DP IB Physics: SL
D. Fields
D.4 Induction
DP IB Physics: SLD. FieldsD.4 InductionLinking questions: | |
|---|---|
| a) | How is the efficiency of electricity generation dependent on the source of energy? |
| b) | Faraday’s law of induction includes a rate of change. Which other areas of physics relate to rates of change? (NOS) |
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a) How is the efficiency of electricity generation dependent on the source of energy?
- Solution:
- Depending on the energy source and technology employed, power generating efficiency varies greatly.
- In general, fossil fuels like coal and natural gas have poorer energy conversion efficiency because of heat loss throughout the process, but renewable energy sources like solar, wind, and hydro are thought to be more efficient.
- The type of energy source and the technology used to convert it have a significant impact on the efficiency of electricity generation, or the percentage of the initial energy input that is effectively transformed into usable electrical energy. The definition of efficiency is:
- [math] \text{Efficiency} = \left( \frac{\text{Useful electrical energy output}}{\text{Total energy input}} \right) \times 100\% [/math]
- Thermal power plants (Fossil fuels, Nuclear):
- They work by boiling water with heat (from burning coal, gas, oil, or nuclear fission) to create steam, which rotates a turbine that is connected to a generator.
- The Carnot efficiency limit governs:
- [math] \eta = 1 – \frac{T_{\text{cold}}}{T_{\text{hot}}} [/math]
- – Typical efficiency: 30% – 45%
- ⇒ Renewable Mechanical sources (Hydroelectric, wind, Tidal):
- Directly transform potential or kinetic energy into mechanical energy (turbine rotation) and then electrical energy.
- Eliminating the heat stage results in fewer energy transformations and waste.
| Source | Typical Efficiency |
|---|---|
| Hydroelectric | 85% – 95% |
| Wind | 30% – 45% |
| Tidal | 70% – 80% |
- – More direct conversion = higher efficiency
- – No combustion losses
- Solar (photovoltaic):
- Unlike thermal power plants, solar panels do not naturally lose energy during energy generation, while having a very poor direct energy conversion efficiency (usually 15-20%).
- Wind:
- Modern wind turbines can attain great practical efficiencies, and wind turbines have a high theoretical efficiency limit (Betz’s limit).
- Hydro:
- Known for their high efficiency and dependability, hydroelectric power facilities use the force of flowing water to operate turbines.
- ⇒ Factors affecting Efficiency:
- Heat Rate:
- The quantity of energy needed to produce one kWh of electricity is used by power plants to gauge efficiency. Higher efficiency is indicated by a lower heat rate.
- Technology:
- Efficiency is increased by more recent innovations like as ultra-supercritical advanced coal plants and combined-cycle gas turbines.
- Maintenance and Operation:
- Maintaining and enhancing efficiency in power plants also heavily depends on proper maintenance and efficient operation.
- Figure 1 Various sources of energy can be used to power human activities
b) Faraday’s law of induction includes a rate of change. Which other areas of physics relate to rates of change? (NOS)
- Solution:
- There are other areas of physics that deal with rates of change besides Faraday’s law of induction, which explains the connection between a changing magnetic field and induced voltage.
- Understanding rates of change is also essential to many other branches of physics, including as dynamics, kinematics, and calculus-based physics.
- In particular, Faraday’s law of induction establishes a relationship between the induced electromotive force (EMF) and the rate at which magnetic flux changes.
- Although the concept of a rate of change is central to electromagnetism, it is also essential to many other branches of physics:
- Kinematics:
- This area of mechanics studies how objects move. Key ideas in kinematics include acceleration (the rate at which velocity changes) and velocity (the rate at which position changes).
- Dynamics:
- By taking into account the forces that produce motion, dynamics builds upon kinematics. Force and the rate of change of momentum, or mass times velocity, are closely related by Newton’s second law of motion ([math]F = ma[/math]).
- Calculus-based physics:
- Calculus, which is fundamentally about rates of change, is used to express many physical laws and connections.
- For instance, calculating the derivative of the position function with respect to time yields the instantaneous velocity, which is a calculus concept.
- Likewise, the derivative of the velocity function is the instantaneous acceleration.
- Figure 2 Faraday’s law of induction