12.1- CURRENT AND CHARGE Flashcards
What must a circuit be like to make an electric current pass round the circuit?
circuit must be complete + there must be source of p.d. i.e. battery in circuit
What is the electric current?
rate of flow of charge in wire or component
What is the current due to?
passage of charged particles
What are the charged particles responsible for current referred to as?
charge carriers
What are the charge carriers in metals?
conduction electrons
What do the conduction electrons in metals do?
move about inside metal, repeatedly colliding with each other + fixed positive ions in metal
What is the charge carried by when current is passed through a salt solution?
charge carried by ions
What are ions?
charge atoms or molecules
What is a simple test for conduction of electricity?
meter shows non-zero reading whenever any conducting material connected in circuit
battery forces charge carriers through conducting material + causes them to pass through battery + meter
Simple test for conduction of electricity with metal?
electrons enter battery in positive terminal after passing through metal + ammeter, + leave at negative terminal to continue cycle again
What is the convention for direction of current in a circuit?
from positive (+) to negative (-)
What is the unit for current?
ampere (A)
What is the unit for charge?
coulomb (C)
Equation for change in charge? (with current)
ΔQ= IΔt
What are the electrical terms materials can be classified in? (3)
conductors, insulators, or semiconductors
What are electrons like in an insulator?
each electron attached to an atom + cannot move away from atom
What happens when a voltage is applied across an insulator?
no current passes through insulator
Why does no current passes through an insulator when a voltage is applied across it?
as no electrons can move through insulator
What are electrons like in a metallic conductor?
most electrons attached to atoms but some delocalised- delocalised electrons are charge carriers in metal
What happens when a voltage is applied across a metal?
conduction electrons attracted towards positive terminal of metal
What happens to the number of charge carriers as temp increases in a semiconductor?
number of charge carriers increases with an increase of temp
What happens to resistance as number of charge carriers increases with an increase of temp in semiconductors?
resistance of semiconductor decreases as temp raised
What is a pure semiconducting material referred to as?
intrinsic semiconductor
Why is a pure semiconducting material referred to as an intrinsic semiconductor?
as conduction due to electrons that break free from atoms of semiconductor
