3.7.5.6 - The Operation Of A Transformer Flashcards
What are transformers?
Devices that make use of electromagnetic induction to change the size of the voltage for alternating current.
How do transformers work?
- an alternating current flows through the primary coil inducing magnetic flux across the core.
- the rapidly changing magnetic flux in the core passes through the secondary coil inducing an alternating voltage of the same frequency but different voltage.
What does a step up transformer do?
Increases the voltage by having more turns on the secondary coil than the primary.
What does a step down transformer do?
Reduces the voltage by having fewer turns on the secondary coil than the primary.
What are eddy currents?
Looping currents induced by the changing magnetic flux.
What do eddy currents cause?
They create a magnetic field that acts against the field that induced them, reducing the field strength. They also dissipate energy by generating heat.
What can the effect of eddy currents be reduced by?
Laminating the soft iron core.
What problems does resistance cause in transformers?
Heat is generated in the coils.
How can you reduce the effect of heat in the coils?
Use low resistance wires.
How is energy lost by the core?
Energy is needed to magnetise and demagnetise the core, and this energy is wasted as it heats the core.
How can you reduce the heating effect in the core?
Use a magnetically soft material that easily magnetises and demagnetises - iron.
How is power lost in power lines?
Due to losses due to heating in the cables.
How can you reduce energy loss in power cables?
Use cables with lowest possible resistance. As P=IV use a high voltage as that will also result in low current.
