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Electrical Current Mr. Fleming

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**Expected Performances**

D4. Explain the relationship among voltage, current and resistance in a simple series circuit.

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Essential Question What are the factors that affect how electrons move along a wire?

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**Two types of electricity**

Static electricity: electricity involving a build-up of stationary charges. Current electricity: electricity involving the flow of e- through a material.

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Ohm’s Law Voltage, current and resistance are all related to each other by a formula called Ohm’s Law, developed by George Simon Ohm in 1827. Current = Volts/ Resistance I= V/R

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**Current Current: rate at which electrons move past a point in a wire.**

Measured by using amperes or amps (A)

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Voltage Voltage: the difference in electrical potential between two points. Measured by using Volts (V) Voltage provides the force or push that moves electrons through a wire. An increase in voltage causes an increase in electron flow.

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Resistance Resistance - opposition of a substance to a flow of electrons. Measured by using Ohms (Ω) The higher the resistance; the lower the current.

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**Factors Affecting Resistance**

Material Thickness of a wire Length of a wire Temperature

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Power Equation Power is a function of Voltage and current expressed by the equation. P = I x V

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Power Power: The rate at which energy is transferred or used in an electrical circuit. Measured by using Watts (W)

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**Steps to solving Word Problems:**

Read the problem 2. List all known values with their units 3. Write out equation with unknown isolated 4. Plug in #’s with units 5. Solve, give answer with PROPER UNIT!

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**Formulas Current = Volts/ Resistance I= V/R**

Power is a function of Voltage and current expressed by the equation. P = I x V

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Sample Problem #1 What is the current passing through a 3 W resistance that is connected to a volt battery?

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Sample Problem #1 12 volts/3 ohms= 4 amps

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Sample Problem #2 A 30 amp current is passing through a 4 W resistor, what is the voltage in the circuit?

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Sample Problem #2 30 amps x 4 ohms= 120 volts

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Sample Problem # 3 A 6 v battery pushes electrons through a circuit with a current of 0.3 amps, what is the resistance of this circuit?

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Sample Problem # 3 6 volts/ 0.30 amps= 20 ohms

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Sample Problem #4 A 12 v battery causes a 0.3 amp current to pass through a bulb. A) What is the bulb’s power usage? B) What is the resistance of the bulb?

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**Sample Problem #4 12 volts x 0.3 amps= 3.6 watts**

12 volts/ 0.3 amps= 40 ohms

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Sample Problem #5 A.) How much current passes through a 40 W bulb attached to a 120 v power source? B.) What is the resistance of the bulb?

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**Sample Problem #5 40 watts/ 120 volts= 0.33 amps**

120 volts/0.33 amps= 363 ohms

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Sample Problem #6 A. A 100 W bulb has a 0.2 amp current passing through it, what is the voltage of the power source? B. What is the resistance of the bulb?

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**Sample Problem #6 100 watts/ 0.20 amps= 500 volts**

500 volts/0.20 amps= 2500 ohms

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**Electrical Current Recall**

Name 2 factors or things that affect current? Voltage and Resistance How are resistance and current related to each other? Amps= Volts/ Ohms Ohms= Volts/Amps

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