Series and Parallel Circuits
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  • Introduction
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There are two types of electrical circuit: series and parallel.

 

In series circuits, the components are connected in one loop. The current that flows through all the components is the same. The diagram below shows a series circuit, where two bulbs are connected in series. If one breaks, the other one will not light, because there is only one loop.

 

 

When there is more than one loop in the circuit, the components are connected in parallel. The diagram below shows two bulbs connected in a parallel circuit. If one breaks, the other one will still work, because there are two loops, so the current flowing through them is split in two. Christmas tree lights are connected in parallel, so if one breaks, the others can still be used.

 

 

Ammeters measure current in amperes or amps (A). Ammeters are always connected in series. Voltmeters measure voltage, which is the potential difference (difference in electrical energy) and drives the current flow. Voltage is measured in volts (V). A voltmeter is always connected to a circuit in parallel to the component with the voltage to be measured.

Current in a series circuit is the same everywhere, so the ammeter will show the same reading anywhere you connect it. If you add more cells, the current will increase. In a parallel circuit the current splits between the different branches.

 

It is important that you familiarise yourself with these electrical symbols:

 

 

Now we will go through some questions on series and parallel circuits.

  • Question 1
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Identify whether this circuit is series or parallel:

 

series

parallel

  • Question 2
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Identify whether this circuit is series or parallel:

 

series

parallel

  • Question 3
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In a series circuit of three bulbs, one bulb breaks. Will the other two work?

yes

no

  • Question 4
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Give an example of a circuit used at home where, if one bulb breaks, the others will still work.

toaster

electric cooker

Christmas tree lights

  • Question 5
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What instrument is used to measure current?

voltmeter

ammeter

currentmeter

  • Question 6
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What is the unit of measurement for voltage?

amps

volts

amperes

  • Question 7
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How is a voltmeter connected to a circuit?

in series

in parallel

  • Question 8
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What circuit component is shown in this diagram?

 

battery

cell

motor

  • Question 9
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The ammeter in the circuit above reads a current of 0.2 A. What will its reading be if you move it between the switch and the cell, provided that the switch is closed and current can flow through it?

0 A

0.4 A

0.2 A

  • Question 10
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What happens to the current in a parallel circuit?

it is the same along the circuit

it splits between the different branches

It increases to cover all branches

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