Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Electricity and Magnetism → Current Electricity ↓


Electric power and energy


Electricity is an essential part of our daily lives. It allows us to light our homes, run our appliances, and do many other things. But to use electricity effectively, we need to understand what electrical power and energy are.

Understanding electric current

Before learning about electric power and energy, it is important to understand electric current. Electric current is the flow of electric charge. We can think of it as water flowing through a pipe. The more electric charge flowing, the larger the current.

What is electric power?

Electric power is the rate at which electrical energy is transferred through an electrical circuit. It tells us how quickly energy is being used or produced. The unit of power is watt (W). Power is calculated using the formula:

Power (P) = Voltage (V) × Current (I)

In this formula:

  • Voltage (V) is the potential difference between two points in a circuit. Its unit is volt.
  • Electric current (I) is the flow of electric charge. Its unit is ampere or amp.

Example of power calculation

Suppose you have a light bulb that operates on a voltage of 120 volts and a current of 0.5 amperes. To find the power used by this bulb, you would use the formula:

Power = Voltage × Current 
Power = 120 V × 0.5 A = 60 W

This means that the light bulb uses 60 watts of electricity.

Understanding electrical energy

Electrical energy is energy provided by the flow of electric charge through a conductor. The unit of energy is the joule (J), but when talking about electrical energy it is usually expressed in kilowatt-hours (kWh).

Electrical energy is calculated using this formula:

Energy (E) = Power (P) × Time (t)

In this formula:

  • Power (P) is the rate of energy use. Its unit is watt.
  • Time (t) is the period for which the energy is used. The unit is seconds or hours.

Example of energy calculation

Let's say an appliance uses 200 watts of power and runs for 3 hours. To find the energy used by this appliance, you would use the formula:

Energy = Power × Time 
Energy = 200 W × 3 h = 600 Wh

To convert watt-hours to kilowatt-hours, divide by 1000:

600 Wh = 0.6 kWh

This means that this appliance uses 0.6 kilowatt-hours of energy.

Visualization of electric power and energy

Let's visualize how power affects energy consumption. Imagine water flowing out of a tank:

Water Tank

This tank represents the source of power, and the water flowing out represents the use of energy. The faster the water flows (more power), the more water (energy) is used in a given time.

Relation between power, energy and time

Power, energy and time are directly related. If power or time increases, energy usage increases. We can understand this with an example:

  • If a bulb with a 60 W power rating runs for 2 hours, it uses 120 Wh of energy.
  • If the same bulb runs for 4 hours then 240 Wh of energy is used.
  • If a 100 W bulb runs for 2 hours it uses 200 Wh of energy.

This shows how both power and time affect the energy consumed.

Application of electric power and energy

Electrical appliances are rated based on their power consumption. This rating is needed to determine how much energy they will use:

  • A refrigerator consumes 150 watts, meaning it consumes 0.15 kWh every hour.
  • An electric heater may use 1000 watts, and consumes 1 kilowatt hour per hour.

Understanding these ratings helps in estimating electricity bills, which are often based on energy consumption in kilowatt-hours.

Economic and environmental implications

The amount of energy we use has an impact on both our cost and the environment. More electricity use means higher electricity bills. In addition, using energy efficiently helps reduce our environmental impact. For example:

  • Choosing energy-efficient appliances can reduce electricity use.
  • Turning off appliances when not in use saves energy and reduces costs.
  • Environmental impacts can be reduced by using renewable energy sources such as solar power.

Security considerations

Understanding electricity and energy is important for safety. Overloading a circuit can cause overheating, which can cause a fire. Calculating the power and energy needs of appliances ensures that circuits are not overloaded.

For example, let's say a circuit can handle up to 15A at 120V. To ensure safety, calculate the maximum power it can handle:

Power = Voltage × Current 
Maximum power = 120 V × 15 A = 1800 W

Keeping power consumption below this level helps prevent hazards.

Conclusion

Electric power and energy are fundamental concepts in understanding how electricity works in our homes and buildings. They explain how we use and pay for our energy, and they help ensure that we use electricity safely and efficiently.

By knowing how electricity and energy interact, we can make smart decisions about the appliances we use and how we use them, leading to economic savings and a positive impact on the environment.


Grade 10 → 5.2.5


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Electric power and energy

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