Electric Charges and Fields Test

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Electric Charges and Fields Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

Complete the following statements with an appropriate word /term be filled in the blank space(s).

The force of attraction or repulsion between two charges is given by ......................

A
Gauss's law

B
Kepler's law

C
Coulomb's law

D
Gravitational law

Solution

Coulomb's law: The force exerted by one point charge is proportional to the product of the charge and varies inversely as the sure of the distance separating the charges.
Question 2
1 / -0

The ampere-sec stands for the unit of :

A
Power

B
Current

C
Energy

D
Charge

Solution

Charge is given by the relation, $$q = I*t$$
so its unit is ampere - sec
Question 3
1 / -0

A uniform rod of length l and mass m is free to rotate in a vertical plane about A. The rod initially in horizontal position is released. The initial angular acceleration of the rod is (Moment of inertia of rod about A is $$\frac{ml^{2}} {3}$$

A
$$\frac{3g} {2l}$$

B
$$\frac{2l} {3g}$$

C
$$\frac{3g} {2l^{2}}$$

D
$$\frac{l} {2}$$

Solution

Here $$\tau$$ = $$I\alpha$$

$$\Rightarrow \left (mg\right) \left (\frac{l} {2}\right)$$ = $$\left (\frac{ml^{2}} {3}\right) \left (\alpha\right) \Rightarrow \alpha$$ = $$\frac{3g} {2l}$$
Question 4
1 / -0

Two point charges $$2\ C$$ and $$-6\ C$$ attract each other with a force of $$12\ N$$. A negative charge of $$2\ C$$ is added to each of the above charges, now the force between them is :

A
$$32\ N$$

B
$$8\ N$$

C
$$zero$$

D
$$4\ N$$

Solution

When $$-2C$$ is added to $$2C$$ and $$-6C$$, they become $$0C$$ and $$-8C$$ respectively. Since one of the charges is now zero, the force between them is zero.
Question 5
1 / -0

What happens when some charge is placed on a soap bubble?

A
Its radius decreases

B
Its radius increases

C
The bubble collapses

D
None of these

Solution

The radius of soap bublle increases because of outward force acting on the bubble due to charging
Question 6
1 / -0

The ratio of electric force between two electrons to two protons separated by the same distance in air is:

A
$${10}^{0}$$

B
$${10}^{6}$$

C
$${10}^{4}$$

D
None of these

Solution

$$\cfrac { { F }_{ e } }{ { F }_{ p } } ={ 10 }^{ 0 }=1$$, because force depends only on charges, distance and nature of medium and not type of charge. As all other quantities are same , the ratio will be $$1$$
Question 7
1 / -0

The laws of forces that govern the force between two electric charges were discovered by :

A
Faraday

B
Ampere

C
Ohm

D
Coulumb

Solution

Coulomb stated that the force (F) of attraction or repulsion between two points charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$ is proportional to the product of the magnitude of the two charges, and inversely proportional to the square of the distance of separation between them. i.e., $$ F \propto \dfrac{q_1 q_2}{r^2}$$
Question 8
1 / -0

In a region of space having a uniform electric field $$E$$, a hemispherical bowl of radius $$r$$ is placed. The electric flux $$\phi$$ through the bowl is

A
$$2\pi RE$$

B
$$4\pi {R}^{2}E$$

C
$$2\pi {R}^{2}E$$

D
$$\pi {R}^{2}E$$

Solution

$$\phi =E(ds)\quad \cos { \theta } =E(2\pi { r }^{ 2 })\cos { { 0 }^{ o } } =2\pi { r }^{ 2 }E\quad $$
Question 9
1 / -0

The solid angle subtended by the total surface area of a sphere at the centre is :

A
$$4\pi$$

B
$$2\pi$$

C
$$\pi$$

D
$$3\pi$$

Solution

A steradian is the solid angle subtended at the center of a sphere of radius r by a section of its surface area of magnitude equal to $$ { r }^{ 2 }$$. Since the surface area is $$ 4\pi { r }^{ 2 }$$, there are $$ 4\pi$$ steradians surrounding a point in space.
Question 10
1 / -0

Electric field lines of force

A
exist everywhere

B
exist only in the immediate vicinity of electric charges

C
exist only when both positive and negative charges are near one another

D
are imaginary

Solution

Electric lines of force are imaginary.

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Re-Attempt Weekly Quiz Competition

Electric Charges and Fields Test - 23

Result

Electric Charges and Fields Test - 23

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Question 1

Gauss's law

Kepler's law

Coulomb's law

Gravitational law

Solution

Question 2

Power

Current

Energy

Charge

Solution

Question 3

$$\frac{3g} {2l}$$

$$\frac{2l} {3g}$$

$$\frac{3g} {2l^{2}}$$

$$\frac{l} {2}$$

Solution

Question 4

$$32\ N$$

$$8\ N$$

$$zero$$

$$4\ N$$

Solution

Question 5

Its radius decreases

Its radius increases

The bubble collapses

None of these

Solution

Question 6

$${10}^{0}$$

$${10}^{6}$$

$${10}^{4}$$

None of these

Solution

Question 7

Faraday

Ampere

Ohm

Coulumb

Solution

Question 8

$$2\pi RE$$

$$4\pi {R}^{2}E$$

$$2\pi {R}^{2}E$$

$$\pi {R}^{2}E$$

Solution

Question 9

$$4\pi$$

$$2\pi$$

$$\pi$$

$$3\pi$$

Solution

Question 10

exist everywhere

exist only in the immediate vicinity of electric charges

exist only when both positive and negative charges are near one another

are imaginary

Solution

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