Van de Graaff Generator Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. What is meant by an electrostatic generator?

Ans. An electrostatic generator is an electrical generator used to produce static electricity. It is also known as an electrostatic machine that produces electricity at high voltage and low current.

Ques. On which principle does the Van de Graaff generator work?

Ans. The principle of the Van de Graff generator is that a large amount of charge can be placed on the outer surface of a spherical shell to increase its potential to a very high value by transferring some charge to it.

Ques. The Van de Graff generator was invented by

1. Sir Issac Newton
2. Albert Einstein
3. James Clerk Maxwell
4. Robert J. Van de Graaff

Ans. The correct answer is d. Robert J. Van de Graaff

Explanation: Robert J. Van de Graaff invented in 1929 invented Van de Graff generator.

Ques. A Van de Graff generator produces

1. large resistance and less voltage
2. large voltage and less current
3. large current and less voltage
4. large current and large resistance

Ans. The correct answer is b. large voltage and less current

Explanation: A Van de Graff generator produces large voltage and less current. The large voltage is due to the large size of its dome because it can store more charge. Less current is due to that a Van de Graff generator offers high resistance.

Ques. What is Van De Graaff Generator?

Ans. A Van de Graff generator is an electrostatic high-voltage generator that can supply a voltage of a few million volts.

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Short Answers Questions [2 Marks Questions]

Ques. How can you Prevent Corona Discharge?

Ans. The phenomenon when a high electric field due to the accumulation of charge on a conductor ionized the air molecules surrounding the conductor is known as Corona discharge. It can be reduced by

• Increasing Conductor Size
• Increasing conductor spacing
• Using corona ring
• Using bundled conductors

Ques. What is the process by which a Van de Graaff becomes positively charged?

Ans. The process by which the metal sphere of a Van de Graff generator becomes positively charged is known as the Triboelectric effect. 

Ques. How can the whole charge of a conductor be transferred to another isolated conductor?

Ans. The whole charge of a conductor can be transferred to another isolated conductor through a process known as electrostatic induction. When a charged conductor is brought near an uncharged isolated conductor, an equal amount of opposite charge is induced in the isolated conductor due to the redistribution of charges on it through the electric field of the charged conductor.

Ques. What is an electric field?

Ans. The region or space around a charged body within which its influence can be felt by another small charge is known as the electric field.

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Long Answers Questions [3 Marks Questions]

Ques. Why does hair stand up when touching a Van de Graaff?

Ans. When we touch the metal sphere of a van de Graff generator our hair stands up due to the principles of static electricity.

• The electrons from our body are transferred to the positively charged metal sphere of the device.
• The excess positive charge on the metal sphere repels the positive charge of our body.
• Hair that is made of strands with individual positive charges repel each other due to their like charges.
• The hair of our heads tries to move as far away from each other as possible, causing them to stand up and spread out.

Ques. What are the limitations of the Van De Graaff Generator?

Ans. The followings are the limitations of the Van de Graff generator

• It can accelerate only charged particles but not uncharged particles.
• Charges move along one route only and do not follow multiple paths.
• Only a small output current is obtained by a Van de Graff generator which is not suitable for equipment that requires a high current.
• The charging rate is very slow.

Ques. What are the components of the Van De Graaff Generator?

Ans. The components of the Van de Graff generator are

• A large conducting spherical shell
• An insulated stand
• A belt made of insulating fabrics
• Two pulleys
• An electric motor
• A high-voltage rectifier
• Two spray combs made of the metallic needle

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Very Long Answers Questions [5 Marks Questions]

Ques. Explain the construction and working of the Van de Graaff generator.

Ans. A Van de Graaff generator consists of a hollow metal sphere mounted on top of an insulating column. 

• There is a belt that is driven by a motor made of non-conductive material like fabric or rubber. 
• This belt is connected between two pulleys, one is present at the bottom, and the other is at the top. 
• The pulley at the bottom is connected to the low-voltage supply. 
• When the motor is switched on, it drives the belt and moves it upward. 
• The belt rubs against a pair of brushes made of some conducting material while moving. 
• These brushes are connected to the power supply and transfer charge to the belt. 
• This phenomenon of rubbing between brushes and belts is known as the triboelectric effect. 
• Due to this effect, the belt become charged. When the charged surface of the belt comes close to the metal terminal at the top, it induced an opposite charge on it. 
• These two opposite charges start attracting each other and the transfer of charge takes place between the belt and the metal sphere. 
• This process of charge transfer continues until a significant amount of charge accumulates on the metal sphere. 
• This charge buildup can create very high voltage on the metal sphere. 
• This high potential can be used for various applications, such as accelerating particles for nuclear disintegration.

Ques. What are the applications of the Van de Graaff generator?

Ans. Some applications of the Van de Graff generator are

• It is used to accelerate charged particles such as protons and ions in nuclear physics research.
• It is used in creating high-voltage electric fields that help in confining and heating plasma during fusion experiments.
• It can be used to generate X-rays for the study of X-ray diffraction or material analysis.
• It is used in laboratories of schools or colleges to demonstrate various principles of electricity, static charge, and voltage.
• Van de Graaff generators can be used for electrospinning.

Ques. What are the precautions and safety measures needed to be taken while accessing the Van De Graaff Generator?

Ans. The followings are the precautions and safety measures needed to be taken while accessing the Van de Graff Generator

• Only those who have proper training and a good understanding of electrical safety be allowed to operate it.
• This device should be placed on a non-conductive, dry, and isolated surface to prevent any accidental discharge.
• To prevent the buildup of static charge and to provide a safe discharge path the generator should be properly grounded.
• Those who work near the Van de Graff generator should wear rubber gloves and non-conductive footwear.
• To avoid electrical shocks, all metal objects should be like jewellery and other conductive materials kept away from the device.

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