Transcript Electric Current Synchronous Session

Electric Current
In this session we will,
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Review how we measure electric charge
Discuss voltage and electric current
Look at electric current in batteries
Review Ohm’s Law
Before we begin, let’s discuss. .. .
• How do materials develop electric charge?
• Under what conditions does electric
charge flow?
Coulombs
• Coulomb = standard unit of electric charge
• In other words, the amount of electric charge
possessed by an object is measured in
coulombs.
• One coulomb = 6 billion billion electrons, or
about the amount of charge that flows through a
12-watt light bulb.
– Shows you how tiny electrons are
Coulomb’s Law
Volts
• Voltage exists when there
is an imbalance in charge
• If two objects have
different amount of
charge, there is voltage
between them
• For example, standard
battery has a voltage
difference of 1.5 volts
between its positive and
negative terminals
• Volts expressed in
joules/coulomb
Review To This Point
• In a 12-volt car
battery, every
coulomb of charge
that moves from one
side to the other does
________ joules of
work.
Ohm’s Law
• Electric current is driven by ________.
• Electric current is measured in ______,
which is dependent on _______ and
______.
• Electrical resistance is measured in
______.
• Ohm’s Law: I = V/R, where I is amperes, V
is voltage, and R is resistance
Ohm’s Law Triangle
• To calculate voltage, V: put
your finger over V,
this leaves you with I R, so the
equation is V = I × R
• To calculate current, I: put
your finger over I,
this leaves you with V over R,
so the equation is I = V/R
• To calculate resistance, R: put
your finger over R,
this leaves you with V over I,
so the equation is R = V/I
Ohm’s Law Practice
• 1) 3 volts is applied over a 6 ohm resistor. What
is the current in amperes?
• 2) A lamp connected to a 6 volt battery passes a
current of 0.06 amperes. What is the lamp’s
resistance?
• 3) A 1200 ohm resistor passes a current of 0.2
amperes. What is the voltage?
Questions?