Electric Charges and Fields Test

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Electric Charges and Fields Test - 39

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Weekly Quiz Competition

Question 1
1 / -0

An electric filament bulb can be worked from

A
DC supply only

B
AC supply only

C
Battery supply only

D
All above

Solution

An electric filament bulb can be worked from
1. AC Current.
2. DC Current.
3. Battery current.

Option D is correct.
Question 2
1 / -0

The safety fuse should have

A
high resistance and high melting point

B
high resistance and low melting point

C
low resistance and high melting point

D
low resistance and low melting point

Solution

The safety fuse should have high resistance and low melting point.

Option B is correct.
Question 3
1 / -0

Opening up of strips of an electroscope is an indication of:

A
Proximity of a conductor.

B
Proximity of a charged body.

C
Proximity of an uncharged body.

D
Earth connection.

Solution

When a charged body comes close to an electroscope, charges are induced to the electroscope. These charges flow down to the metal strips which open up due to repulsion for having similar charges.
Question 4
1 / -0

A charge of $$1 \mu C$$ is divided into two parts such that their charges are in the ratio of $$2 : 3$$. These two charges are kept at a distance $$1 m$$ apart in vacuum. Then, the electric force between them (in N) is:

A
$$0.216$$

B
$$0.00216$$

C
$$0.0216$$

D
$$2.16$$

Solution

Ratio of charges $$= 2 : 3$$
$$\therefore \quad { q }_{ 1 }=\dfrac { 2 }{ 5 } \times 1\mu C$$ and $${ q }_{ 2 }=\dfrac { 3 }{ 5 } \times 1\mu C$$

Electrostatic force between the two charges:
$$F=\dfrac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \dfrac { { q }_{ 1 }{ q }_{ 2 } }{ { r }^{ 2 } } $$
$$=\dfrac { 9\times { 10 }^{ 9 }\times 2\times { 10 }^{ -6 }\times 3\times { 10 }^{ -6 } }{ 5\times 5\times { 1 }^{ 2 } } $$
$$=2.16\times { 10 }^{ -3 }N$$
Question 5
1 / -0

In winter season, a mild spark is often seen when a man touches somebody else's skin. Why?

A
Due to lack of humidity and rubbing with clothes, charge accumulate on human body which is discharged via sparking

B
Due to cold, electrostatic charge on body finds a lower resistance path to the skin of other's body

C
The static charge on sweaters worn by the two persons is different, hence discharge through sparking occurs

D
Similar to the lightning, extremely high potential exists on both the bodies and hence they discharge through sparking

Solution

Due to friction between clothes and skin, electrostatic charge is built up on skin. Hence, electrical discharge may occur when a man touches somebody else. This phenomenon is more significant in winters because due to low humidity, charge has a tendency to stay longer on the body.
Question 6
1 / -0

The figure shows two situations in which a Gaussian cube is placed in an electric field. The arrows and values indicate the directions and magnitudes (in $$\displaystyle N-{ { m }^{ 2 } }/{ C }$$) of the electric fields.What is the net charge (in the two situations) inside the cube?

A
(1) negative, (2) positive

B
(1) negative, (2) zero

C
(1) positive , (2) positive

D
(l) negative, (2) negative

Solution

Given the 2 situation in which a Gaussian cube sits in the electric field. the magnitudes & direction of field line are given in the figure we have to find net charge in both situation.
Hear we use Gauss's law,
$$\phi =\cfrac { q }{ { \varepsilon }_{ 0 } } $$
so,$$q=\phi \times { \varepsilon }_{ 0 }$$
q=charge enclosed within the Gaussian surface.
$${ \varepsilon }_{ 0 }=$$permeability in air.
$$ \phi =flux\quad$$ through a surface.
As $$ \phi =$$electric field $$\times$$ area of Gaussian surface.
since area of Gaussian surface is same in both the case;so the net charge depend on the net flux through surface.
flux in case(1) : lines coming out -lines entering.
$$=6+7-2-15-7-8$$
$$=-ve$$
so; charge is (1) situation is negative.
in case (2), net flux$$=9+3-2-6-7-5$$
$$=-ve$$
so charge in $$ -ve$$ in case(2)
so; the answer is both negative charge.
Question 7
1 / -0

