Transcript current & charge

What we will do today
• State what is meant by electric
current.
• State the difference between
conductors and insulators.
• State how we measure electric
current.
• State how we can measure electric
charge.
What is Electric Current?
• In a conductor, electrons are allowed to
move freely.
• An electric current is a flow of electric
charges, usually electrons.
• Electrons are very small negatively charged
particles.
• In a closed circuit electric current moves
from the negative terminal to the positive
terminal of a battery or power source.
Conductors and Insulators
• Conductors – allow electric current to flow
through.
• E.g metals and carbon
• Insulators – do not allow electric current
to flow through.
• E.g. non-metals like air, plastic & wood
• Super Electric Human (India) Who can
Conduct High Voltage Electricity Through
his Body.FLV - YouTube
Measuring Electric Current
• An ammeter is an instrument that
measures electric current.
• Electric current has the unit amperes
(A).
Measuring Electric Charge
• Electric ‘current’ is a flow of electric
‘charge’ around a circuit.
• We find that the relationship
between the two is given as:
Charge = Current x time
Q=It
• Charge is measured in Coulombs (C).
Example 1
• I=5A
• t = 30 s
• Q=?
Example 2
• I=?
• t = 5 mins
• Q = 150 C
Example 3
• I = 100 mA
• t=?
• Q=5C
2005, Qu: 9