Magnetism and Electromagnetism Flashcards
Define Magnetic field
Region where magnetic materials experience a force
In which direction do the magnetic field lines go?
From north to south
Define uniform field
Where the field strength (or the force experienced by an object) is the same at every point in the field.
Practical with magnetic fields
Place a magnet underneath a piece of paper and scatter iron filings on top to reveal a magnetic field pattern. Tap the paper gently.
Place compass needles tip-to-tail near a magnet. Record their orientations, to plot the magnet’s field as continuous field lines.
How can magnetism be induced?
If a magnetic material is brought near a magnet, it will act as a magnet. The closer they are, the stronger the induced magnetism will be.
Does electricity create magnetism?
Yes. When an electric current flows through wire it will be magnetic.
2 facts about currents in wires
-The larger the electric current, the stronger the magnetic field
-The direction of the magnetic field depends on the direction of the current.
Magnetism in a straight wire
Concentric circles
Magnetic field around a flat circular coil.
-The magnetic field in the centre is similar to a bar magnet
-Concentric ellipses of magnetic field lines around the coil.
Magnetic field around a solenoid
-Strong and uniform
-Outside of the coil, the field is like the one around a bar magnet.
-The ends of a solenoid act like the north pole and south pole.
-Electromagnet.
What makes a magnetic material soft or hard?
Soft- loses its induced magnetism quickly
Hard- keeps it permanently
-You can increase the strength of a magnetic field around a solenoid by adding a magnetically soft iron core through the middle of the coil.
Define the motor effect
It can happen when you put a current-carrying wire in a magnetic field.
Why does the motor effect occur?
When a current-carrying wire is put between magnetic poles, the two magnetic fields affect one another. The result is a force on a wire (it may move. The charged particles moving through a magnetic field will experience a force, as long as they’re not moving parallel to the filed lines.
What happens when you reverse the direction of the current or magnetic field?
It reverses the direction of the force.
In the left hand rule, what does each finger represent
Thumb=Direction of force
Index=Field
Middle=Current
Define Electromagnetic induction
Creation of voltage in a wire which is experiencing a change in magnetic field
Define the dynamo effect
Using electromagnetic induction to generate electricity using energy from kinetic energy stores.
What are 2 ways in which you can get EM induction?
- Electrical conductor moves through magnetic field.
- Magnetic field through an electrical field changes.
What does each part of the hand represent in the right-hand rule
Thumb=Direction of current
Hand= Magnetic field
What ‘types’ of energy does the chemical energy stores in Power Stations.
Chemical energy store→Thermal energy store→Kinetic energy store→Kinetic energy store. Then transferred away electrically.
Explain the process of creating electricity in power stations.
- Fossil fuel burns in oxygen.
- The energy in its chemical energy store is transferred to the thermal energy store of the water by heating.
- Water boils and forms steam, turns the turbine, transferring energy mechanically to the kinetic energy store of the turbine.
- Turbine revolves, so does the generator. Produces an electric current. The generator transfers energy electrically away from the station via the national grid.
What type of current do transformers use?
Alternating current, so it is constant.
Describe a transformer
They have two coils, the primary and the secondary, joined with an iron core.
Describe the ratio between the voltages and the number of turns
The ratio between the primary and secondary voltages is the same as the ratio between the number of turns on the primary and secondary coils.
