/3

Option 1) F  Option 2) 9F/16 Option 3) 16F/9 Option 4) 4F/3

In total internal reflection when the angle of incidende is equal to the critical angle for the pair of media in contact  what will be angle of refraction ?

• Option 1)

180

• Option 2)

• Option 3)

equal to angle of incidence

• Option 4)

90

For internal refection  at Option 1)180 Option 2)0 Option 3)equal to angle of incidence Option 4)90

The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth is :

• Option 1)

mgR

• Option 2)

2 mgR

• Option 3)

1/2 mgR

• Option 4)

3/2 mgR

Option 1) mgR  Option 2) 2 mgR  Option 3) 1/2 mgR  Option 4) 3/2 mgR
Exams
Articles
Questions