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Do Now What work is required to move 7 coulombs of charge through a potential difference of 3 volts?

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Electric Current and Circuits!

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Electric Current Electric current: flow of charge Not referring to the speed of the charged particles, but to the quantity of charge that passes a single point in time.

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Electric Current Coulomb Second Ampere (A)

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Example What is the electric current in a conductor if 240 coulombs of charge pass through in 1.0 minute?

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How do we get a current in a conductor? A potential difference is necessary!

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Voltage: the electric potential in a circuit that provides electric pressure to push electrons through the circuit. A voltage source, like a battery or cell, creates a potential difference that moves these electrons. Voltages is measured in _______

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Resistance Electric resistance: the resistance of an object to the flow of electric charge through it Like friction for particles! conversion of energy into heat

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Ohm’s Law R = V I Volts Ampere Ohm (Ω)

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Example When a conductor has a potential difference of 110 volts placed across it, the current through it is 0.50 ampere. What is the resistance of the conductor?

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Resistivity (ρ) Property of a material that affects its resistance resistivity, resistance

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Resistance Resistivity Length of the conductor Cross-sectional area

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Example What is the resistance at 20°C of an aluminum wire that is 0.2 meter long and has a cross sectional area of 1.00 x 10 -3 square meter? (ρ= 2.65 x10 -8 Ωm)

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What do we use to measure the current in a circuit? An ammeter is placed in a circuit to measure the current. It must be in the path of the current, so that nothing flows without going through the ammeter.

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What do we use to measure voltage in a circuit? A voltmeter is placed across a circuit component to measure the voltage. Voltage does not flow; we measure the potential difference across a component to see the push each coulomb of charge feels to move through it.

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The diagram below represents a simple electric circuit. How much charge passes through the resistor in 2.0 seconds? 1)4.0 C3) 8.0 C 2)2.0 C4) 6.0 C

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Example If I have a circuit hooked up to a 6-V power source, and the light bulb has a resistance of 2 Ω, find the value of the current.

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1) If a 12-volt battery is hooked up to a light bulb and 2.5 amperes of current flow, calculate the resistance of the light bulb. 2) How much voltage is required for 0.02 A to flow through a resistor of 250 Ω? 3) How much current will flow through a 100-ohm resistor if it’s drawing from a source of 120 volts?

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In a simple electric circuit, a 110-volt electric heater draws 2.0 amperes of current. The resistance of the heater is 1)220 ohms2) 28 ohms 3) 55 ohms4) 0.018 ohms

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A 9.0-volt battery is connected to a 5.0- ohm resistor as shown below. What is the current through the resistor? 1)9.0 A2) 5.0 A 3) 1.8 A4) 0.55 A

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Practice! Page 616: 2a, 3, 4 Page 627: 32, 33a, 35 Page 628: 40-42

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EXIT QUIZ

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1. The ratio of the potential difference across a conductor to the current in the conductor is called (1) Conductivity (3) charge (2) resistance (4) power

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2. How much current is drawn by a blender with a resistance of 40 Ω that is connected to a potential difference of 150 V?

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3. How long does it take a total charge of 3.0 C to pass through a cross-sectional area of wire that carries a current of 23 A?

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