• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/9

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

9 Cards in this Set

  • Front
  • Back

Charges in good electrical conductors (metal)

Charges move relatively freely

Charges in insulators (glass and ceramics)

No mobile charges

Charges in semi conductors

Limited number of mobile charges

Examples of semi conductors

Silicon


Germanium

What happens to resistivity as semi conductor is heated

Some vibrational energy is transferred to atomic electrons


Some of these electrons become free to move through the material


As temp increases


Number of mobile charge carriers increases


So resistivity decreases

Rate of change of resistivity compared to metal

Rate of change of resistivity with temperature > rate of change of resistivity of a metal


Large negative number

Thermistors

Resistance decreases, temperature increases (NTC thermistors)

Uses of NTC thermistors

Car thermometers


Fridges, toasters, hairdryers (thermometers)


In circuits -> prevent a current surge i

Light dependent resistors

Semi conductors with small amounts of another substance (ie galium arsenide)


Electrons absorb energy from light as light intensity increases


More electrons mobile, resistivity decreases