The Van de Graaff generator was invented by American physicist Robert J. Van de Graaff. It is an electrostatic generator. The Van de Graaff Generator is an electric device used to generate extremely high potential differences ranging from a few million to 20 million volts. The Van de Graaff generator currently produces a potential difference of 5 Megavolts. Van de Graaff generators are electrostatic devices that operate primarily on two principles: corona discharge and accumulation of charge on the outer sphere. When we place a grounded object around the output terminal (sphere) of the Van de Graaff generator, the voltage decreases, but the current remains constant. The charges are produced by the friction between two insulating bodies rubbing against each other, and they can’t move on their own (at rest), so they’re static by nature and are called static charges.
There are two main types of Van de Graaff Generators: the first one employs a high-voltage power supply for charging, and the second one utilises belts and rollers for charging. Van de graff generators are used in particle accelerators to generate X-ray beams, as well as in science education and food sterilisation.
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Important Questions with Answers
1. What is an electric field?
An electric field is a force produced by a charge near its surroundings. This force is exerted on other charges when brought to the vicinity of this field.
2. What are the applications of the Van de Graaff generator?
Van de Graaff generators are frequently used as accelerators to generate energetic particles and X-ray beams for nuclear research and nuclear medicine.
3. On which principle does the Van de Graaff generator work?
The Van de Graaff generator works based on the principle of static electricity. This states that when a charged conductor comes into contact with a hollow conductor, all charges from the inner conductor are transmitted to the surface of the outer conductor. This is regardless of how much charge is already present on the outer shell.
4. What is the process by which a Van de Graaff becomes positively charged?
The Van de Graaff generator produces a positive charge on its dome by removing electrons. Because static electricity is a non-contact force, a person does not need to touch the dome to begin feeling the effects. Any charged particle in the electric field surrounding the dome will be affected by this force.
5. Why does hair stand up when touching a Van de Graaff?
Each individual hair has the same net charge as the rest of the fur and the dome. Since like charges repel, the hairs are pushed away from each other and the similarly-charged dome, causing them to stand up.
6. The Van de Graff generator was invented by ________.
- Albert Einstein
- Robert J. Van de Graaff
- Sir Issac Newton
- James Clerk Maxwell
Answer: B. Robert J. Van de Graaff
Explanation – The Van de Graaff generator was designed by Robert Jemison Van de Graaff in 1929.
7. A Van de Graff generator produces _____________.
- large voltage and less current
- large resistance and less voltage
- large current and large resistance
- large current and less voltage
Answer: A. large voltage and less current
Explanation: Van de Graff generators produce large voltages and less currents. A Van de Graff generator is an electrostatic generator that creates very high electric potentials. At low current levels, it produces very high voltage direct current electricity.
8. What is meant by an electrostatic generator?
An electrostatic generator, or electrostatic machine, is an electrical generator that produces static electricity, or electricity at high voltage and low continuous current.
9. What factors limit the maximum voltage obtained in a Van de Graaff generator?
Several sources discuss the field intensity outside the dome as a limiting factor on the highest voltage. That can be generated on a Van de Graaff generator. There are also references to possible dielectric breakdown along the belt itself.
10. Why are there charged particles on the dome of the Van de Graaff generator?
A Van de Graaff generator removes an electron to generate a positive charge on its dome. Since static electricity is a non-contact force, a person does not have to interact with the dome to experience its effects. This force will act on any charged particle in the dome’s electric field.
11. Define the insulator with an example.
An insulator is a material that keeps energy, such as electricity, heat or cold, from efficiently transferring through it. Wood, plastic, rubber, and glass are all excellent insulators.
Practice Questions
- What is the difference between a motor and a generator?
- How does the Van de Graaff generator charge by friction?
- Is the human body positively charged or negatively charged?
- Why do Van de Graaff generators shock you?
- Explain the construction and working of the Van de Graaff generator
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