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Published byCarol Richards Modified over 4 years ago

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Circuits, Volts, Amps, and Resistance

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Series circuits Simple circuits that have only one path for the current to flow are called series circuits.

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Series circuits can be compared to that of a race track.

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Parallel Circuits Parallel circuits are circuits that allow electricity to flow in multiple paths.

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Parallel circuits are more like city streets than a race track. They give the electricity options for movement.

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The Battery Batteries contain stored electric potential energy from chemical reactions that go on inside the battery. A good example of the reaction is: Zn + Cu 2+ = Zn 2+ + Cu

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The battery provides the potential energy to do “work” In order to do this “work” the battery must be connected in a closed circuit

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Energy is measured in “Joules” The energy that is stored in the battery is also measured in Joules. Potential energy difference is measured in Joules per Coulomb or Volts.

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Therefore: V = E QSo Potential energy difference = the amount of stored energy charge charge

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We can measure potential energy difference using a voltmeter. The measure is in volts. V

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The voltmeter must be put in parallel with the circuit. This means it must create it’s own separate loop in the circuit to work properly.

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The voltmeter will measure the difference at one point on the circuit and compares it to another point on the circuit.

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The Ammeter An ammeter measures current through the circuit. It measures amps Think about current as the speed that the charges travel, an ammeter is like a speed radar gun for electricity. A

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An ammeter must be put in series to work properly.

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Resistance What does it mean to “resist”? What would be harder? 1.Pushing a 50kg box across carpet? 2.Pushing a 50kg box across tile floors?

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Resistance is the property of a substance to hinder motion. A resistor converts electric energy into other forms of energy (heat, light)

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Resistance is the ratio of potential energy difference (voltage) across a load, to the current through the load Resistance = Voltage Current Current Resistance is measured in Ohms or Ω

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Ohm’s Law This equation is referred to as Ohm’s Law Where V = IR V IR

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If we had a voltmeter and a ammeter we could measure the resistance

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Example Question What is the resistance of the heating coil of an electric heater, if a current of 12.5A runs through it, when connected to a wall outlet of 120V? Given:Solution:Paraphrase:

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Example Question What is potential difference (voltage) across a light bulb that has a resistance of 3ohms and a current of 1.5A Given:Solution:Paraphrase:

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Factors that effect resistance 1.Length – resistance increases with length 2.Cross sectional area – resistance decreases when area increases 3.Temperature – resistance increases when temperature decreases 4.Material – some metals allow electrons to move more freely than others

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Page 342 #1-6 1.In your own words explain electrical resistance. 2.What is the formula for resistance and what units are equivalent to the ohm? 3.List 3 characteristics of a wire that affect its resistance. 4.A light bulb passes a current of 0.83 A when the potential difference is 120V. What is the bulb’s resistance? 5.What is the potential difference across an electric water heater element that has a resistance of 32ohms when a current through it is 6.8 A? 6.Matt says that if the resistance of a load becomes larger, the current must become larger as well. Melissa explains that the current should decrease. Who is correct? Explain.

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