Physics Test 274

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Physics Test 274

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Weekly Quiz Competition

Question 1
4 / -1

Three point charges of 1 C, 2 C and 3 C are placed at the corners of an equilateral triangle of side 1 m. The work done (in joules) in bringing these charges to the vertices of a smaller similar triangle of side 0.5 m is

A
9 x 10⁹

B
9.9 x 10¹⁰

C
99 x 10¹⁰

D
5.4 x 10¹⁰

Solution
Question 2
4 / -1

Three capacitors, each of capacity 4 µF, are to be connected in such a way that the effective capacitance is 6 µF. This can be done by

A
Connecting two in series and one in parallel

B
Connecting two in parallel and one in series

C
Connecting all of them in series

D
Connecting all of them in parallel

Solution

To get equivalent capacitance 6 μF, out of the three, 4 μF capacitances, two are connected in series and the third one is connected in parallel.
Question 3
4 / -1

A 3 μF capacitor is charged to a potential of 300 V and a 2 μF capacitor is charged to a potential of 200 V. The capacitors are then connected in parallel with plates of opposite polarity joined together. What amount of charge will flow when the plates are so connected

A
600 μC

B
700 μC

C
250 μC

D
1300 μC

Solution

Before connections,

C₁ = 3µF, V₁ = 300V

Charge on C₁,

Q₁ = 900μC

C₂ = 2µF, V₁ = 200V

Charge on C₂,

Q₂ = 400μC

When the positive terminal of C₁ is connected with the negative terminal of C₂, common potential of the system is:

Substituting the values, we get

V = 100V

New charge on positive plate of C₁,

Q'₁= 3 x 100 = 300µC

So, charge Q1 - Q'₁ = 600 µC has flown from the positive plate of the C₁ to the negative plate of C₂.
Question 4
4 / -1

An insulator plate is passed through the plates of a capacitor as shown. The current

A
First flows from A to B and then, from B to A

B
First flows from B to A and then, from A to B

C
Always flows from B to A

D
Always flows from A to B

Solution

As insulator plate is passed between the plates of the capacitor, its capacity increases first and then decreases as the plate slips out. As a result, positive charge on plate A increase first and then decreases, hence, current in outer circuit flows from B to A and then from A to B.
Question 5
4 / -1

Directions For Questions

Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses.

...view full instructions

Assertion: The electric flux of the electric field ∮ E.dA is zero. The electric field is zero everywhere on the surface.

Reason: The charge inside the surface is zero.

A
If both the Assertion and Reason are incorrect.

B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.

C
If the Assertion is correct but Reason is incorrect.

D
Assertion is false, Reason is true

Solution

By Gauss’s law:

∮ E ⋅ dA = Q_enc / ε₀

If ∮ E ⋅ dA = 0, then Q_enc = 0, so the reason is true. However, the assertion is false: zero flux does not imply E = 0 everywhere on the surface (e.g., a dipole with no net charge produces non-zero field).

Thus, both are not correct, and the correct answer is D: Assertion is false, Reason is true.
Question 6
4 / -1

Directions For Questions

Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses.

...view full instructions

Assertion: On bringing a positively charged rod near the uncharged conductor, the conductor gets attracted towards the rod.

Reason: The electric field lines of the charged rod are perpendicular to the surface of the conductor.

A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.

C
If the Assertion is correct but Reason is incorrect.

D
If both the Assertion and Reason are incorrect.

Solution

Though the net charge on the conductor is still zero but due to induction the negatively charged region is nearer to the rod as compared to the positively charged region. That is why the conductor gets attracted towards the rod
Question 7
4 / -1

Two parallel, large and thin metal plates have equal surface charge densities (σ = 26.4 x 10^-12 C/m²) of opposite signs. The electric field between these plates is

A
1.5 N/C

B
1.5 x 10^-10 N/C

C
3 N/C

D
3 x 10^-10 N/C

Solution
Question 8
4 / -1

When a conductor is placed in an electric field; its free charge carriers adjust itself in order to oppose the electric field. This happen until

A
Both the fields cancel out each other

B
Induced field become more than external field

C
External field reach the maximum value

D
Induced field reach the maximum value

Solution

When an external electric field is applied to the conductor, the free electrons in the conductor move in an opposite direction to that of the applied electric field.

This movement of electrons induces another electric field inside the conductor which opposes the original external electric field.

This continues until the induced electric field cancels out the external field.
Question 9
4 / -1

The electric field inside a dielectric decreases, when it is placed in an external electric field. This happens due to ________

A
Electrostatic shielding.

B
Polarization.

C
Electrostatic repulsion between atoms.

D
Electrostatic attraction between atoms.

Solution

The external electric field polarizes the dielectric and an electric field is produced.

The net electric field inside the dielectric decreases due to polarization.
Question 10
4 / -1

The magnetic field inside a toroidal solenoid of radius R is B. If the current through it is doubled and its radius is also doubled keeping the number of turns per unit length the same; magnetic field produced by it will be:

A
B/2

B
B/4

C
B

D
2B

Solution

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Physics Test 274

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Physics Test 274

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Question 1

9 x 109

9.9 x 1010

99 x 1010

5.4 x 1010

Solution

Question 2

Connecting two in series and one in parallel

Connecting two in parallel and one in series

Connecting all of them in series

Connecting all of them in parallel

Solution

Question 3

600 μC

700 μC

250 μC

1300 μC

Solution

Question 4

First flows from A to B and then, from B to A

First flows from B to A and then, from A to B

Always flows from B to A

Always flows from A to B

Solution

Question 5

If both the Assertion and Reason are incorrect.

If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.

If the Assertion is correct but Reason is incorrect.

Assertion is false, Reason is true

Solution

Question 6

If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.

If the Assertion is correct but Reason is incorrect.

If both the Assertion and Reason are incorrect.

Solution

Question 7

1.5 N/C

1.5 x 10-10 N/C

3 N/C

3 x 10-10 N/C

Solution

Question 8

Both the fields cancel out each other

Induced field become more than external field

External field reach the maximum value

Induced field reach the maximum value

Solution

Question 9

Electrostatic shielding.

Polarization.

Electrostatic repulsion between atoms.

Electrostatic attraction between atoms.

Solution

Question 10

B/2

B/4

B

2B

Solution

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9 x 10⁹

9.9 x 10¹⁰

99 x 10¹⁰

5.4 x 10¹⁰

1.5 x 10^-10 N/C

3 x 10^-10 N/C