Electric force - class-XII

There are 2 types of electrical charges - positive and negative - are said to be opposite types of charge. Consistent with our fundamental principle of charge interaction, a positively charged object will attract a negatively charged object. Oppositely charged objects will exert an attractive influence upon each other. In contrast to the attractive force between two objects with opposite chargess, two objects that are of like charge will repel each other. That is, a positively charged object will exert a repulsive force upon a second positively charged object. This repulsive force will push the two objects apart. Similarly, a negatively charged object will exert a repulsive force upon a second negatively charged object. Objects with like charge repel each other.
Therefore, Like charges repel, while unlike charges attract each other.

Answer is A.

Static electricity is created when two objects are rubbed together, causing an object to give up or gain electrons. The electric charges that are created do not depend on the size of the objects. Therefore, when two bodies are rubbed together, both the bodies transfer electrons to and fro between the bodies and they obtain equal and opposite charges. The body that gives away electrons, gains positive charge and the body that obtains electrons gains negative charge.

Answer is B.

When two bodies are rubbed together, there is transfer of electrons because of friction.
Hence, two uncharged bodies on rubbing, gets equal and opposite charges.

Since the rod which was brought closer was negatively charged the induced charge acquired by the spheres will be positive. 

Electrostatic force is the phenomenon that results from slow-moving or stationary electrical charges. Specifically, electrostatic force is the physical reaction that holds together the electromagnetic field created by subatomic particles, such as electrons and protons. In order for electrostatic forces to remain cohesive, these particles need to independently maintain both positive and negative charges and react to each other accordingly. 
When a balloon is rubbed with a cloth, the electrons from the atoms of the cloth enter the atoms of the balloon and the number of electrons in the atoms of balloon becomes more than the number of protons. Because of that, there is a negative charge in the balloon, and in the cloth the number of electrons in its atoms become less than the number of protons, so it's positively charged.
Therefore, due to this electrostatic force, the balloon sticks to the wall.

Answer is B.

The statement is false because only unlike poles attract each other. Like poles repel each other.

Answer is B.

By symmetry, the charge will distribute evenly over the surface of the bubble. Because like charges repel, they want to move even further apart, the only which way is outward, taking the soap surface with them. Of course, the increase in restoring force of the soap film (surface tension) will at some point be equal and opposite to the electrostatic force, resulting in a new (larger) equilibrium radius.
This will happen to both positive and negatively charged bubbles because of the ionic similarity.
Hence, when the soap bubble is given a negative charge, then its radius will increase.

Lightning is a sudden electrostatic discharge during an electrical storm between electrically charged regions of a cloud, between that cloud and another cloud, or between a cloud and the ground.

Negative electric charge often resides on the surface of metal of car. When you touch the car, electrostatic discharge occurs via your body and you get a mild spark.

(d) is based on Joule's Law.

An attractive property is develop in the comb due to friction. The comb on rubbing over dry hairs is aid to be charged.

The stationary charge (i.e static electricity) is produced by friction.

If a ordinary glass rod is rubbed on the silk cloth is brought near bits of paper, it is found that they have acquired the attractive property. The glass rod get charged on rubbing.

When negatively charged atom is attracted towards positively charged atom, it is known as electrostatic attraction.

When two positively or two negatively charged electrons come closer to each other then they repel from each other. Then it is known as electrostatic repulsion.

Newton's law : force $F=ma$  where m=mass and a=acceleration

Coulomb's Law : $\dfrac{kq _1q _2}{r^2}$
It depends on both magnitude of charges and distance between them. 

Electrostatic : when the charges are under action of electric forces. 

The Coulomb law is the force between two charges $q _1$ and $q _2$ when the separation between them is $r _{12}$. 

We know that Coulomb's force, $F=\frac{1}{4\pi \epsilon _0} \frac{q _1q _2}{r^2}$

The Coulomb's constant, $k=\dfrac{1}{4\pi\epsilon _0}=\dfrac{1}{4\pi\times (8.85\times 10^{-12})}=9\times 10^9$

When we wear nylon dresses during winter then there is electrostatic current which gets produced due to contact with out body.

When negative charges is created in the comb by rubbing it with hair and pieces of paper are exposed to the electric field created by the charge, the part of paper closer to the comb will be positively charged due to electromagnetic induction, and the farther would be negatively charged, causing the paper to be attracted to the comb.

By Coulomb's law, the force between two charges is $F=k \dfrac{q _1q _2}{r^2}=(9\times 10^9)\times \dfrac{5\times 10}{(0.5)^2}=18\times 10^{11} N$

The above statement is false. Unlike charges attract each other. A proton attracts an electron.

There are two types of charges, positive and negative. Same type of charges (two positive or two negative) repel each other, while unlike charges (one positive and one negative) attract each other.

The like charges repel and unlike charges attract each other, hence option A is correct answer.

