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Electricity and Magnetism

Electricity and Magnetism. Chapter 19 Page 378-393. Electricity. Refers to the presence of electric current in wires, motors, light bulbs and other devices. Travels in a circuit, 3 types of natural circuits

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Electricity and Magnetism

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  1. Electricity and Magnetism Chapter 19 Page 378-393

  2. Electricity • Refers to the presence of electric current in wires, motors, light bulbs and other devices. • Travels in a circuit, • 3 types of natural circuits • A. The nerves in your body are an electrical circuit connecting muscles to messages from the brain

  3. B. The tail of an electric eel makes an electric circuit when it stuns a fish with a jolt of electricity. • C. The Earth makes a giant circuit when lightning carries electric current between the clouds and the ground

  4. Circuit Diagrams • When drawing a circuit diagram symbols are used to represent each part of the circuit • Circuit Symbols and Circuit Diagrams

  5. Open and closed circuits • Electric current only flows through a closed circuit. • A closed circuit is a circuit with a complete and unbroken path between the source of the current and the return of the current to the source. • An open circuit is a circuit with a break in it

  6. Short circuit • Is not the same as either an open or closed circuit. A short circuit is usually an accidental extra path for current to flow in. A short circuit is an easy but dangerous shortcut that current can travel through to avoid one or more of the electrical components in the circuit.

  7. Current and Voltage • Current is what actually flows through wires, carries energy and does work. • Voltage measures the difference in energy between two places in a circuit. • Electric current is mesured in amperes or Amps (A)

  8. Conventional current is when the direction of current is from the positive to the negative end of a battery • Current in equals the current out • Voltage is a measure of electric potential energy just like height is a measure of gravitational potential energy

  9. Voltage • Is measured in volts (V) • A voltage difference of 1 volt means 1 amp of current does 1 joule of work in 1 second. • 1 joule per second = watt • Multimeter which can measure voltage or current

  10. Batteries • A battery uses chemical energy to create a voltage difference between its two terminals. • Ammeters are designed specifically to measure only current • Circuit breakers and fuses are two kinds of devices that protect circuits from too much current by creating a break in the circuit and stopping the current.

  11. Electrical Resistance • Resistance is a measure of how easily electric current moves through an object or electrical device. • The more resistance the circuit has the less current that flows through it. • Is measured in ohms • For a given voltage the greater the resistance the less the current

  12. 1 volt causes a current of 1 amp to flow through a resistance of 1 ohm • Use a multimeter to measure the resistance of wires light bulbs and other devices

  13. Ohm’s law • Current is directly proportional to voltage and is inversely proportional to resistance. • I = V/R • I is current • V is voltage • R is resistance

  14. 3 equations of ohm’s law

  15. Resistors • Fixed resistors have a resistance that cannot be changed( usually uses color coding) Variable resistors aka potentiometers can be adjusted to have a range of resistance. Eg dimmer or volume

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