Physics Test 241

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Physics Test 241

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Question 1
4 / -1

A bullet is fired from a gun, the force on the bullet is given by F = 600 − 2 × 10⁵t where F is in newton and t in second. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet?

A
9 N − s

B
0

C
0.9 N − s

D
1.8 N − s

Solution
Question 2
4 / -1

Two parallel plate air capacitors of same capacity C are connected in series to a battery of emf E. Then one of the capacitors is completely filled with dielectric material of constant K. The change in the effective capacity of the series combination is

A

B

C

D

Solution
Question 3
4 / -1

An ionization chamber with parallel conducting plates as anode and cathode, has 5 × 10⁷ electrons and the same number of singly charged positive ions per cm³. The electrons are moving towards the anode with velocity 0.4 m/s. The current density from anode to cathode is 4μA/m². The velocity of positive ions moving towards cathode is

A
0.4 ms⁻¹

B
zero

C
1.6 ms⁻¹

D
0.1 ms⁻¹

Solution
Question 4
4 / -1

Column - I gives certain physical terms associated with flow of current through a metallic conductor.

Column - II gives some mathematical relations involving electrical quantities. Match Column - I and Column - II with appropriate relations.

A
(A) - (R), (B) - (Q), (C) - (S), (D) - (P)

B
(A) - (R), (B) - (S), (C) - (P), (D) - (Q)

C
(A) - (R), (B) - (S), (C) - (Q), (D) - (P)

D
(A) - (R), (B) - (P), (C) - (S), (D) - (Q)

Solution

Let us define the given options one by one.

A) Drift Velocity - Drift velocity is defined as the average velocity of the particles like electrons which are moving in a random direction when we apply an electric field to them. It is written as;

Where v_dis the drift velocity.

E is the electric field.

τ is the relaxation time and m is the mass.

Therefore, (A) - (R)

B) Electrical resistivity - Electric resistivity is defined as the reciprocal of conductivity and according to ohm's law the conductivity of the material with current density is written as;

where J is the current density, E is the electric field and ρ is resistivity.

Therefore, (B) - (S)

C) Relaxation period - The relation period is also known as relaxation time. It is defined as the short time interval that is taken to achieve the final position from the initial position when an electric field is applied to it. Therefore, it is written as;

where, τ is relaxation time, m is the mass, e is the electron and ρ is the resistivity of the material.

Therefore, column ( C ) - ( P )

D) Current Density: Current density is defined as the amount of charge that is flowed per unit of time through a unit area cross-section. It is written as;

Where J is the current density, e is the electron and v is the velocity.

Therefore, columns ( D ) - ( Q )

Hence, we have (A) - (R), (B) - (S), (C) - (P), (D) - (Q) .

Therefore, option 2) is the correct answer.
Question 5
4 / -1

The wave motion of electron in a Bohr's orbit of hydrogen is as shown in diagram. The potential energy of electron in the given orbit of hydrogen atom is:

A
− 3.4 eV

B
+ 3.4 eV

C
− 3.02 eV

D
− 1.51 eV

Solution
Question 6
4 / -1

A proton accelerated from rest through a potential difference of V volts has a wavelength λ associated with it. An alpha particle in order to have the same wavelength must be accelerated from rest through a potential difference of:

A
V volt

B
4V Volt

C
2V Volt

D

Solution
Question 7
4 / -1

The wavelength of radiation is λ₀ When an electron jumps from third to second orbit of hydrogen atom. For the electron to jump from the fourth to the second orbit of the hydrogen atom, the wavelength of radiation emitted will be

A

B

C

D

Solution
Question 8
4 / -1

A very long conducting wire is bent in a semicircular shape from A to B as shown in figure. The magnetic field at point P for steady current configuration is given by:

A

B

C

D

Solution

Calculation:

In a semicircular shape, we can use the Biot-Savart law, which gives the magnetic field produced by a current element.

For a current-carrying wire, the Biot-Savart law is expressed as:
Question 9
4 / -1

If the density of air is ρ_a and that of the liquid ρ_l, then for a given piston speed the rate (volume per unit time) at which the liquid is sprayed will be proportional to

A

B

C

D

Solution
Question 10
4 / -1

If W₁,W₂ and W₃ represent the work done in moving a particle from A to B along three different paths, 1,2 and 3, respectively, (as shown in the figure) in the gravitational field of a point mass m, find the correct relation between W₁, W₂ and W₃.

A

B

C

D

Solution

Calculation:

Work done under a conservative force such as gravitation is only dependent on displacement between final & initial points.