Physics Test 287

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Physics Test 287

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Weekly Quiz Competition

Question 1
4 / -1

An electric dipole placed in a non - uniform electric field experiences

A
Only force but not torque

B
Only torque but not force

C
No torque and no net force

D
Both torque and net force

Solution

When an electric dipole is placed in a non-uniform electric field, the two charges of the dipole ( +q and −q ) experience forces of different magnitudes and/or in different directions because the electric field E is different at the location of each charge.

Net Force: The net force on the dipole is the vector sum of the forces on the individual charges, net net F_net = F₊+ F₋. Since the forces are not equal and opposite in a non-uniform field, the net force is nonzero.

Torque: The forces on the charges also create a turning effect (torque) about the center of the dipole, which tends to align the dipole with the direction of the electric field.

Therefore, an electric dipole in a non-uniform electric field experiences both a net force and a torque.
Question 2
4 / -1

A

B

C

D

Solution
Question 3
4 / -1

Mass of Earth = 6 × 10²⁴ kg
Angular velocity = 2 × 10⁻⁷rad s⁻¹
Radius of orbit = 1.5 × 10¹¹ m

The force exerted by the sun on the earth

A
Zero

B
18 × 10²⁵ N

C
27 × 10³⁹ N

D
36 × 10²¹ N

Solution
Question 4
4 / -1

The mean kinetic energy of one mole of gas per degree of freedom (on the basis of kinetic theory of gases) is

A

B

C

D

Solution
Question 5
4 / -1

Obtain approximately the ratio of the nuclear radii of isotope ²¹⁶X and the isotope ¹²⁵Y (Upto 1 decimal place)

A
1.2

B
1.4

C
0.8

D
1.7

Solution
Question 6
4 / -1

A real gas behaves like an ideal gas if its

A
pressure and temperature are both high

B
pressure and temperature are both low

C
pressure is high and temperature is low

D
pressure is low and temperature is high
Solution
A real gas behaves most like an ideal gas under conditions where intermolecular forces and the volume of the gas particles are minimized.
- Low pressure increases the space between particles, making their individual volume negligible compared to the container volume.
- High temperature increases the kinetic energy of the particles, which helps overcome the intermolecular forces of attraction.
Question 7
4 / -1

A metallic solid sphere is placed in a uniform electric field. The lines of force follow the path(s) shown in figure as

A
1

B
2

C
3

D
4

Solution

Step 1: The electric field inside a metallic solid sphere (a conductor) is zero. Therefore, electric field lines cannot pass through the sphere. Therefore (2) and (3) are not possible.

Step 2: Additionally, electric field lines must be perpendicular to the surface of a conductor. So, first one is not possible.

Answer: Path 4 is the only option that satisfies these conditions, as the line bends around the sphere and is normal to the surface at the points of entry and exit.
Question 8
4 / -1

Consider the charge configuration and a spherical Gaussian surface as shown in the figure. When calculating the flux of the electric field over the spherical surface, the electric field will be due to

A
q₂

B
all the charges

C
only the positive charges

D
+q₁ and −q₁

Solution

1. What the question is asking
The question asks which charges contribute to the electric field whose flux we are evaluating over the given spherical Gaussian surface. It is not asking which charges are enclosed by the surface, nor which charges determine the net flux.
Question 9
4 / -1

The excess pressure inside a soap bubble is twice the excess pressure inside a second soap bubble. The volume of the first bubble is n times the volume of the second where n is

A
4

B
2

C
1

D
0.125

Solution
Question 10
4 / -1

A silver wire has a resistance of 2.0Ω at 0^∘C, and a resistance of 2.4Ω at 100^∘C. Determine the temperature coefficient of resistivity of silver.

A
0.001(^∘C)⁻¹

B
0.002(^∘C)⁻¹

C
0.004(^∘C)⁻¹

D
0.008(^∘C)⁻¹

Solution

The resistance of a material changes with temperature according to the formula: