Grade 9
  1. Mechanics  1.1. Motion  1.1.1. Types of motion  1.1.2. Distance and displacement  1.1.3. Speed and Velocity  1.1.4. Acceleration  1.1.5. Graphical representation of motion  1.1.6. Equations of motion  1.1.7. Uniform and non-uniform motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Relative speed  1.1.10. Circular motion  1.2. Laws of force and motion  1.2.1. The concept of force  1.2.2. newton's first law of motion  1.2.3. Newton's second law of motion  1.2.4. Newton's third law of motion  1.2.5. Inertia and types of inertia  1.2.6. Motion  1.2.7. Conservation of momentum  1.2.8. Application of Newton's laws in daily life  1.2.9. Types of Forces (Contact and Non-Contact)  1.2.10. Friction and its effects  1.3. Gravitational force  1.3.1. Newton's law of universal gravitation  1.3.2. Importance of Gravitational Force  1.3.3. Acceleration due to gravity  1.3.4. Free fall and weightlessness  1.3.5. Mass and weight  1.3.6. Variation of g with height and depth  1.3.7. Kepler's laws of planetary motion  1.3.8. Satellites and their orbits  1.4. Work, Energy and Power  1.4.1. Concept of work  1.4.2. Positive and negative actions  1.4.3. Work done by constant and variable force  1.4.4. Energy and its forms  1.4.5. Kinetic energy and potential energy  1.4.6. Law of conservation of energy  1.4.8. Commercial unit of energy  1.4.9. Work–energy theorem  1.5. Simple machines  1.5.1. Types of simple machines  1.5.2. Mechanical advantage  1.5.3. Machine efficiency  1.5.4. Levers and their types  1.5.5. Pulleys and Inclined Planes  1.5.6. Gears and their uses
  2. Properties of matter  2.1. States of matter  2.1.1. Solids, liquids and gases  2.1.2. Properties of different states of matter  2.1.3. Change in state of matter  2.1.4. Plasma and Bose–Einstein condensate  2.2. Density and pressure  2.2.1. Concept of density and relative density  2.2.2. Pressure in solids, liquids and gases  2.2.3. Pascal's law and its applications  2.2.4. Atmospheric pressure and its variations  2.2.5. Surface tension and capillarity  2.3. Buoyancy and Archimedes' principle  2.3.1. Buoyant force  2.3.2. Archimedes principle  2.3.3. Applications of Archimedes' Principle  2.3.4. floating and sinking objects  2.3.5. Theory of Flotation and Archimedes' Principle
  3. Heat and Thermodynamics  3.1. Temperature and heat  3.1.1. Concept of heat and temperature  3.1.2. Temperature measurement  3.1.3. Temperature scales  3.2. Heat transfer  3.2.1. Conduction of heat  3.2.2. Convection of heat  3.2.3. heat radiation  3.2.4. Applications of heat transfer  3.2.5. Thermal conductivity  3.3. Thermal expansion  3.3.1. Expansion of solids, liquids and gases  3.3.2. Abnormal expansion of water  3.3.3. Applications of Thermal Expansion  3.4. Specific heat capacity and latent heat  3.4.1. Concept of specific heat capacity  3.4.2. Measurement and applications of specific heat  3.4.3. Latent heat of fusion and vaporization  3.4.4. Heat Engines and Efficiency
  4. Waves and sound  4.1. Waves and their types  4.1.1. Mechanical and electromagnetic waves  4.1.2. Longitudinal and Transverse Waves  4.1.3. Properties of Waves  4.1.4. Wavelength, frequency and speed of the wave  4.1.5. Superimposition of waves  4.2. Sound waves  4.2.1. Nature and transmission of sound  4.2.2. Speed of sound in different mediums  4.2.3. Reflection of sound and echo  4.2.4. Sonar and ultrasound  4.2.5. Resonance and pulsation  4.3. Sound characteristics  4.3.1. Intensity, loudness and quality of sound  4.3.2. Doppler effect in sound
  5. Lighting and Optics  5.1. Reflection of light  5.1.1. Laws of reflection  5.1.2. Reflection from a plane mirror  5.1.3. Reflection from a spherical mirror  5.1.4. Image formation by concave and convex mirrors  5.1.5. Applications of Reflection  5.2. Refraction of light  5.2.1. Laws of refraction  5.2.2. Refractive index  5.2.3. Refraction through a glass slab  5.2.4. Refraction in water and air  5.2.5. Lenses and their types  5.2.6. Image formation by convex and concave lenses  5.2.7. Total internal reflection and its applications  5.3. Dispersion and scattering of light  5.3.1. Spectrum of white light  5.3.2. Prisms and Dispersion  5.3.3. Tyndall effect and blue sky
  6. Electricity and Magnetism  6.1. Electric charge and static electricity  6.1.1. The concept of electric charge  6.1.2. Charging by friction, contact and induction  6.1.3. Electroscope and its working  6.2. Current Electricity  6.2.1. The concept of electric current  6.2.2. Ohm's Law and Resistance  6.2.3. Factors affecting resistance  6.2.4. Series and Parallel Circuits  6.2.5. Heating effect of electric current  6.2.6. Electric power and energy  6.3. Magnetism  6.3.1. Natural and artificial magnets  6.3.2. Properties of magnets  6.3.3. Earth's magnetism  6.3.4. Magnetic field and field lines  6.3.5. Electromagnets and their applications
  7. Modern Physics  7.1. structure of the atom  7.1.1. Atomic Structure and Subatomic Particles  7.1.2. Electrons, Protons, and Neutrons  7.1.3. Rutherford and Bohr model  7.2. Radioactivity  7.2.1. Types of radioactive emissions  7.2.2. Half-life and radioactive decay  7.2.3. Uses and Hazards of Radioactivity
  8. Space science and astronomy  8.1. The universe and its components  8.1.1. Stars and galaxies  8.1.2. Planets and Solar System  8.2. Satellites  8.2.1. Natural and artificial satellites  8.2.2. Use of satellites