This is a geometric series problem where the charge on the conductor after n operations is q_n = q(1 + (q/Q) + (q/Q)^2 + ... + (q/Q)^(n-1)). As n approaches infinity, this converges to q / (1 - q/Q) = Qq / (Q - q).

$\overrightarrow{E _a}=\cfrac{h _E}{ra^3}=\cfrac{h _E}{1^2+2^2+3^2}(1\hat{i}+2\hat{j}+3\hat{k})\ \overrightarrow{E _a}=\cfrac{h _E}{14^{3/2}}(1\hat{i}+2\hat{j}+3\hat{k})\ \overrightarrow{E _b}=\cfrac{ha}{r _b^2}\overrightarrow{r _b}=\cfrac{h _E}{(1^2+1^2+1^2)}^{3/2}(1\hat{i}-1\hat{j}+1\hat{k})\=\cfrac{h _E}{3^{3/2}}(1\hat{i}-1\hat{j}+1\hat{k})\ \overrightarrow{E _c}=\cfrac{h _E}{r _c^2}\overrightarrow{r _c}=\cfrac{h _E}{(2^2+2^2+2^2)^{3/2}}(2\hat{i}+2\hat{j}+2\hat{k})$

Object with same nature of charges repel each other i.e, positive charges repel positive charge and negative charges repel negative charge.

The maximum electric field (dielectric strength) for an air-filled parallel plate capacitor is E = V / d = (Q / C) / d = Q / (epsilon_0 * A). Rearranging for area gives A = Q / (epsilon_0 * E). Substituting the values: A = 12 * 10^-6 / (8.85 * 10^-12 * 3 * 10^6) = 12 * 10^-6 / (26.55 * 10^-6) = 12 / 26.55 is approximately 0.45 m^2.

A capacitor consists of two conductors separated by an insulator. In a DC circuit, it blocks current once charged. In an AC circuit, it allows current to flow due to the changing electric field, but it is still physically an insulator between the plates.

Four charges $+Q$, $-Q$, $+Q$, $-Q$.

There are two charges $+2\mu C$ and $-3\mu C$. The ratio of forces acting on them will be $F=\dfrac { { q } _{ 1 }{ q } _{ 2 }K }{ { r }^{ 2 } } $

Force of attraction between two point charges $Q$ and $-Q$ separated by $d$.

Two lithium nuclei in a lithium vapor can combine only if vapor is heated to a very high temperature. so that the nuclei acquire high kinetic energy to penetrate the coulomb barrier. The vapor is also compressed to a very high pressure.

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. 

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.

If charge 1 is positive and charge 2 is negative, then charge 1 and 2  will attract. As charge 2 and 3 repels so charge 3 should be negative. Since charge 3 and 4 attracts so charge 4 should be positive. Thus, charge 1 and 4 both are same charge so they will repel. If you take charge 1 is negative and 2 is positive similarly you get 4 is negative so 1 and 4 both have same charge. 

Electric force can be either attractive or repulsive .

Charge on $A^{+}$ sphere $=-3$ $uC$

The radius of soap bubble increases due to inter-electronic repulsion.
Note that, the bubble may also explode if excess charge is large enough.

Two bodies having same nature of charge repel each other.

Attraction between 1 and 2, 2 and 4, and 4 and 1 implies that 1, 2, and 4 must have different charges or one is neutral. Repulsion between 2 and 3, and 4 and 5, implies 2 and 3 have the same charge, and 4 and 5 have the same charge. If 1 is neutral, it attracts both positive and negative charges, which is consistent with the observations.

If we bring small bits of paper near a rubber (or plastic) comb, it is found that the comb does not attract the bits of paper. But if the same comb is first rubbed on dry hairs and then it is brought near the paper pieces, it attracts them.

There are 2 types of electrical charges - positive and negative - are said to be opposite types of charge. Consistent with our fundamental principle of charge interaction, a positively charged object will attract a negatively charged object. Oppositely charged objects will exert an attractive influence upon each other. In contrast to the attractive force between two objects with opposite chargess, two objects that are of like charge will repel each other. That is, a positively charged object will exert a repulsive force upon a second positively charged object. This repulsive force will push the two objects apart. Similarly, a negatively charged object will exert a repulsive force upon a second negatively charged object. Objects with like charge repel each other.
Hence, the statement is false.

Like charges repel each other whereas unlike charges attract each other.

Answer is A.

When two like charges are brought closer, they repel and when two unlike charges are brought closer, they attract each other.
Hence, unlike charges attaract each other and the statement is true.

The radius of soap bublle increases because of outward force acting on the bubble due to charging

Static electricity is produced when a suitable combination of substances (e.g., glass rod and silk, ebonite rod and cat's skin, sealing wax and wool) are rubbed together and get electrified due to friction.

Rubbing the glass rod with the silk makes it lose electrons, so glass rod becomes positively charged. When a negatively charged ebonite rod is brought near the glass rod it attract each other as unlike charges attract each other.