5.3 Capacitors in the real world Flashcards
Some uses of capacitors in day to day life?
Keyboard keys
Cable to satellite dish/aerial to TV set (coaxial cable)
Coulombmeters
What does the setup of a keyboard key look like?
Key attached to movable metal plate, below is a squishy insulating material, followed by another metal plate.
How does this setup work to deduce which key has been pressed?
Upon pressing the metals plates get closer, this changes the capacitance, so that it can now be deduced which key was pressed.
How are capacitors used in a coaxial cable?
The whole cable acts as a cylindrical capacitor. The total capacitance can be calculated when knowing the length of cable and this allows engineer to reduce reflections of signal (these may appear as shadows on TV).
How is a coaxial cable a capacitor?
Since it has an insulating layer.
How can a digital voltmeter be turned into a coulombmeter?
Having a capacitor being connected across its terminals (in parallel)
Why does this work?
The scale of the meter can be adjusted to read nanocoulombs directly.
What kind of voltmeter is needed for this to work?
A digital voltmeter
What happens to capacitance as plates (under key) get closer together? Why
The capacitance increases. This is because the electric potential (v) decreases while charge stays the same.
