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Electrostatic shielding refers to the phenomenon which is perceived when a Faraday cage works in order to block the effects of an electric field. Such a cage helps in protecting the internal contents from the effects of the external field or the impact of an internal field on the exterior environment. The electrostatic field inside a conductor is zero, we use this in order to protect certain objects from high electric fields by placing them inside a hollow conductor. Here we will discuss electrostatic shielding in detail along with some important questions.
Key takeaways: Electrostatic shielding, Faraday cage, Conductor, Electric field, Electrostatic field, Voltage, Electroscopes, Insulators, Induction machine
Read Also: Electrostatic Potential and Capacitance Important Questions
What is Electrostatic Shielding?
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Electrostatic shielding is a method of protecting a particular region of space, or any sensitive building/instrument, from the impact of an electric charge's external field. For example, a high-voltage measuring device, such as CRO, is maintained inside a hollow conductor or cage known as the Faraday cage. According to the practical demonstration of electrostatic shielding, the reality of reserving this instrument within the conductor is that when there is no charge present within it, there is an absence of electric charge inside a closed conductor.
Michael Faraday prepared a big wired cage supported on insulators, and sat inside it with gold leaf electroscopes, which were electric field detectors. Faraday noted no deflection in electroscopes when this cage was charged using an induction machine. He may also sit within the cage safely and pleasantly. As a result, hollow conductors serve as a shield against powerful electric fields for individuals and equipment. These hollow conductors, also known as Faraday cages, are used to prevent electric charges from accumulating in one location by producing an electric field beyond their immediate vicinity, encircling the charges with a Faraday cage, and connecting this cage to the Earth.
Applications of Electrostatic Shielding
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The meaning of electrostatic shielding is to protect a place from risks such as an external electric field. Let's have a look at some electrostatic shielding applications:
Electrostatic Shielding in Cars: It is safe to sit inside an automobile during a lightning storm because the car's metallic body acts as an electrostatic shield.
Electrostatic: Shielding is a method used in the cables that carry audio signals in order to protect them from external interference, such as an electric field produced by air electricity or electric sparks.
Electrocution: Linemen wear Faraday cage suits to protect themselves from being killed by an electric shock or electrocution.
Elevators in buildings operate as an electrostatic shield, shielding cell phones, radio, and audio transmissions.
The coaxial cables present in the exterior conductor are connected to the ground to supply electrostatic shielding to the signals passed by the central conductor.
Read more: NCERT Solutions for class 12 physics chapter 2- Electrostatic potential and capacitance
What is Faraday Cage?
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The Faraday cage is a type of enclosure designed to keep external electric fields out of conductive materials. Faraday shield is another name for it. Faraday's cage was invented by Michael Faraday in the year 1800. He discovered that when he charged the metal cage, which works as an electrical conductor, the charges appeared just on the surface and had no effect on the interiors. On a larger scale, he lined a chamber in metal foil, permitting high-voltage discharges from an electrostatic generator. He utilized an electroscope, a device that detects electric charges, to validate his idea that the outer surface of the metal foil was conducting current while the inside of the room was empty of electric charges.
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Working of Faraday Cage
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Faraday cages have a cage-like look because they are made of fine metal mesh and chain-like fences that come in a variety of sizes and shapes. The cage may contain electrostatic charges and electromagnetic fields, distributing them throughout the outside of the material on which it is utilized. The charges on the outer surface are distributed in such a way that they cancel with the charges on the interior.
Applications of Faraday Cage
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Some of the applications of the Faraday cage are as follows:
- MRI scanning rooms: The rooms are designed to prevent the mixing of extraneous radio frequency signals with data from the MRI equipment.
- Microwave ovens: The mechanism works with the Faraday cage as its basis, such that electromagnetic energy inside the oven is restrained and the exterior behaves as a radiation barrier.
- They are used in analytical chemistry to decrease noise while performing delicate experiments.
Read more: Magnetic Field in A Solenoid Formula
Why We Earthed the Cage?
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The cage is generally earthed or grounded because if it is not, electrons will disperse in such a way that the interior wall of the cage will acquire an opposite charge to that internal charge. As a result, the outer wall will have the opposite charge as the inside wall.
Following the grounding of the cage, the extra charge created around it, drains to the earth, and there is no external field. So this was the situation if we wanted to drop the charge. However if we want to keep something within the cage, it should not be earthed.
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Things to Remember
- Electrostatic shielding is referred to as a method of protecting a particular region of space, or any sensitive building or instrument, from the impact of an electric charge's external field.
