Computer Discs
Is aluminium attracted by magnets? In what conditions it is?
Yes, but only if there is movement.
The opposite word for "attract" in magnet is?
repel
Does silver attract magnets?
No
In speakers the electric energy is transformed to what type of energy to make vibration?
kinetic energy
What is the English word for "elektrický proud"?
Electric current
What is a magnetic field?
It is an area of magnetic force of a magnet.
What does the MagLev shortcut stand for?
Magnetic Levitation
Why must patients remove metal objects before an MRI scan?
Because the strong magnetic field can pull metal objects, which is dangerous and can also disturb the scan.
Does copper attract magnets?
Only if there is electric current going through the vire.
What two metals did we use for the lemon / potato battery?
Zinc and Copper
How do we call a very strong magnet (silver color, used in our experiments and also in computers)?
Neodymium magnet
Why don’t maglev trains need wheels in high speed?
Because magnets lift the train above the track, so it floats and doesn’t touch the rails.
What kind of particles in the body does MRI mainly work with?
Hydrogen atoms, because they are very common in the body (especially in water).
What creates the magnetic field inside the speaker coil?
An electric current flowing through the coil.
What is the difference in function of LED lightbulb and normal (old-fashioned) incandescent light bulb?
The incandescent lightbulb is heating up a wire and also produces heat and it has lower efficiency. The LED lightbulb works because electrons jump from one state to another and it does not produce heat so it is more efficient.
What do the 0 and 1 physically represent in a magnetic hard drive?
They represent different directions of magnetization in tiny regions of the disk.
What speed do the fastest maglev test trains in Japan exceed?
600 km/h
What is the main job of the strong magnet in an MRI machine?
It lines up hydrogen atoms in the body so the machine can measure signals from them.
What part of a speaker actually moves to create sound?
The diaphragm (or cone) moves back and forth to vibrate the air and produce sound.
What is the difference between conductor and insulator?
Conductor is able to carry electric current and insulators are not.
Why doesn’t a hard drive lose all its data when the power is turned off?
Data is stored as magnetic directions in tiny domains, and these directions remain stable without electricity. The material “remembers” its state until a new magnetic field changes it.
If a maglev train accidentally touched the track, what would immediately change in how it moves, and why?
If it touches the track, friction appears, which slows the train down and causes heat and wear.
Why can an MRI scan show different tissues (like muscle vs brain) if all of them contain hydrogen atoms?
Different tissues make hydrogen atoms return to alignment at different speeds and release different signals. The MRI detects these differences, which allows it to distinguish between tissues.
What happens inside a speaker when you turn the volume up, and why does the sound get louder?
Turning up the volume increases the electrical signal. This creates a stronger magnetic force in the coil, making it move more. The diaphragm vibrates more strongly, producing bigger sound waves, which we hear as louder sound.
Why are some materials good conductors of electricity (like iron or copper) and others (like wood or plastic) are not?
Because metals and other conductors have free electrons which can move in the direction of the electric potential and therefore carry electric current.