Transformers (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Physics): Revision Note

Structure of a transformer

Extended tier only

• A transformer is a device used to change the size of an alternating voltage or current

  • This is achieved using the generator effect

• A basic transformer consists of:

  • a primary coil

  • a secondary coil

  • a soft iron core

• Iron is used because it is easily magnetised

Construction of a simple transformer

A simple transformer is made up of a primary coil and a secondary coil wound on a soft iron core

Step-up & step-down transformers

Extended tier only

• A transformer consists of a primary and secondary coil

  • The primary coil is the first coil

  • The secondary coil is the second coil

Step-up transformer

• A step-up transformer: 

  • increases the voltage of a power source $\left(V_s>V_p\right)$

  • has more turns on the secondary coil than on the primary coil $\left(N_s>N_p\right)$

A step-up transformer has more turns on the secondary coil which increases the size of the voltage

Step-down transformer

• A step-down transformer: 

  • decreases the voltage of a power source $\left(V_s<V_p\right)$

  • has fewer turns on the secondary coil than on the primary coil $\left(N_s<N_p\right)$

A step-up transformer has fewer turns on the secondary coil which decreases the size of the voltage