Question

Identify two forms of energy that are involved in each of the following energy conversions relating to a fossil fuel power plant: (a) Burning coal converts water to steam. (b) Steam drives a turbine. (c) A turbine turns a generator. (d) A generator makes electricity.

Short answer

(a) Thermal energy and kinetic energy; (b) Thermal energy and mechanical energy; (c) Mechanical energy and electrical energy; (d) Mechanical energy and electrical energy.

Step-by-step solution

Understanding Energy in Burning Coal

When coal is burned, it undergoes a chemical reaction that releases energy. This energy is primarily in the form of thermal energy (heat). The thermal energy is used to convert water into steam, which involves increasing the kinetic energy of water molecules as they change from liquid to gas.

Identifying Energy in Steam Driving a Turbine

As the steam, carrying thermal energy, is directed onto the blades of a turbine, it transfers its energy, causing the turbine to spin. The spinning of the turbine involves converting the thermal energy of steam into mechanical energy (kinetic energy) of the turbine.

Describing Energy in a Turbine Turning a Generator

The mechanical energy from the spinning turbine is transferred to the generator. This involves the conversion of mechanical energy into electrical energy. The turbine's rotation (mechanical kinetic energy) is used to facilitate electromagnetic induction in the generator to produce electricity.

Explaining Energy in a Generator Making Electricity

Inside the generator, the mechanical energy is converted to electrical energy. This process involves using the kinetic energy from the turbine to move magnetic fields around a set of wires, inducing an electric current (electrical energy) as per Faraday's Law of electromagnetic induction.

Key concepts

Thermal Energy

When coal is burned in a fossil fuel power plant, it releases a large amount of energy in the form of heat, known as thermal energy. This process occurs due to the chemical bonds within the coal breaking down when exposed to oxygen. The heat generated by burning coal is used to convert water into steam. The steam production is crucial as it embodies a shift from potential energy present in water to the thermal energy needed to heat it. In heating water to form steam, the molecules within the water gain kinetic energy and move rapidly, transitioning from a liquid to a gaseous state.

• The conversion of chemical energy in coal to thermal energy during combustion is foundational to the energy production process.
• Thermal energy's primary role is to increase the kinetic activity of water molecules, allowing steam formation.

Understanding thermal energy provides a basis for acknowledging how heat can be harnessed to perform work, such as turning turbines in a power plant.

Mechanical Energy

Mechanical energy comes into play primarily when steam is used to drive a turbine. As steam expands, it generates pressure capable of moving objects – in this case, the turbine blades. Here, what was previously thermal energy contained within the steam is converted to mechanical energy. This form of energy is pivotal as it involves the physical movement or motion of an object, such as a spinning turbine. The transformation from thermal to mechanical energy is a clear demonstration of energy conversion from one form to another. When the steam propels the turbine's blades, it initiates a turning action:

• Mechanical energy is kinetic in nature, involving motion required for electrical energy production.
• The force of the steam must efficiently interact with turbine blades, maintaining strong, uninterrupted motion.

The success of mechanical energy conversion determines the efficiency of power generation, linking directly to the capacity of the plant to produce electricity.

Electrical Energy

Electrical energy is realized at the moment when mechanical energy is transferred from a turbine to a generator. As the turbine rotates, it turns the generator's drive shaft, converting motion into electricity. This process lies at the heart of producing usable electrical energy, which can then be delivered through power lines to homes and businesses. The conversion process capitalizes on mechanical impacts:

• Electrical energy generation depends on electromagnetic induction, a key guideline outlined in Faraday's Law.
• Generators transform kinetic energy from the rotation into electrical currents.

A profound understanding of electrical energy allows appreciation of how seamlessly motion and magnetic forces combine to illuminate and power our daily lives.

Electromagnetic Induction

Electromagnetic induction is the principle that facilitates the conversion of mechanical energy into electrical energy within a generator. It relies on Faraday's Law, which states that a change in the magnetic environment of a loop of wire will cause a voltage or electromotive force (emf) to be induced in the wire. Inside the generator, the mechanical energy from a rotating turbine is leveraged to move magnetic fields past coils of wire:

• Magnetic fields in the generator rotate either through the movement of magnets or wires.
• This movement induces an electrical current by displacing electrons in the wire, efficiently changing mechanical motion into electrical energy.

Electromagnetic induction highlights the sophisticated yet elegant processes allowing modern power generation, transforming kinetic actions into something as easily distributed as electric power.