Science questions in short. [3 marks ]

In first case, a charged balloon repels another charged balloon as both have like charges and like charges repel each other. In second condition, an uncharged balloon gets attracted towards a charged balloon because the charged balloon induces opposite charge on it. This process of inducing charge on an uncharged body by bringing it close to a charged body is known as induction.

During a thunderstorm, the air currents move upwards and the water droplets move downwards. And this caused the separation of charge due to this vigorous motion. As a result of this process, the positive charges collect near the upper edge and the negative charges accumulate near the lower edge of the cloud and also near the ground. As the charge gets accumulated, its magnitude becomes very large. Water droplets in the air act as a conductor of this charge. These charges flow to meet, thus producing strikes of lightning as shown in the figure below.

This occurs due to electrostatic charge means the charges which are at rest. When the comb is rubbed with hair it gets charged, and when the comb is brought near the neutral paper strips than within the papers strips, the electrons get either repelled or attracted according to whether the comb has a negative or a positive charge. This makes the paper strips have an unlike charge in the direction of the comb, and makes them to get attracted towards the comb as shown in the figure below.

The formation of clouds involves friction between water droplets in the atmosphere. The friction charges the particles in the atmosphere. Among the positive and negative charges, the negative charges accumulate at the bottom of the cloud and the positive charges at the top. As the accumulation of the charges increases, the cloud will induce positive charges on the ground nearby. As the number of charge increases, the negative charges on the cloud tend to make a path towards the ground, and it results in a narrow streak of electrical discharge, which we call lightning. The figure below shows the lightning.

A lightning rod, also known as a lightning conductor, is a building safety device designed for the sole purpose of stopping lightning from hitting a building. It is made of good conductors like copper and permits the lightning bolt's electrical energy to go harmlessly to ground where it belongs. All tall buildings now have lightning conductors. The figure below shows the lightning conductor.

In normal condition the number of protons and electrons in any atom is equal. But every atom has got an affinity for getting excess electrons. Due to it when two bodies are brought in contact with each other, the body which has a greater affinity for electron collect electrons from other body and gets charged negatively this is called as electrification by friction.Example: When a glass rod is rubbed with silk, Silk gets negatively charged and glass rod gets positively charged. As shown in the figure below.

When a positive charge is kept near a negative charge then there will be an attraction between the positive and negative charge because unlike charges attract each other. For example: When an ebonite rod and glass rod are brought close to each other there will be an attraction as shown in the figure below. A charged glass rod attracts a charged plastic straw.

It happens because the television screen or computer monitor are charged and have static charges accumulated on them and when we touch them with our hands which are uncharged, the charges transfer through our hands and we get a slight shock.

No, there will not be any lightning at all because charge separation cannot take place in conductors.So, all the charges collected at the clouds will continuously transfer through air, i.e. charge will not accumulate on cloud and so, there will be no lightning.

No, scientists have tried lots of different ways of predicting earthquake but none have been successful so far. They have a pretty good idea of where an earthquake is most likely to hit but they still cannot tell exactly when it will happen.

The electric charges generated by rubbing are static electric charges. These electric charges remain bound on the surface of the charged object. When a glass rod is rubbed with silk, some of the electrons from the glass atoms are transferred to silk. Due to the deficiency of electrons in the glass atoms, it becomes positively charged. Whereas the silk has acquired electrons, it becomes negatively charged. Iron rod is a conductor. As soon as we charge an iron rod by rubbing with another material, the electric charge flow through our hand and body and flows into the earth. As a result, the iron rod remains un-charged by rubbing, if held by hand.

The crackling sound and the tiny sparks of light re-noticed due to electric discharge between sweater and body. The sweater is made up of wool and the shirt we wear is made up of cotton blended with some synthetic fibres. When we take out the sweater the friction is developed and the transfer of electrons take place from shirt to sweater, this results in the building of electric potential. When enough potential has been accumulated while taking off the sweater it discharges and transfer of electrons take place. This transfer of electrons forms spark and let out sound energy and heat energy. Thus we hear the crackling sound and see the tiny sparks of light in the dark room.

Lightning will not strike the building because charge separation cannot take place in conductors and so, all the lightning falling on the building will reside on the surface of the building and will pass to the ground through the conductor. So, there is no need of installing any lightning conductor because all the work of a lightning conductor is done by the conducting material itself.

There are mainly two type of charges namely Positive Charge and Negative Charge.
Positive Charge: When an electron is removed from the object it makes an object deficient of electrons and the object acquires the positive charge.
Negative Charge: When electrons are added to an object it gives the excess of electrons to it and makes it negatively charged.
When the number of positive and negative charges are equal than the object is said to be neutral.

An Electroscope is an instrument which can be used to detect whether a body is charged or not. The following figure shows the simple Electroscope.
Construction: An electroscope has a brass rod passing through a tight fitting cork in a glass bottle. A pair of thin gold leaves is attached to the lower end of the brass rod. To protect the gold leaves from an external electric charge the lower half of the bottle is lined with tin foil which is ‘earthed’ by connecting it to the table. Working: When a charged rod is touched to the metal disc, the charge is transferred to the gold leaves and they diverge.