Grade 9 → Electricity and Magnetism → Electric charge and static electricity ↓


Electroscope and its working


The electroscope is a simple instrument used to detect the presence of electric charges. It can determine whether an object is positively or negatively charged. This instrument is important in the study of electricity and magnetism, especially when learning about electric charges and static electricity.

What is an electroscope?

The electroscope is an instrument that provides a visual indication of the presence and magnitude of an electric charge. It was first invented by William Gilbert in the early 1600s. The instrument usually consists of a metal rod attached to two thin gold leaves (or other light metal leaves), which are sealed in a glass container to protect them from air flow.

Parts of an electroscope

  • Metal rod: This rod is usually vertical and allows the transmission of electrical charge from the outside to the inside of the leaves.
  • Metal strips: Often made of gold or aluminum because these metals are very thin and can therefore move easily. When charged, the strips move apart.
  • Metal disc or knob: This is the place where the unknown charge is brought near or contacted in order to transfer some charge to the electroscope.
  • Insulating container: A glass container or case ensures that no air flow affects the movement of the leaves and only the actions of electrical charges affect them.

Working principle of electroscope

The working of an electroscope is based on the mutual electrostatic repulsion between like charges. When a charged object is brought near the metal disc, some of its charge is transferred to the rod and reaches the leaves through the metal conductor rod. The leaves acquire the same kind of charge and repel each other, causing them to separate.

Detailed steps of electroscope operation

  1. Charging by contact:

    Suppose you have a charged rod (positively or negatively charged). You touch this rod to the metal disc of the electroscope. As soon as you touch the electroscope, some charge is transferred to it.

    For example, if you have a negatively charged rod, the transfer of charges will cause the electrons to move from the electroscope to the rod.

  2. Movement of leaves:

    Once the electroscope is charged, the metal blades in the container will also have the same charge. Since like charges repel each other, the blades will repel each other and move apart.

  3. Overview:

    The distance between the leaves will depend on the amount of charge. The greater the charge, the greater the repulsion, and the farther apart they will move.

  4. Discharging the electroscope:

    This can be done simply by touching the metal disc with your hand. Your body provides a path for the charges to travel to ground (grounding), thereby neutralizing the electroscope.

Types of electroscopes

Although the basic function remains the same, electroscopes can vary in design and sensitivity. Here are two common types:

1. Pith-ball electroscope

This type uses a small ball of pith – a light and insulating material. This ball is suspended from a stand using a silk thread. When a charged object is brought near the pith ball, the ball moves towards or away from the object depending on the charge. Pith-ball electroscopes are simpler but less sensitive than leaf electroscopes.

2. Gold-leaf electroscope

As explained earlier, the gold-leaf electroscope uses two parallel gold leaves suspended from a rod. It is more sensitive than the pith-ball electroscope and can detect even smaller charges.

Applications of electroscope

  • Charge detection: It can detect whether an object is charged or not.
  • Determining the type of charge: Using a known charged object, you can determine the type of charge on an unknown object.
  • Testing the electric field intensity.

Visualization of electroscope operation

Let's create a simple visual example to understand how leaves diverge. We will use scalable vector graphics (SVG) to depict the structure of a simple leaf electroscope.

This diagram shows the structure of a gold leaf electroscope. The bottom two lines, which look like a "V", are the gold leaves. They come out of the main metal rod that connects to the golden disk.

How to do experiments with an electroscope

Experiments using an electroscope provide a practical understanding of how static electricity and charge work. Here's a simple experiment you can perform:

Experiment: Detection and determination of charge

Required materials:

  • An electroscope
  • A rod made of glass
  • Woolen cloth
  • A plastic rod
  • Silk fabric

Phase:

  1. First make sure that the electroscope is not charged. If it is charged, discharge it by touching its metal disc with your hand.
  2. Charge the glass rod by rubbing it with a woolen cloth. Now bring it near the metal disc of the electroscope without touching it.
  3. Note that the leaves move apart. This indicates the presence of charge. Remove the glass rod and observe the leaves return to their initial uncharged state.
  4. Repeat the process by charging the plastic rod using the silk cloth. Bring it close to the disc of the electroscope.
  5. Observe the movement of the leaves. If they move farther than when you use the glass rod, hypothesize a difference in the amount or type of charge.

Conclusion:

By observing the behavior and deflection of the leaves, you can infer not only the presence but also some properties of the charge, such as its type compared to a known source.

Conclusion

Electroscopes play a vital role in understanding the basic principles of electrostatics and help provide practical information about how charged particles interact. This experiment not only demonstrates the understanding of static electricity but also helps hone important observational and experimental skills in physics.


Grade 9 → 6.1.3


U
username
0%
completed in Grade 9

← Prev (6.1.2)
Charging by friction, contact and induction
Next (6.2) →
Current Electricity

Comments 



Electroscope and its working

https://www.physicsflow.com/g9/6.1.3?pfal=en