Magnetism and Electromagnetism Flashcards
How does a compass work?
Inside a compass is a tiny bar magnet. The north pokle of this magnet is attracted tot eh south pole of any other magnet it is near. So the compass points in the direction of the magnetic field it is in.
What is an induced magnet?
Induced magnets are magnetic materials that turn into a magnet when they’re put into a magnetic field. The force between permanent and induced magnets is always attractive. When you take away the magnetic field, induced magnets quickly lose their magnetism (or most of it) and stop producing a magnetic field.
When a current flows through wire…
When a current flows through wire, a magnetic field is created around the wire.
What can you use to work out the direction of the magnetic field depending on the direction of current?
The right-hand thumb rule.
What is an electromagnet?
A solenoid with an iron core (induced magnet).
The solenoid is a coil of wire that increases the strength of the magnetic field that a wire produces. This is because the lines are pointing in the same direction and are very close to each other. Electromagnets can be switched on or off making them very useful in some circuits.
What is the motor effect?
When a current-carrying wire (or any other conductor) is put between magnetic poles, the magnetic field around the wire interacts with the magnetic field it has been placed in. This causes the magnet and the conductor to exert a force on each other. It can cause the wire to move.
How can you identify the direction of the field, current and resultant force?
Using Fleming’s left-hand rule.
What is the generator effect?
The induction of a potential difference (and current if there’s a complete circuit) in a wire is moving relative to a magnetic field, or experiencing a change in magnetic field.
What is the function of an oscilloscope?
Oscilloscopes show how the potential difference generated in the coil changes over time.
What are transformers and their function?
Transformers change the size of the potential difference of an alternating current. They all have two coils of wire, the primary and secondary, joined with an iron core.
How does a transformer work?
When an alternating pd is applied across the primary coil, the iron core magnetises and demagnetises quickly. This changing magnetic field induces an alternating pd in the secondary coil. If the second coil is part of a complete circuit, this causes a current to be induced. The ratio between the primary and secondary potential differences is the same as the ratio between the number of turns on the primary and secondary coils.
