Explore topic-wise InterviewSolutions in Current Affairs.

1. a. Hydrogen,helium

2. b. 4

3. c. Nuclear fusion, hydrogen

4. b. FALSE

5. a. TRUE

True

Selenium makes more efficient solar cells which converts a great percentage of solar energy into electrical energy.

Animals in the forest find shelter from cold in holes in the snow because snow has trapped air (as in ice there is no air) so, it acts as a heat insulator. Therefore, the snow prevents the transmission of heat from the body of the animal to the outside.

Given: 

Solar Constant = 1.4 kW/m² 

Solution: 

Solar energy received at area of 1 m² = 1.4 kW/m² 

So the energy received at an area of 5m² = 5 × 1.4 

= 7 kW/m²

1. a. 0.5 V

2. b. 25

3. a. TRUE

4. c. Silver

5. a. TRUE

1. a. Solar cells

2. b. Electrical

3. c. Silicon

4. a. TRUE

5. b. Glass

(a) Solar water heater would have been a good choice No moving parts, little maintenance, work satisfactorily without any focusing device. Can be set up in remote and inaccessible hamlets or sparsely inhabited areas 

(b) Possible changes in family's thinking 

(i) Harnessing the natural and greatest source of energy, the sun 

(ii) Savings on electricity bills in the future

Solar cell panel consists of a large number of solar cells joined together in a definite pattern. It is used to convert solar energy into electricity. Advantages of solar cell panel are:- 

1. It provides much more electric power than a single solar cell. 

2. It is used to provide electricity in remote and inaccessible rural areas. 

1. a. Kinetic

2. a. TRUE

3. b. Wind generator

4. c. Wind energy farm

5. d. 15 km/hr

Solar constant is 1.4kW/m² or 1.4 kJ/s/m² . 

Solar energy received by 1 m² area in 1 s = 1.4 kJ 

Solar energy received by 1 m² area in one hour (or 3600 s) = 1.4 x 3600 = 5040 kJ

The amount of solar energy received per second by one metre square area of the near earth space (exposed perpendicularly to the sun rays) at an average distance between the sun and the earth, is known as solar constant. Its value is 1.4 kJ/s/m²

One steradian is defined as the angle made by a spherical plane of area 1 square meter at the centre of a sphere of radius 1m. 

A^o and A.U. both are the units of distances but 1A^o = 10^-10m and 1A.U. = 1.496× 10¹¹m.

Area, A=5m² ; time,t=10 min=600sec; E=4200 kJ. 

Solar constant =E/(Axt) 

=4200/(5×600) 

=1.4 kJ/s/m²

Image is virtual and erect. 

• Size of the image is equal to that of object 

• Image is laterally inverted. 

• The image formed by a plane mirror is always at the same distance as the object is in front of it.

Mirrors, whose reflecting surfaces are spherical, are called spherical mirrors.

Mirrors whose reflecting surface are part of a sphere are called spherical mirrors.

The Correct option is B. Neutron

The correct option is A) Soft iron.

The core of the transformer is made up of soft iron to increase the magnetic field and this helps in saving of energy.

Let F = K m^a v^b r^c

Where K is the dimensionless constant of proportionality and a, b, c are the powers of m, v and r respectively to represent F.

Writing the dimensions of various quantities in equation (ii), we get

[M¹L¹T^-2] = [M]^a [LT^-1]^b [L]^c

= M^a L^b T^-b L^c = M^a L^b + T^-b

Applying the principle of homogeneity of dimensions we get

a = 1, b +c = 1

-b = -2 or, b = 2

From (ii) c = 1 -b = 1 -2 = -1

Putting the values of a,b and c, in (i) we get

F = K m¹ v² r^-1

or, F =K mv²/r

The correct option is (B) Neutron.

Neutron is not accelerated by electric field.

