5.3 Capacitors in the real world Flashcards Preview

A-Level Physics EDEXCEL Year 2 > 5.3 Capacitors in the real world > Flashcards

Flashcards in 5.3 Capacitors in the real world Deck (9)
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1
Q

Some uses of capacitors in day to day life?

A

Keyboard keys
Cable to satellite dish/aerial to TV set (coaxial cable)
Coulombmeters

2
Q

What does the setup of a keyboard key look like?

A

Key attached to movable metal plate, below is a squishy insulating material, followed by another metal plate.

3
Q

How does this setup work to deduce which key has been pressed?

A

Upon pressing the metals plates get closer, this changes the capacitance, so that it can now be deduced which key was pressed.

4
Q

How are capacitors used in a coaxial cable?

A

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).

5
Q

How is a coaxial cable a capacitor?

A

Since it has an insulating layer.

6
Q

How can a digital voltmeter be turned into a coulombmeter?

A

Having a capacitor being connected across its terminals (in parallel)

7
Q

Why does this work?

A

The scale of the meter can be adjusted to read nanocoulombs directly.

8
Q

What kind of voltmeter is needed for this to work?

A

A digital voltmeter

9
Q

What happens to capacitance as plates (under key) get closer together? Why

A

The capacitance increases. This is because the electric potential (v) decreases while charge stays the same.

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