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Electric current and electrical energy

Electric current and electrical energy. Electrical energy is the energy of electric charges . Electric current ( I ) is the rate at which charges pass a given point . It is measured in amperes (A) . Electric charges flow from an area of high voltage to an area of low voltage.

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Electric current and electrical energy

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  1. Electric current and electrical energy

  2. Electrical energy is the energy of electric charges. Electric current (I) is the rate at which charges pass a given point. It is measured in amperes (A). Electric charges flow from an area of high voltage to an area of low voltage. The higher the current, the greater the number of charges that pass a point each second.

  3. How do charges move in the current? When there is an electric field in a wire, free electrons will move. The energy of each electron is transferred instantly to the next electron.

  4. Electric current Alternating Current Direct Current

  5. Voltage (V) Is the potential difference between two points in a circuit. Its unit is Volt (v). It is a measure of how much work is needed to move a charge between two points. It is the amount of energy released as a charge moves between two points in the path of a current. The higher the voltage, the more energy is released per charge, and so, the greater the current is.

  6. Resistance (R): Is the opposition to the flow of electric current by a material or device. It is expressed in ohms (Ω). So, it is a type of electrical friction. The higher the resistance is, the lower the current in the material. Resistance depends on four factors: • Material • Thickness • Length • Temperature

  7. 1. Material and Resistance Good conductors Low resistance * Used to make wires Poor conductors High resistance

  8. 2. Resistance, Thickness and Length Thickness increases Low resistance Shorter length Low resistance

  9. 3. Resistance and temperature Temperature increases High resistance, because the atoms move faster at high temperatures Cooling a material to very low temperature Resistance drops to 0 Ω Superconductors

  10. Group Activity: Modeling Resistance Create a model or a poster that illustrates one of the factors that affects resistance Then make a short presentation about it

  11. Generating electrical energy Energy cannot be created or destroyed. It can only be changed into other kinds of energy. Generators convert mechanical energy into electrical energy. Cell is a device that changes chemical or radiant energy into electrical energy and so, produces electricity.

  12. Parts of a Cell: • Electrolyte:A liquid that allows charges to flow. • Pair of electrodes: made of conducting materials (Enter or exit of charges). • Do we use electrolytes in our bodies? How? • Chemical energy Electrical energy

  13. Kinds of Cells: • A. Dry cells: electrolytes are solid or pastelike. • Example is battery in flashlights. • B. Wet cells:electrolytes are liquid. • Example is car battery.

  14. Thermocouple It is a device that converts thermal energy into electrical energy. The greater the temperature difference, the greater the current is.

  15. Photocell is a device that converts light energy into electrical energy. They contain silicon atoms.

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