Grade 11
  1. Mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two and three dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration and deceleration  1.1.6. Graphical analysis of motion  1.1.7. Equations of motion (advanced derivations)  1.1.8. Free fall and terminal velocity  1.1.9. Projectile motion  1.1.10. Relative velocity in one and two dimensions  1.1.11. Motion of a car on an inclined plane  1.2. Dynamics  1.2.1. Newton's laws of motion and their applications  1.2.2. Inertia and Newton's first law  1.2.3. Force and types of force  1.2.4. Static and kinetic friction  1.2.5. Circular motion and centripetal acceleration  1.2.6. Non-uniform circular motion  1.2.7. Banking of roads and curves  1.2.8. Momentum and Impulse  1.2.9. Conservation of momentum in one and two dimensions  1.2.10. Applications of Newton's Third Law  1.3. Work, Energy and Power  1.3.1. Work done by a constant and variable force  1.3.2. Work–energy theorem  1.3.3. Kinetic and potential energy  1.3.4. Gravitational and elastic potential energy  1.3.5. Conservation of mechanical energy  1.3.6. Power and instantaneous power  1.3.7. Efficiency of machines  1.3.8. Work done by conservative and non-conservative forces  1.4. Rotational motion  1.4.1. Torque and angular acceleration  1.4.2. Rotational equilibrium  1.4.3. Moment of inertia and its applications  1.4.4. Angular momentum and its conservation  1.4.5. Kinetic energy of rolling motion and rotation  1.4.6. Parallel and Perpendicular Axis Theorem  1.4.7. Dynamics of rotational motion
  2. Gravitational force  2.1. Universal gravitation  2.1.1. Newton's law of universal gravitation  2.1.2. Gravitational field and potential  2.1.3. Change in acceleration due to gravity  2.1.4. Kepler's laws of planetary motion  2.1.5. Orbital mechanics and satellites  2.1.6. Escape velocity and orbital velocity  2.1.7. Weightlessness and free fall  2.1.8. Gravitational potential energy and energy in orbits  2.1.9. Black holes and gravitational lensing
  3. Properties of matter  3.1. Fluid mechanics  3.1.1. Density and pressure in liquids  3.1.2. Pascal's theory and applications  3.1.3. Archimedes' Principle and Buoyancy  3.1.4. Bernoulli's equation and applications  3.1.5. Continuity equation and the Venturi effect  3.1.6. Surface tension and capillarity  3.1.7. Viscosity and Poiseuille's Law  3.1.8. Reynolds number and turbulence  3.2. Elasticity and deformation  3.2.1. Hooke's law and the stress-strain relation  3.2.2. Elastic modulus and applications  3.2.3. Deformation and yield strength of solids
  4. Thermal physics  4.1. Heat and temperature  4.1.1. Thermometric properties and temperature scale  4.1.2. Thermal expansion of solids, liquids and gases  4.1.3. Heat transfer system  4.1.4. Specific heat capacity and calorimetry  4.1.5. Latent heat and phase change  4.2. Kinetic theory of gases  4.2.1. Molecular model of gases  4.2.2. Kinetic explanation of temperature  4.2.3. Ideal Gas Equation and Deviations  4.2.4. Mean free path and Maxwell–Boltzmann distribution  4.3. Laws of Thermodynamics  4.3.1. Zeroth Law and Thermal Equilibrium  4.3.2. First Law and Internal Energy  4.3.3. The Second Law and Entropy  4.3.4. Carnot cycle and heat engines  4.3.5. Refrigerators and heat pumps
  5. Waves and oscillations  5.1. Simple Harmonic Motion  5.1.1. Equations of SHM  5.1.2. Energy in SHM  5.1.3. Damped and forced oscillations  5.1.4. Resonance and applications  5.1.5. Pendulum and spring-mass system  5.2. Wave motion  5.2.1. Types of mechanical waves  5.2.2. Wave motion and energy transport  5.2.3. Superposition Principle and Standing Waves  5.2.4. Reflection, Refraction and Diffraction  5.2.5. Doppler effect in sound and light  5.2.6. Pulsations and interference
  6. Electricity and Magnetism  6.1. Electrostatics  6.1.1. Electric charge and conservation  6.1.2. Coulomb's law and its applications  6.1.3. Electric field and electric flux  6.1.4. Electric potential and potential energy  6.1.5. Capacitance and Energy Stored in a Capacitor  6.2. Current Electricity  6.2.1. Ohm's law and electrical resistance  6.2.2. Resistivity and temperature dependence  6.2.3. Kirchhoff's Laws and Circuit Analysis  6.2.4. Electrical power and efficiency  6.2.5. Combination of resistors  6.3. Magnetism and Electromagnetism  6.3.1. Magnetic fields and their sources  6.3.2. Magnetic force on moving charges  6.3.3. Electromagnetic induction  6.3.4. Faraday's and Lenz's laws  6.3.5. Inductance and Transformer  6.3.6. Alternating current and its applications
  7. Optics  7.1. Reflection and Refraction  7.1.1. laws of reflection and refraction  7.1.2. Mirrors and lenses  7.1.3. Total internal reflection and optical fiber  7.2. Wave optics  7.2.1. Interference and Diffraction  7.2.2. Young's double-slit experiment  7.2.3. Polarization of light
  8. Modern Physics  8.1.1. Photoelectric effect and Einstein's theory  8.1.2. Wave–particle duality  8.1.3. Heisenberg's uncertainty principle  8.1.4. Compton Effect  8.2. Atomic and Nuclear Physics  8.2.1. Atomic model and energy levels  8.2.2. Radioactive decay and half-life  8.2.3. Nuclear Fission and Fusion
  9. Electronics and Communication  9.1. Semiconductors  9.1.1. pn junction and diode  9.1.2. Transistors and Logic Gates  9.1.3. Integrated Circuits and Applications  9.2. Communication Systems  9.2.1. Basics of Analog and Digital Communication  9.2.2. Wireless and Optical Communication  9.2.3. Modulation and Demodulation

