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 → Current Electricity ↓


Series and Parallel Circuits


Electricity is a fundamental part of our daily lives. It powers our homes, our electronic devices, and even some of our cars. It is important to understand the basic concepts of electricity and its circuits. In this lesson, we will explore the concepts of series and parallel circuits, which are important in the fields of electrical engineering and physics.

What is an electrical circuit?

An electrical circuit is a closed path through which electric current flows. It typically includes an energy source such as a battery, conductors such as wires, and various electrical components such as resistors, switches, and lamps.

Series Circuit

In a series circuit, components are connected one after the other in such a way that the same current flows through each component.

Features of series circuit

  • The total resistance of the circuit is the sum of the individual resistances:
    R total = R 1 + R 2 + R 3 + ...
  • Equal current flows through each component.
  • The total voltage in a circuit is the sum of the voltages across each component:
    V total = V 1 + V 2 + V 3 + ...
     Battery
      ,
      ,    
     [R1]---[R2]---[R3]  
      ,    
    ,

Consider three resistors connected in series as shown above. The total resistance is the sum of all three resistors.

Example of a series circuit

Suppose you have three resistors with resistances of 2 ohms, 3 ohms, and 5 ohms connected in series to a 12 volt battery. To calculate the total resistance and current, consider:

R total = 2 + 3 + 5 = 10 ohms

Now, using Ohm's law (V = IR), we find the current:

I = V / R = 12 volts / 10 ohms = 1.2 A

Application

Series circuits are often used in applications where the operation of the circuit does not depend on any one component. For example, in some old-fashioned Christmas lights, if one bulb goes out, the entire string goes out, because they were wired in series.

Parallel circuit

In a parallel circuit, components are connected at two identical points, creating multiple paths for electric current.

Features of parallel circuit

  • The voltage across each component is the same.
  • The total current flowing in the circuit is the sum of the currents passing through each path:
    I total = I 1 + I 2 + I 3 + ...
  • The total resistance in the circuit is less than the smallest individual resistance. It can be calculated as:
    1/R total = 1/R 1 + 1/R 2 + 1/R 3 + ...
     Battery
      ,
      ,
     [R1] [R2]
      ,
     ----[R3]----

In the above parallel circuit, the voltage across each resistor is the same. The total current is divided into parallel branches.

Example of a parallel circuit

Imagine you have three resistors of 6 ohms, 2 ohms and 3 ohms connected in parallel across a 9 volt battery. The total resistance can be calculated as:

1/R total = 1/6 + 1/2 + 1/3

Simplifying this, you get:

1/R total = 1/6 + 3/6 + 2/6 = 6/6

Therefore, R total = 1 ohm

Total current supplied by the battery: I = V / R = 9 volts / 1 ohm = 9 A

Application

Parallel circuits are commonly used in home wiring systems. Each device in the home, such as a light bulb or power outlet, functions independently. If one stops working, the others continue to work.

Comparison of series and parallel circuits

Features Series Circuit Parallel Circuit
Resistance Additive Reciprocal sum
Current Same through all components Division between paths
Voltage Breaks down into components Same in all components
Failure If even one fails the circuit is broken Other components continue to function

Formula recap

Series circuit formula

  • Total resistance: R total = R 1 + R 2 + R 3 + ...
  • Current: I = V / R total

Parallel circuit formula

  • Total resistance: 1/R total = 1/R 1 + 1/R 2 + 1/R 3 + ...
  • Current: I = V / R total

Conclusion

Understanding the difference between series and parallel circuits allows students and hobbyists to design circuits that meet their specific needs. Series circuits are useful for simple applications where equal current supply is required, while parallel circuits provide stability and flexibility for complex systems.

Test your understanding

Consider this scenario: You have a circuit consisting of a 10 ohm resistor and a 20 ohm resistor connected in series, powered by a 30-volt battery. Calculate the total resistance, the total voltage, and the total current.

Then imagine that these two resistors are connected in parallel to the same 30-volt battery. How does the calculation change? By solving these problems, you can strengthen your understanding of series and parallel circuits.


Grade 9 → 6.2.4


U
username
0%
completed in Grade 9

← Prev (6.2.3)
Factors affecting resistance
Next (6.2.5) →
Heating effect of electric current

Comments 



Series and Parallel Circuits

https://www.physicsflow.com/g9/6.2.4?pfal=en