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Electrical CircuitsElectrical Circuits

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Drawing CircuitsDrawing Circuits

1) A cell, a bulb and a switch “in series”

2) A battery of cells, a switch and two bulbs in series

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Measuring electric currentMeasuring electric currentWe can measure the amount of electric current flowing through a circuit using a device called an “ammeter”.

A

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Current in a series circuitCurrent in a series circuit

If the current here is 2 amps…

The current here will be…

The current here will be…

And the current here will be…

In other words, the current in a series circuit is THE SAME at any

point

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Changing the currentChanging the current

If a battery is added the current will ________ because there is a greater _____ on the electrons

If a bulb is added the current will _______ because there is greater ________ in the circuit

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Parallel circuitsParallel circuitsA parallel circuit is one where the current has a “choice of routes”:

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Current in a parallel circuitCurrent in a parallel circuit

A PARALLEL circuit is one where the current has a “choice of routes”

Here comes the current…

And the rest will go down here…

Half of the current will go down here (assuming the bulbs are the same)…

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Current in a parallel circuitCurrent in a parallel circuit

If the current here is 6 amps

The current here will be…

The current here will be…

The current here will be…

And the current here will be…

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Advantages of parallel circuits…Advantages of parallel circuits…

There are two main reasons why parallel circuits are used more commonly than series circuits:

1) Extra appliances (like bulbs) can be added without affecting the output of the others

2) If one appliance breaks it won’t affect the others either

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FusesFuses

Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.

Words – large, harm, safety, melt, live, circuit, fuse