Tag: electric charges and fields

Questions Related to electric charges and fields

Rub a piece of ebonite across a piece of animal fur. What happens?

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. the fur has a slightly positive charge and the ebonite is slightly negative

  2. the fur has a slightly positive charge and the ebonite is also slightly positive

  3. the fur has a slightly negative charge and the ebonite is also slightly negative

  4. the fur has a slightly negative charge and the ebonite is slightly positive

Show answer
Correct Option: A
Explanation:

When a piece of ebonite is rubbed with a piece of animal fur, frictional charging process results in a transfer of electrons between the two objects. Since ebonite has much greater attraction for electrons than animal fur (electron affinity). As a result, atoms of ebonite pull electrons from atoms of animal fur, and as a result, ebonite becomes negatively charged  and animal fur becomes positively charged. 

An imbalance of electric charges within or on the surface of a material is 

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. current electricity

  2. an electromagnetic wave

  3. static electricity

  4. None of these

Show answer
Correct Option: C
Explanation:

Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge. So, this is the definition of static electricity. 

Rub a glass rod with a piece of silk. What happens?

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. the glass has a slightly positive charge and the silk is also slightly positive

  2. the glass has a slightly positive charge and the silk is slightly negative

  3. the glass has a slightly negative charge and the silk is also slightly negative

  4. the glass has a slightly negative charge and the silk is slightly positive

Show answer
Correct Option: B
Explanation:

When a glass rod is rubbed with silk, both gets electrified due to charging by function by rubbing. One of the body acquires negative charge and other positive charge due to shifting of electrons from one body to other. Since silk has greater electron affinity (ability to attract electrons) as compared to glass. So, silk acquires slight negative charge and glass acquires slight positive charge.

A balloon gets negatively charged by rubbing ceilings of a wall.

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. This implies that the wall is positively charged.

  2. This implies that the wall is negatively charged.

  3. This does not imply that the wall is positively charged.

  4. None of these

Show answer
Correct Option: C
Explanation:

A balloon gets negatively charged by rubbing ceilings of wall. But this does not imply that the wall is positively charged. The balloon induces a charge of opposite sign in the ceilings of the wall, causing the ceiling and the balloon to be attracted to each other. The balloon eventually falls because its charge slowly diminishes as it leaks to ground. Some of the charge on the balloon could also be lost due to the presence of positive ions in the surrounding atmosphere, which would tend to neutralize the negative charges on the balloon.

A comb run through ones hair attracts small bits of paper. What happens, if the hair are wet or if it is a rainy day? 

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. The comb does not get charged and it will not attract small bits of paper.

  2. The comb does not get charged but it will attract small bits of paper.

  3. The comb does gets charged and it will attract small bits of paper.

  4. The comb does gets charged but it will not attract small bits of paper.

Show answer
Correct Option: A
Explanation:

Comb gets electrically charged by friction when even through dry hair. It attracts small bits of paper because paper gets polarized in the presence if charged comb resulting in a net force of attraction. When hair is wet, the friction between comb and hair decreases and comb does not get charged. Hence, it may not attract small bits of paper.

A balloon gets negatively charged by rubbing ceilings of a wall. 

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. The balloon sticks to the ceiling forever.

  2. The balloon eventually fall off the ceiling.

  3. The balloon does not stick to the ceiling at all.

  4. The balloon charges the ceiling negatively.

Show answer
Correct Option: B
Explanation:

The balloon is negatively charged on rubbing with the wall means that on rubbing, the balloon collects electrons from the wall and making it negative in respect to the wall and therefore it clings to the wall, while clinging to the wall, the electrons on the balloon leaks off the balloon and eventually leaves. The balloon at the same potential as the wall, thus when the attraction between the balloon and wall is less than the weight of the balloon, the balloon eventually falls off. 

Which of the following charging methods work without ever touching the object to be charged to the object used to charge it?

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. charging by friction

  2. charging by contact

  3. charging by induction

  4. all of these

Show answer
Correct Option: C
Explanation:

When a charge $Q$ is brought near (but not touching) an uncharged conductor, the charge $Q$ induces a charge of opposite polarity on the facing surface of the conductor and the same polarity on the rearer surface. This process of inducing a charge on the conductor without touching is known as charging induction.

Whereas charging by friction and contact work only when the surface of the two object are in contact with each other.

State whether the given statement is True or False :

When silk is rubbed with glass, the silk gets positively charged.

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

When silk is rubbed with glass, glass happens to lose electrons easily, and silk grabs them away from the glass atoms. So, after rubbing the glass becomes positively charged and the silk becomes negatively charged. 

When a body is charged by induction, then the body

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. Becomes neutral

  2. Does not lose any charge

  3. Loses whole of the charge on it

  4. Loses part of the charge on it

Show answer
Correct Option: B
Explanation:

The part of the body nearer to the source charge gets induced charges, opposite in nature to the source charge while the other part gets those of similar nature.Thus no loss of charge.

A polythene piece rubbed with wool is found to have a negative charge of $3.6\times 10^{-7}C.$ Calculate the number of electrons transferred from wool to polythene:

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. $6.25\times 10^{18}$

  2. $2.25\times 10^{12}$

  3. $2.05\times 10^{-18}$

  4. $2.18\times 10^{10}$

Show answer
Correct Option: B
Explanation:

$n=\dfrac {q}{e}=\dfrac {-3.6\times 10^{-7}C}{-1.6\times 10^{-19}C}$

$=2.25\times 10^{12}$
$\therefore 2.25\times 10^{12}$ electrons are transferred from wool to polythene.