Physics Test

Result

Physics Test - 25

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
5 / -1

Calculate the value of peak reverse voltage (P.I.V.) if the full-wave rectifier has an alternating voltage of 300 V.

A
849 V

B
800 V

C
750 V

D
870 V

Solution

Given: E_rms = 300 V

The required equation is → P.I.V. = 2 × E₀ or P.I.V. = 2√2 × E_rms

P.I.V. = 2√2 × 300 V

P.I.V. = 848.52 V ≈ 849 V.
Question 2
5 / -1

What focal length should the reading spectacles have for a person for whom the least distance of distinct vision is 50 cm?

A
+ 25 cm

B
– 25 cm

C
+ 50 cm

D
– 50 cm

Solution

By thin lens formula,

1/f = 1/v - 1/u

1/f = 1/(-50) - 1/(-25)

f = +50 cm.
Question 3
5 / -1

In Young’s double-slit experiment if the distance between two slits is halved and distance between the slits and the screen is doubled, then what will be the effect on fringe width?

A
Doubled

B
Decreases four times

C
Increases four times

D
Halved

Solution

Original fringe width is given as → β = Dλ/d.
Question 4
5 / -1

A lens has a focal length of 10 cm. Where the object should be placed if the image is to be 40 cm in the positive direction from the lens?

A
12 cm

B
40 cm

C
13 cm

D
0.075

Solution

Given: f = + 20 cm; v = + 40 cm

The required equation →
Question 5
5 / -1

An object is to be seen through a simple microscope of power 10 D. Where should the object be placed to reduce maximum angular magnification? The least distance for distinct vision is 25 cm.

A
+ 7.1 cm

B
– 7.1 cm

C
+ 25 cm

D
– 25 cm

Solution

Angular magnification is maximum when the final image is formed at the near point.

u = -7.1 cm.

Therefore, the object should be placed 7.1 cm before the lens to avoid angular magnification.
Question 6
5 / -1

If the separation between the two slits is decreased in Young’s double-slit experiment keeping the screen position fixed, what will happen to the width of the fringe?

A
Decreases

B
Increases

C
Remains the same

D
Independent

Solution

Fringe width is expressed as:

β = Dλ/d.

So, as the separation (d) between the two slits decreases, the fringe width increases. They are inversely proportional to each other.
Question 7
5 / -1

What is the rms value of output current if the peak value of output current is given as 0.092 A?

A
0.65 A

B
6.5 A

C
0.45 A

D
0.065 A

Solution

Given: I₀ = 0.092 A

The required equation is → I_rms = I_o/√2

I_rms = 0.092/1.414

I_rms = 0.065 A
Question 8
5 / -1

Find the magnification of the lens if the focal length of the lens is 10 cm and the size of the image is -30 cm.

A
2

B
3

C
4

D
5

Solution

Given: f = +10 cm; v = -30 cm

Required equations →

1/f = 1/v - 1/u

m = (size of the image/size of the object) = v/u

u = (-15)/2 = -7.5cm

m =v/u = -(30/(-7.5)) = -300/-75 = +4

Therefore, the object should be placed at a distance of 7.5 cm from the lens to get the image at a distance of 30 cm from the lens. It is four times enlarged and is erect.
Question 9
5 / -1

Radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains?

A
1080

B
2430

C
3240

D
4860

Solution
Question 10
5 / -1

Why is there a sudden increase in current in Zener diode?

A
Due to the rupture of ionic bonds

B
Due to rupture of covalent bonds

C
Due to viscosity

D
Due to potential difference

Solution

The sudden increase in current in a Zener diode is due to the rupture of the many covalent bonds present. Therefore, the Zener diode should be connected in reverse bias.