P4 Transformers

What is a transformer made up of?

two coils wrapped around a soft iron core

What does a transformer do?

transform the voltage of alternating currents.

What is a step-up transformer?

increasing the voltage of an electric current

What is a step-down transformer?

decreasing the voltage of an electric current

Why are transformers used to step up the voltage in power lines?

reduce power loss

How do transformers reduce power loss?

because higher voltage means a smaller current

What formula proves that transformers reduce power loss?

P=I²R

P=power

I=current

R=resistance

What is the equation for 100% efficiency in a transformer/

I_p V_p = I_s V_s

I_p= current of primary coil
V_p=voltage of primary coil

I_s= current of secondary coil
V_s=voltage of secondary coil

How does a transformer work?

-An alternating current in the primary coil creates a changing magnetic field.

-The iron core becomes magnetised, transmitting the changing magnetic field to the secondary coil and induces an alternating e.m.f. in it.

-If the secondary coil is part of a complete circuit, this results in a current flowing.

Step-up transformer relationship with number of turns on coil

A step up transformer has more turns on the secondary coil which means the voltage of the secondary is greater than that of the primary.

Step-down transformer relationship with number of turns on coil

A step down transformer has fewer turns on the secondary coil which means the voltage of the secondary is less than that of the primary.

Formula for ratio of coils to voltage

V_p/V_s = N_p/N_s

V_p= voltage of primary coil
V_s=voltage of secondary coil

N_p= number of coils on primary coil
N_s= number of coils on secondary coil