Grade 11 → Electricity and Magnetism → Current Electricity ↓


Electrical power and efficiency


In the field of current electricity, the concepts of electrical power and efficiency are fundamental. They help us understand how electrical circuits work and how energy is transferred from one form to another. This subject is essential in the study of physics because it connects to many real-world applications, from household appliances to industrial machines.

Introduction to electric power

Electric power can be defined as the rate of transfer of electrical energy through an electric circuit. The unit of electric power is the watt (W), which is equal to one joule per second. In symbols, power is represented as P

The formula for electric power is given as:

P = V * I

Where:

  • P is the power in watts (W).
  • V is the voltage across the device in volts (V).
  • I The current flowing through the appliance is in amperes (A).

Understanding voltage, current and their relation to electricity

In a simple electric circuit, let us consider a battery connected to a bulb. The battery provides a potential difference (voltage), which causes current to flow through the bulb, lighting it up. Voltage represents the energy per unit charge provided to the circuit. Current is the flow of electric charge.

If a light bulb is marked "60W, 120V," it means the bulb uses 60 watts of power when connected to a 120 volt source.

Calculation of power

Let's use the formula to find how much current is flowing into the bulb:

I = P / V

For the bulb,

I = 60 W / 120 V = 0.5 A

Therefore a current of 0.5 ampere flows in the bulb.

Alternative energy sources

Using Ohm's law, V = I * R, where R is the resistance in ohms, we can obtain another expression for power.

Power in terms of current and resistance

Substituting V I * R into the power formula:

P = I^2 * R

This formula tells us how power is directly related to current and the square of the resistance.

Power in terms of voltage and resistance

Similarly, substituting I for V / R gives:

P = V^2 / R

It represents power in terms of voltage and resistance. Both of these alternative formulas are useful in different contexts.

Visual example

Battery V Bulb

Electrical efficiency

Electrical efficiency refers to how well a system converts electrical energy into another energy form. It is essentially the ratio of useful output energy to the total input energy, often expressed as a percentage.

The formula for efficiency is:

Efficiency (%) = (Useful Power Output / Total Power Input) * 100

In practice, some energy is always lost in the conversion process (usually as heat). Higher efficiency means that less energy is wasted.

Example of efficiency calculation

Consider a motor that consumes 1000 W of power and delivers 700 W of mechanical power.

Efficiency = (700 W / 1000 W) * 100 = 70%

This means that the motor operates at 70% efficiency, and 30% of the electrical energy is converted into heat or other forms of energy.

Improve efficiency

There are many ways to improve the efficiency of electrical equipment, such as:

  • Using better materials with higher conductivity.
  • Improving the design of equipment to reduce energy waste.
  • Regular maintenance to ensure optimum performance.

Proficiency in various tools

The efficiency of different electrical appliances varies:

  • LED lights are more efficient than incandescent bulbs, because they convert more energy into light rather than heat.
  • Energy-efficient appliances such as refrigerators and air conditioners consume less power for the same functions than older models.

Visualization of efficiency

Input 1000W Production 700W Efficiency: 70%

Motors and lighting are examples of practical applications of electrical power and efficiency. Understanding these concepts is important for developing and using technologies that minimize wastage while maximizing energy use.


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Electrical power and efficiency

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