# Shared Flashcard Set

## Details

OCR - AS Level: Unit 2
Electrons, Waves and Photons
9
Physics
05/21/2013

Term
 What is the value and unit of Planck's constant (h)?
Definition
 6.63E-34 Js
Term
 What is the value and unit of e (elementary charge)?
Definition
 1.6E-19 C
Term
 What is the definition of 'mean drift velocity'? 
Definition
 The average distance travelled by an electron along a wire per unit time  This is in one direction, and is slowed down by collisions with the metallic lattice 
Term
 What is meant by the term 'current'?
Definition
 Rate of flow of charge
Term
 What is the area under a current-time graph? [With a reason]
Definition
 Charge flow, because Q=It
Term
 What is Kirchoff's first law, and what does it show the conservation of?
Definition
 Sum of currents entering a junction is equal to the sum of currents exiting that junction, shows conservation of charge
Term
 The number of electrons per unit volume, is also known as what? (and give the units for this measurement)
Definition
 Number density, measured in m^-3
Term
 What is the number density of semiconductors, relative to conductors and insulators? [e.g. more or less]
Definition
 Semiconductors have more electrons per unit volume than insulators, but less than conductors [they have ~10^18 m^-3]
Term
 State Ohm's Law
Definition
 For a metallic conductor at constant temperature, current through the conductor is directly proportional to potential difference across its ends
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