ME6 - Transformers Flashcards
What do transformers do?
Change the size of the voltage of an alternating current
What do all transformers have?
Two coils, the primary and the secondary, joined with an iron core
What happens when you apply an alternating voltage across a primary coil?
The magnetically soft (iron) core magnetises and demagnetises quickly. This induces an alternating voltage in the secondary coil
The ratio between the primary and secondary voltages is the same as what ratio?
The ratio between the number of turns on the primary and secondary coils
What are step up transformers?
They step the voltage up - they have more turns on the secondary coil than the primary coil
What are step down transformers?
They step the voltage down - they have more turns on the primary coil than the secondary
What do you need to know to calculate the output voltage from a transformer?
The input voltage and the number of turns on each coil
What is the word equation for transformers?
Input (primary) voltage /Output (secondary) voltage = Number of turns on primary/ number of turns on secondary
What are the other two equations you can use for transformers?
Vp/Vs = Np/Ns or both equations flipped around
If transformers are nearly 100% what does that mean?
Power in = power out
What is the general formula for power supplied?
Power = voltage x current or P= V x I
How can you rewrite input power = output power for transformers?
VpIp = VsIs
Vp = Primary voltage Ip = Primary current Vs = Secondary voltage Is = Secondary current
What do transformers make more efficient?
Transmitting mains electricity
What are the main purposes of using step up and step down transformers?
Used when transmitting electricity across the country
Why is the voltage not transmitted efficiently in power stations?
It is too low - the lower the voltage the higher the current for a given amount of power, causing the wire to heat up
