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PHYSICS Mr. BALDWIN ELECTRICITY September 12, 2014

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AIM: How do we determine the equivalent resistance in series circuits?

DO NOW:

Calculate the resistance of a filament in a lightbulb that carries a 400mA current when connected to a 9.0 V battery?

HOME WORK

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BALDWIN

Resistors in Series

A series connection has a single path from the battery, through each circuit element in turn, then back to the battery.

Resistors in Series

The current through each resistor is the same; the voltage depends on the resistance. The sum of the voltage drops across the resistors equals the battery voltage.

Resistors in Series

From this we get the equivalent resistance (that single resistance that gives the same current in the circuit).

AIM: How do we determine the equivalent resistance in parallel circuits?

DO NOW QUIZ: Determine

the equivalent resistance in the circuit

the current in the circuit

the voltage drop across each resistor

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BALDWIN

Resistors in Parallel

A parallel connection splits the current; the voltage across each resistor is the same:

Resistors in Parallel

The total current is the sum of the currents across each resistor:

Resistors in Parallel

This gives the reciprocal of the equivalent resistance:

AIM: How do we measure voltage and current in simple circuits?

DO NOW:

Calculate the equivalent resistance of the circuit?

HOME WORK – handout

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BALDWIN

Ammeters and Voltmeters

- An ammeter measures current;
- A voltmeter measures voltage.
- An ohmmeter measures resistance; it requires a battery to provide a current.

Section

Diagramming Circuits

22.1

- An ammeter measures the current through a circuit component.
- The same current going through the component must go through the ammeter, so there can be only one current path.

- A connection with only one current path is called a series connection.

Section

Diagramming Circuits

22.1

- Any time the current has two or more paths to follow, the connection is labeled parallel.
- The potential difference across the voltmeter is equal to the potential difference across the circuit element.

AIM:Solving problems involving complex circuits?

DO NOW:

Calculate the equivalent resistance of the circuit?

HOME WORK – READ Chapter 36. Prep for QUIZ

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BALDWIN

Recall: The same current passes through all the components; the sum of the potential drop across each component is equal to the potential of the source

Recall: The potential across each component is equal to the potential of the source, the sum of the current across each component is equal to the current in the circuit.

Consider the following diagram. Calculate:a. the equivalent resistance of the resistor combinationb. the current in the circuitc. the potential drop across each resistord. the power dissipated across each resistor

Consider the following diagram. Calculate:a. the equivalent resistance of the resistor combinationb. the current in the circuitc. the potential drop across each resistord. the power dissipated across each resistor

AIM:How do we solve compound circuits?

DO NOW: Write down the formulas for the following:

a. Ohm’s law

b. Resistors in Series

c. Resistors in parallel

d. Power (in terms of I, V and R)

HOME WORK – DO TEXT pg 561: # 29 & 31

TEXT pg. 575. REVIEW QUESTIONS 1 - 10

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BALDWIN