Electromagnetism Flashcards
What do unlike and like poles do?
Unlike attract and like repel
Lines of magnetic field can be plotted using what?
A compass
A magnet that has a N and S pole all the time is called a what magnet?
A permanent magnet
What materials are magnetic?
Iron,steel,cobalt and nickel
What is the magnetic field?
The region around a magnet where a force acts on another magnet or magnetic material.
What does the thumb indicate on the thumb rule?
The direction of the current
What do the fingers represent for the thumb rule?
The direction of the magnetic field.
What is force measured in?
Newtons
What does polarity mean?
The poles of the magnet.
What happens to the field around a solenoid?
As the current increases so does the strength of the magnetic field (Paper clip experiment)
What are the two types of magnet?
Permanent or induced magnets
What do step-up transformers do?
Increase the potential difference
What do step-down transformers do?
Decrease the potential difference
What is different about the step-up and step-down transformers?
Step-up transformers have more turns on the secondary coil whereas step-down transformers have more turns on the primary coil.
What is the Transformer equation?
Vp/Vs = np/ns
^input pd/output pd=no. turns on primary/no. secondary
What can be said about the efficiency of transformers
They are almost 100% efficient
Why do transformers only work for Ac?
Because we need a changing magnetic field to induce a potential difference.
What is The National Grid?
A system of transformers and high voltage cables that distribute energy to peoples homes
What is the main problem when getting electricity to homes?
Energy is always lost in the power cables due to the resistance of the wires
What can you say about the amount of energy lost depending on the distance away from the national grid?
The further travelled, the more energy lost.
What, other than using transformers, will reduce energy loss?
Having power stations closer to homes.
Describe the first stage how energy gets to peoples homes.
First electricity from the power station passes through step up transformer which increase the potential difference to 100’s of thousands of volts.
Describe the second stage of energy getting to homes
Less energy is lost through the power cables when pd is high hence the step-up transformer.
Describe the final stage of getting energy to homes
Electricity then passes through the step-down transformer as the pd is far too high so it reduces it to 230V.
