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Ch. 34 Electric Current

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**Electric Current Movement or “flow” of charge**

Occurs when there is a difference in voltage between the ends of a conductor Electrons carry charges through solid circuits

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**Electric Current (I) Current = charge I = q time t**

Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds.

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**Electric Current (I) Current = charge I = q time t**

Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds. 20 C / 8 s = 2.5 amps

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Voltage Sources Provide a potential difference so that charges are able to flow Examples: Dry Cells or Wet Cells Energy from a chemical reaction is converted to electrical energy

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Voltage (V) The potential energy per coulomb of charge available to electrons moving between terminals Typical voltage in a home is 120 V 120 Joules of energy are supplied to each coulomb of charge that flows in a circuit!!!

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**Charge flows because of an applied voltage across the circuit**

Remember that…. Charge flows because of an applied voltage across the circuit

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**Electric Resistance (R)**

Measured in ohms, Ω Depends on: Conductivity of material Diameter of wire Thick wires have less resistance than thin wires Length of wire Longer wires have more resistance than shorter wires

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**Ohm’s Law I = V/R Current = Voltage / Resistance**

Units: amps = volts / ohms

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I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current?

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I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current? 10 V / 120 ohm = amps

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**Alternating Current (AC)**

Direct Current (DC) Charge always flow in one direction Ex. Batteries Alternating Current (AC) Charge alternates directions as it flows Ex. Our outlets

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**Since our outlets produce AC current, but many appliances use DC, what can we do….. Convert AC to DC**

Diode: a converter that only allows electrons to flow in one direction

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Electric Power The rate at which electrical energy is converted into another form Power = current x voltage P = IV

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Ch. 34 Practice

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Ch. 35 Electric Circuits Series Circuits

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**For Problem Solving in Series**

Resistances are ADDED R1 + R2 + R3 = R total

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**The resistance of one lamp is 10 ohms**

The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

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**The resistance of one lamp is 10 ohms**

The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms

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**The resistance of one lamp is 10 ohms**

The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit?

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**The resistance of one lamp is 10 ohms**

The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 30 ohms I = 0.33 amps

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Parallel Circuits = Rtotal R R R3

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Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

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Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? 1/10 + 1/10 + 1/10 = 1 / Rtotal 0.3 = 1 / Rtotal Rtotal = 1/0.3 = 3.33

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Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit?

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Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 3.33 ohms I = 3 amps

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Ch. 35 Lab and Practice

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