Mix Test

Result

Mix Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

Six resistors, each of resistance R, are connected as shown in the figure. What is the effective resistance between points A and B?

A

B
R

C
3R

D
6R

Solution

Resistances R, (R + R) = 2R, (R + R) = 2R and R are in parallel. Hence, the effective resistance is given by

, which gives
Question 2
1 / -0

A ball, which is at rest, is dropped from a height of 'h' metres. As it bounces off the floor, its speed is 80% of what it was just before touching the ground. The ball will rise to a height of

A
0.94 h

B
0.80 h

C
0.75 h

D
0.64 h

Solution

Let the velocity of ball after re-bounce be u. Let the ball reach the height h.
Question 3
1 / -0

If the radius of Earth shrinks by 1.5% (mass remaining the same), then the value of acceleration due to gravity would change by

A
3%

B
6%

C
9%

D
12%

Solution

We know that g = , where G and M are constants.

Now,

Therefore, if R decreases, g increases.

Percentage change in the acceleration due to gravity,

%
Question 4
1 / -0

Wires AB and BC, each of length L/2, are made of the same material. The radius of wire AB is 2r and that of wire BC is r. The current I flows through the composite wire. Which of the following statements is true?

A
Potential difference across BC is twice across AB.

B
Electric fields in AB and BC are equal.

C
Current densities in AB and BC are equal.

D
Power dissipated in BC is four times the power dissipated in AB.

Solution
Question 5
1 / -0

In a semiconductor, it is found that th of the total current is carried by electrons and the remaining by holes. If at this temperature, the drift speed of electrons is 2.5 times that of the holes, then the ratio of the number density of electrons to that of holes is

A

B

C

D

Solution
Question 6
1 / -0

Two wires A and B of the same material having radii in the ratio 1 : 2 carry currents in the ratio 4 : 1. The ratio of the drift speeds of electrons in A and B is

A
16 : 1

B
^{4 : 1}

C
^{8 : 4}

D
2 : 1

Solution

I = neAv_dLet the drift velocity in A is v_d1 and in B it is v_d2current in A is I₁ and in B it is I₂
Question 7
1 / -0

What is the dimensional formula of Planck's constant?

A
M¹L²T^-1

B
M¹L²T^-2

C
M^-2L^-1T²

D
None of these

Solution

h = =
Question 8
1 / -0

A convex lens of focal length 50 cm and a concave lens of focal length 100 cm are separated by a distance of 10 cm. What is the power of combination?

A
+1.5 D

B
+1.2 D

C
-0.6 D

D
Zero

Solution

For the combination of lenses, effective focal length,
Question 9
1 / -0

The primary of a transformer has 400 turns, while the secondary has 2000 turns. If the power output from the secondary at 1000 V is 12 kW, then the resistance of the primary is 0.2, the resistance of the secondary is 2and the efficiency of the transformer is 80%. The power loss in the primary is

A
1.125 kW

B
2.25 kW

C
3.375 kW

D
4.5 kW

Solution
Question 10
1 / -0

In a double slit experiment, instead of taking slits of equal widths, one slit is made twice as wide as the other. What will happen in the interference pattern?

A
The intensities of both maxima and minima increase.

B
The intensity of the maxima increases and that of minima is zero.

C
The intensity of the maxima decreases and that of the minima increases.

D
The intensity of the maxima decreases and that of minima is zero.

Solution
Question 11
1 / -0

A 0.5 kg mass moving with a speed of 1.5 m/s on a horizontal smooth surface collides with a nearly weightless spring of force constant k = 50 N/m. The maximum compression of the spring would be

A
0.15 m

B
0.12 m

C
1.5 m

D
0.5 m

Solution

By the law of conservation of energy, kinetic energy of mass = energy stored in spring.
Question 12
1 / -0

A Carnot engine operates with a source at 500 K and a sink at 375 K. The engine consumes 600 kcal of heat per cycle. The heat rejected to the sink per cycle is

A
250 kcal

B
350 kcal

C
450 kcal

D
550 kcal

Solution
Question 13
1 / -0

The threshold wavelength for a metal whose work function is W₀ is . What is the threshold wavelength for a metal whose work function is W₀/2?

A

B

C
2

D

Solution
Question 14
1 / -0

A solid cylinder of mass M and radius R rolls down an inclined plane without slipping. In doing so, it comes down a height h. The speed of its centre of mass when it reaches the bottom is

A

B

C

D

Solution

KE = = = KE = Loss in PE

v =
Question 15
1 / -0

The force of attraction between the plates of an air-filled parallel plate capacitor having charge Q and area of each plate A is given by

A

B

C

D

Solution