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Base your answers to the question on the information below.

Base your answers to the question on the information below. A copper wire at 20°C has a length of 10.0 meters and a cross-sectional area of 1.00 × 10-3 meter2. The wire is stretched, becomes longer and thinner, and returns to 20°C. What effect does this stretching have on the wire’s resistance?

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Base your answers to the question on the information below.

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  1. Base your answers to the question on the information below. A copper wire at 20°C has a length of 10.0 meters and a cross-sectional area of 1.00 × 10-3 meter2. The wire is stretched, becomes longer and thinner, and returns to 20°C. What effect does this stretching have on the wire’s resistance? • Resistance stays the same • Resistance decreases • Resistance is halved • Resistance increases What effect does this stretching have on the wire’s resistivity?

  2. Why Make Electrons Flow Anyway? 4.2.3A Ohm’s Law & Circuit Basics

  3. Ohm’s Law • Voltage results in current flow • More voltage = more current • Resistance opposes current flow • More resistance = less current

  4. Example #1 • A potential difference of 25.0 volts is supplied to a circuit with 100 ohms of resistance. • How much current flows through this circuit? I = V / R I = 25.0 V / 100 Ω I = 0.25 A

  5. Example #2 • A current of 2.0 amperes flows through a 10 ohm resistance. • What voltage must be applied to this resistance? I = V / R V = IR V = (2.0 A)(10 Ω) V = 20 V

  6. Example #3 • A 10 volt battery establishes a current of 5.0 amperes in a circuit. • What is the resistance of this circuit? I = V / R R = V / I R = (10 A) / (5.0 A) R = 2.0 Ω

  7. What is a circuit? • A continuous loop through which current flows from an area of high voltage to a an area of low voltage.

  8. Circuit Elements – Voltage Sources cell battery

  9. Circuit Elements – Resistances fixed resistor variable resistor lamp

  10. Circuit Elements – Switch switch

  11. Circuit Elements – Measuring Devices Measures: VOLTAGE Resistance: HIGH Connect to circuit: OUTSIDE Measures CURRENT Resistance: LOW Connect to circuit: INSIDE voltmeter ammeter

  12. Proper Use of Meters 5 V 2.5 Ω 0 V 2 A 2 A 0 V 5 V 5 V NEXT

  13. End of 4.2.3A

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