- Electrostatic shielding in cars is safe to sit inside an automobile during a lightning storm because the car's metallic body acts as an electrostatic shield.
- The Faraday cage is a type of enclosure designed to keep external electric fields out of conductive materials.
- Faraday shield is another name for it. Faraday's cage was invented by Michael Faraday in the year 1800.
- Faraday cages are used in analytical chemistry to decrease noise while performing delicate experiments.
Previous Year Questions
- Electric field at centre O of semicircle of radius a having linear charge density λ given as….[NEET 2000]
- Energy per unit volume for a capacitor having area A and separation d kept at potential difference V is given by….[NEET 2001]
- The electric potential at point A, midway between the two charges +q and +q, is….[NEET 2011]
- If potential (in volts) in a region is expressed as V(x, y , z) = 6xy - y + 2yz, the electric field (inN/C) at point (1,1,0) is…..[NEET 2015]
- In the given network, the value of C, so that an equivalent capacitance between A and B is 3μF, is….[KCET 2011]
- The capacitance of combined drop increases..[KCET 1996]
- The ratio of the surface density of charge of each small drop with that of the big drop is...[KCET 2002]
- SI unit of permittivity is ...........[KCET 2004]
- If the speed of sound in air is 340ms−1, the distance between the cliffs is ..........[KCET 2004]
- The system of 3 charges will be in equilibrium if q is equal to….[KCET 2003]
- If E is electric field strength between the plates, the time period of pendulum is given by...[KCET 2006]
- The final charges on the capacitors are..[KCET 2019]
- As a result the potential difference between the plates…..[KCET 1999]
- The intensity of the electric field at (−2,1,0) is…..[KCET 2007]
Sample Questions
Ques. Why is the electric field within a cavity zero? Specify a single application of electrostatic shielding. (2 marks)
Ans. When a current-carrying conductor is placed in an electric field Ec, the electrons within it acquire mobility in the opposite direction of the electric field. Furthermore, charge redistribution generates its own electric field Ep. As a result, the net electric field, Ec - Ep, becomes zero. As a result, the electric field within the cavity is zero.
Ques. What exactly is electrostatic equilibrium? (1 mark)
Ans. Electrostatic equilibrium is a condition created by charged conductors in which the excess charge distance overcomes the repulsive forces by itself.
Ques. Write one limitation of Faraday's Cage? (2 marks)
Ans. Faraday cages are incapable of blocking both static and slowly changing magnetic fields (as that of the planet Earth). They can, however, shield the interior from external magnetic radiation if the mesh is smaller than the wavelength of the radiation and the shield is sufficiently thick.
Ques. What is the function of a microwave oven as an electrostatic shield? (1 mark)
Ans. The phenomenon used in this example is based on Faraday's cage. To seal electromagnetic energy within itself and shield the exterior from dangerous radiation, microwave ovens use a Faraday cage, which can be seen partially covering the transparent glass.
Ques. What is electrostatic shielding? Give one of its applications. (4 marks)
Ans. Electrostatic shielding is a method of protecting a particular region of space, or any sensitive building/instrument, from the impact of an electric charge's external field. For example, a high-voltage measuring device, such as CRO, is maintained inside a hollow conductor or cage known as the Faraday cage. According to the practical demonstration of electrostatic shielding, the reality of reserving this instrument within the conductor is that when there is no charge present within it, there is an absence of electric charge inside a closed conductor.
Application: It helps in protecting sensitive appliances from external influences such as for T.V. cables.
Ques. State the applications of the Faraday cage. (3 marks)
Ans. Applications are:
- MRI scanning rooms
- Microwave ovens
- They are used in analytical chemistry to decrease noise while performing delicate experiments
Ques. Why do we earth the cage? (2 marks)
Ans. The cage is generally earthed or grounded because if it is not, electrons will disperse in such a way that the interior wall of the cage will acquire an opposite charge to that internal charge. As a result, the outer wall will have the opposite charge as the inside wall.
After the grounding of the cage, the extra charge created around it, drains to the earth, and there is no external field. So this was the situation if we wanted to drop the charge. However if we want to keep something within the cage, it should not be earthed.
Ques. State some of the regular uses of electrostatic shielding. (3 marks)
Ans. Some of the regular uses are:
- Electrostatic shielding in cars since the car has a metallic body it is safe to sit inside an automobile during a lightning storm as it acts as an electrostatic shield.
- Electrostatic shielding is a method used in the cables that carry audio signals in order to protect them from external interference, such as an electric field produced by air electricity or electric sparks.
- Elevators in buildings operate as an electrostatic shield.
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