Electricity and Power Calculations

Current Electricity

• Electric current is the flow of electricity in a circuit.

Electrical Power and Efficiency

• Electrical power is when energy is transferred in an electrical circuit.
• 1 watt is the same as 1 Joule.
• 1 watt = 1000 kilowatt-hours (KW/hr)
• Efficiency is the energy output compared to the energy input of an object.
• Electrical power is the rate of electrical energy produced or consumed in a given time.

Efficiency Formula

• Percent Efficiency = (Energy Output / Energy Input) x 100

Example Calculation

• What is the percent efficiency of a laptop that used 3500 J but produces 750 J?
  • Given: Energy Output (Eout) = 750 J
  • Given: Energy Input (Ein) = 3500 J
  • Calculation: % Efficiency = (750 J / 3500 J) x 100 = 21.43%

Generating Current Electricity

• To generate electricity, a turbine generator transforms mechanical energy into electrical energy.
• Common energy sources for generators include natural gas, coal, nuclear fission, biomass, petroleum, geothermal, and solar thermal.
• Heat produced from these sources creates steam, which moves the turbine blades.

Current and Voltage

• Voltage is the measure of electric potential energy per unit charge.
• Current is the flow of electric charge through a circuit.
• Voltage is measured in volts.
• Current is measured in amperes.

Resistance

• Resistance is a material's ability to oppose the flow of electric current.
• Higher resistance leads to lower current and higher temperature in the material.
• Resistance is measured in ohms (Ω).

Electric Circuit

• An electric circuit is a continuous path allowing electron flow.
• Components in a circuit are connected by conducting wires.
• A circuit needs a source of electrical energy to function.

Electric Cell (Component)

• Electric cells/batteries have positive and negative terminals.
• Electrical devices convert electrical energy into another form of energy.

Conducting Wire

• Conducts electricity, often made of copper with a protective plastic coating.

Switch

• Controls the flow of electricity in a circuit.

Unit of Measurement (Watt)

• 1 watt (W) = 1 joule/second (J/s)
• Higher wattage indicates more electrical energy a device uses or produces.

Renewable and Nonrenewable Resources

• Renewable resources replenish at the rate they are used (e.g., timber, wind, solar).
• Nonrenewable resources have a limited supply (e.g., coal, natural gas).