In the thunderstorm, the charges accumulate near the upper edges of clouds are

A
negatively charged

B
positively charged

C
neutral

D
none of these

Solution

We have to find the nature of charges on upper edges of clouds in a thunderstorm, the air currents move upwards while the water droplets move downward. This vigorous movement causes separation of charges. This leads to the positive charges collected near the upper edges of clouds and the negative charges to accumulate near the lower edges of the clouds.
Question 8
1 / -0

When a comb is rubbed with hair, it attracts paper bits. Choose the right explanation:

A
Bits of paper gets attracted due to gravitational force

B
Due to electromagnetic effect, bits of paper are attracted

C
Comb gets charged by friction and attracts bits of paper

D
None of these

Solution

When comb is rubbed to hair, it induces negative charge due to friction. When it is brought close to paper bits, they get polarized and the positive part sticks to the comb due to electrostatic attraction.
Question 9
1 / -0

Two bodies have equal charge $$q$$, where each is charged with two electrons. One electron is transferred from the first body to the second so that one body has one excess electrons and other has three excess electrons while maintaining the distance between the charges. Which of the following statements are correct?
I.The amount of electrostatic charge has decreased
II.The electrostatic force between the pith balls has decreased
III.Both the electrostatic charge and force have decreased

A
I only

B
II only

C
I and III only

D
II and III only

E
I, II, and III

Solution

The electrostatic force between two charges $$q=2e$$ and $$q=2e$$ , separated by a distance $$r $$ is ,
$$F=K\dfrac{2e\times 2e}{r^{2}}=K4e^{2}/r^{2}$$ ,
after transfer of charge , new charge distribution is $$q=e$$ and $$q'=3e$$ , now ,electrostatic force between them will be ,
$$F'=K\dfrac{e\times 3e}{r^{2}}=K3e^{2}/r^{2}$$ ,
this implies $$F'<F$$ , force between them decreases.
Total charge before transfer $$=2e+2e=4e$$
and total charge after transfer $$=e+3e=4e$$ ,
It remains the same .
Question 10
1 / -0

Identify which of the above shown graphs represents the force between two electrons Vs distance between them?

A
Graph A

B
Graph B

C
Graph C

D
Graph D

E
Graph E

Solution

The electric force between two electrons is given by ,
$$F=\dfrac{1}{4\pi\varepsilon_0}.\dfrac{e\times e}{r^{2}}$$
where $$r$$ is the distance between two electrons ,
therefore , $$F\propto 1/r^{2}$$ , this relation is denoted by graph $$A$$ .

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Electric Charges and Fields Test - 39

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Electric Charges and Fields Test - 39

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Question 1

DC supply only

AC supply only

Battery supply only

All above

Solution

Question 2

high resistance and high melting point

high resistance and low melting point

low resistance and high melting point

low resistance and low melting point

Solution

Question 3

Proximity of a conductor.

Proximity of a charged body.

Proximity of an uncharged body.

Earth connection.

Solution

Question 4

$$0.216$$

$$0.00216$$

$$0.0216$$

$$2.16$$

Solution

Question 5

Due to lack of humidity and rubbing with clothes, charge accumulate on human body which is discharged via sparking

Due to cold, electrostatic charge on body finds a lower resistance path to the skin of other's body

The static charge on sweaters worn by the two persons is different, hence discharge through sparking occurs

Similar to the lightning, extremely high potential exists on both the bodies and hence they discharge through sparking

Solution

Question 6

(1) negative, (2) positive

(1) negative, (2) zero

(1) positive , (2) positive

(l) negative, (2) negative

Solution

Question 7

negatively charged

positively charged

neutral

none of these

Solution

Question 8

Bits of paper gets attracted due to gravitational force

Due to electromagnetic effect, bits of paper are attracted

Comb gets charged by friction and attracts bits of paper

None of these

Solution

Question 9

I only

II only

I and III only

II and III only

I, II, and III

Solution

Question 10

Graph A

Graph B

Graph C

Graph D

Graph E

Solution

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