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What is a Circuit???A circuit is any path along which electrons can flow

A household circuit provides 120-Volt potential difference

This means – when you plug anything into a wall outlet, one prong has a potential of 120 V, and the other has the potential of 0 V. This causes electrons to flow.

How does this cause a light bulb to work? (light up)

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What is a Circuit???Electrons flow from the prong with the high potential

through the copper wiring

The electrons then flow through the filament of the light bulb, which causes the light bulb to light up

They then continue flowing towards the prong with low potential

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Would the light bulb still light up if the filament were broken?

NO!!!

The electrons MUST have a complete circuit to flow

through

For the continuous flow of electrons, there must be a

complete circuit with NO gaps

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• Current – the flow of electrons

• Resistance – the slowing down of the flow of electrons

• Voltage – produces the flow of electrons.

Circuit Properties

Each property has different parts of a circuit, or circuit elements

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Voltage Source

A voltage source is anything that provides a potential difference

This is an essential component of a circuit

Batteries are a very common voltage source

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Wires

Wires are the conduit through which current flows

Wires are generally made of a highly conductive material like copper

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Resistors

Resistors are small circuit elements that resist (slow down) the flow of electrons in a circuit

Resistors are made out of materials with high resistances, like ceramic

They are generally color coded by value (the bands around them have a meaning)

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Other things can be placed in circuits (lamps, motors – also resistors) (meters – measure voltage, current)

These elements can be placed into a circuit in two different ways.

• Series

• Parallel

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Series Circuits

4 Characteristics

1. Current has a single pathway through the circuit

2. Resistance is cumulative (the sum of all of the resistances in the path)

3. Current in the circuit is equal to the voltage from the voltage source divided by the total resistance in the circuit (Ohm’s Law)

4. Ohm’s Law applies separately to each device, so the voltage drops across each device, according to its resistance

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Series CircuitsDisadvantages:

If several light bulbs are connected in series, and one goes out, what happens to the circuit?

This idea may be familiar to you through some Tree decorating experiences.

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Parallel Circuits

Items connected in parallel, have separate branches, any one of them can allow the electrons to flow through

In a parallel circuit, all of the electrons DO NOT flow through all of the circuit elements

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Parallel Circuits

1. Each device connects the same two points in a circuit, so the voltage is the same across each device

2. The total current in the circuit splits up among the different branches (think of electrons getting to chose which branch they go down), so the current is different across each branch. More current passes through the branches with lower resistance (Ohm’s Law)

3. The total current in the circuit equals the sum of the currents in it’s parallel branches

4. As the number of branches increases, the total resistance decreases.

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Circuit Diagrams

They are used to avoid assembly problems and to essentially pictures of circuits.

battery

resistor

light bulb

switch

M

A

V

Motor

Ammeter

Voltmeter

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