ME6 - Transformers Flashcards

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1
Q

What do transformers do?

A

Change the size of the voltage of an alternating current

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2
Q

What do all transformers have?

A

Two coils, the primary and the secondary, joined with an iron core

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3
Q

What happens when you apply an alternating voltage across a primary coil?

A

The magnetically soft (iron) core magnetises and demagnetises quickly. This induces an alternating voltage in the secondary coil

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4
Q

The ratio between the primary and secondary voltages is the same as what ratio?

A

The ratio between the number of turns on the primary and secondary coils

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5
Q

What are step up transformers?

A

They step the voltage up - they have more turns on the secondary coil than the primary coil

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6
Q

What are step down transformers?

A

They step the voltage down - they have more turns on the primary coil than the secondary

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7
Q

What do you need to know to calculate the output voltage from a transformer?

A

The input voltage and the number of turns on each coil

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8
Q

What is the word equation for transformers?

A

Input (primary) voltage /Output (secondary) voltage = Number of turns on primary/ number of turns on secondary

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9
Q

What are the other two equations you can use for transformers?

A

Vp/Vs = Np/Ns or both equations flipped around

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10
Q

If transformers are nearly 100% what does that mean?

A

Power in = power out

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11
Q

What is the general formula for power supplied?

A

Power = voltage x current or P= V x I

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12
Q

How can you rewrite input power = output power for transformers?

A

VpIp = VsIs

Vp = Primary voltage 
Ip = Primary current 
Vs = Secondary voltage 
Is = Secondary current
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13
Q

What do transformers make more efficient?

A

Transmitting mains electricity

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14
Q

What are the main purposes of using step up and step down transformers?

A

Used when transmitting electricity across the country

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15
Q

Why is the voltage not transmitted efficiently in power stations?

A

It is too low - the lower the voltage the higher the current for a given amount of power, causing the wire to heat up

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16
Q

What are step up transformers used for in the power station?

A

To boost the voltage before it is transmitted

17
Q

What are step down transformers used for in power stations?

A

Used at the end of the journey to reduce the voltage so its more useful and safer to use