Let MKS unit of force = n × CGS unit of force

n = MKS unit of force/CGS unit of force

= kg ms^-2/gm cms^-2

= kg ms^-2/10^-3 kg 10^-2 ms^-2

= 1/10^-5 = 10⁵

∴ MKS unit of force = 10⁵ CGS unit of force i.e., 1 newton = 10⁵

(d) water current

Correct answer is (c) 40

Correct answer is (d) SI

Displacement by the car is 11 m.

u = 5 m/s.

t = 5s

v = 15 m/s

a = \(\frac{\text{v}\,-\,\text{u}}{t}=\frac{15-5}{5}=\frac{10}{5}\)

= 2 m/s²

s = ut + 1/2 at²

= 5 × 5 + 1/2 × 2 × 5²

= 25 + 25

= 50 m

v = u + at

u = 0

= 0 + 5 m/s² x 60 s

a = 5m/s²

= 0 + 300 m/s

t = 1

mt = 60 sec

= 300 m/s

s = ut + 1/2 at²

= 0 × 60 + 1/2 × 5 × 60

= 9000 m

One marble will be thrown off from the other end and reaches the previous position.

When the change in momentum is a constant, the force acting on a body will be inversely proportional to the time taken. As time increase, the force acting decreases and as time decreases, the force acting increases.

m = 5 kg,

u = 3 m/s,

v = 7 m/s,

t = 2s

a = \(\frac{\text{v}-\text{u}}{t}\)

= \(\frac{7m/s-3m/s}{2s}\)

= 2 m/s²

Force F = ma = 5 kg x 2 m/s²

= 10 kg m/s²

= 10 N

Yes, the vehicle moves Internal forces can not move an object, but only an external unbalanced force can cause motion.

Newton’s First Law Of Motion

Every object continues in its state of rest or of uniform motion along a straight line unless an unbalanced external force acts on it. This is Newton’s First law of motion

The vehicle doesn’t move.

Bus. Because when mass increases momentum increases.

(a) Increases 

(b) 1 Newton (1N)

(d) B implies A but A does not imply B.

Sir Isac Newton ceased to live on earth.

(d) m₁vector v + m₂ vectorv₂ must be parallel to vector v.

Explanation: 

Linear momentum, which is a vector, is conserved of a system if no external force is acted upon. The direction of the velocity of the nucleus v is same as its momentum. The momentum after emission of ɑ-particle m₁v₁ + m₂v₂ will have the same direction as v due to conservation principle.

(d) momentum, but neither kinetic energy nor temperature.

Explanation: 

Since velocities of the colliding bodies change, the K.E. will change. The shapes of the bodies at the time of collision change due to the force, hence temperature will also change. Only the momentum will remain constant.

(d) momentum, but neither kinetic energy nor temperature.

Explanation: 

Since velocities of the colliding bodies change, the K.E. will change. The shapes of the bodies at the time of collision change due to the force, hence temperature will also change. Only the momentum will remain constant.

Since the plank is light its mass is negligible in comparison to the fat person. Combined center of mass of the system containing the fat person and the plank can be considered near the person. Since there is no external force on this system the center of mass of the system will remain at the same place. Due to this the friend on the shore finds the fat person hardly move.

Yes. Since Z-coordinate of each particle will be zero, hence ഽz.dm=0. So Z-coordinate of the center of mass Z=(1/M)ഽz.dm=0. So the center of mass lies in the X-Y plane.

(a) the initial kinetic energy is equal to the final kinetic energy 

Explanation: 

The initial kinetic energy before the collision and the final kinetic energy after the collision will remain the same. We cannot say that (c) is true because during the contact a part of the kintic energy is stored as elastic potential energy in the bodies, and at this time total kinetic energy is less than the initial or final kinetic energy.

No, because the linear momentum will not be conserved. For example, consider the one-dimensional collision of mass m with velocity 2v and mass 2m with velocity v before the collision. Total momentum = m.2v+2m.v = 4mv. Had the velocities been interchanged after the collision, final momentum of the system would be = m.v+2m.2v = 5mv, which is not according to the principle of conservation of the linear momentum. So the velocities, in this case, will not be interchanged.

(b) the linear momentum remains constant
(c) the final kinetic energy is equal to the initial kinetic energy
(d) the final linear momentum is equal to the initial linear momentum.

Explanation: 

In a fully elastic collision only during the contact period a part of the kinetic energy is stored as elastic potential energy in the bodies and their shapes are slightly changed. Since the collision is elastic the bodies release the stored elastic potential energy and regain their shape. Again the total energy is in the form of K.E. Hence the final K.E. is equal to the initial K.E. But we can not say that the K.E. remains constant because during the contact period it is reduced. So (c) is true and (a) false. 

When there is no external force the momentum is conserved. Hence (b) and (d) is true.