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Chapter 34

Chapter 34. Electric Current. The Big Idea. Electric current is related to the voltage that produces it and the resistance that opposes it. Ohm’s Law. Voltage equals the current times the resistance. Basic Facts. We use the letter I to represent current.

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Chapter 34

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  1. Chapter 34 Electric Current

  2. The Big Idea Electric current is related to thevoltage that produces it and the resistance that opposes it. Ohm’s Law Voltage equals the current times the resistance

  3. Basic Facts • We use the letterI to represent current. • Current is measured in Amperes. • Ampere or Amps or the Letter A. • We use the letter R to represent resistance. • Resistance is measured in Ohms. • Ohms or the Greek letter omega .

  4. Some Examples with • A Battery with 10Volts is hooked up in a circuit with a resistor at 100. Calculate the current that flows through the circuit. • You want 1 A to flow through a resistor of 1,000. What Voltage battery will you need? 3. You have a battery with 20V. You have 3 different resistors, 10 , 100 , 1000 . Which resistor will give the largest current? Which will give the smallest current?

  5. Power! • To calculate the power used in a circuit is very similar to Ohm’s Law. • Units for power are Watts (W).

  6. Circuit • A Complete Path

  7. We hook the battery up and make a circuit. + _

  8. How to Draw a Battery

  9. Resistors • Resists the flow of electrons. • They get warm when they do this. • Ex. A Light bulb.

  10. Series and Parallel • Series • More then one component in a row • Parallel • One component, multiple paths.

  11. Equivalent Resistance forSeries & Parallel Series Parallel

  12. Remember Charge. • Battery has a positive (+) and a negative (-) side. • The plus (+) side does not have enoughelectrons. • The minus (-) side has too many electrons. • This difference is called a difference in electric potential or more commonly a Voltage.

  13. Why Electrons Move Electric current is the flow of electrons. Remember: Opposites attract. 1. Negative Charges want to move towards positive charges. 2. Electrons move freely through conductors. 3. If there are too many electrons in a place and they have a path to where there aren’t as many electrons, they will move towards that place.

  14. AC/DC • Direct Current (DC) Vs. Alternating Current (AC) Direct current stays the same while alternating current alternates with a given frequency.

  15. Capacitors • Another component of electric circuit is a capacitor. • Commonly called a cap. • They store charge and can be deadly! • The units for caps are called Farad (F).

  16. A capacitor is just two conductors separated by an insulator. Old Style Cap. Modern capacitors

  17. Transistors • Transistors are used in circuits in two ways. • 1. As an amplifier. • Transistors can amplify signals. • 2. As a switch. Transistors can act just like your light switch. • On, current flows, • Off, current does not flow.

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