All You Need To Be An Inventor Is A Good Imagination and A Pile of Junk. - Thomas Edison
All You Need To Be An Inventor Is A Good Imagination and A Pile of Junk. - Thomas Edison
All You Need To Be An Inventor Is A Good Imagination and A Pile of Junk. - Thomas Edison
inventor is a good
imagination and a pile
of junk.
-Thomas Edison
I=V/R
I = Current
(Amperes) (amps)
V = Voltage
(Volts)
R = Resistance
Georg Simon Ohm (1787-1854) (ohms)
How you should be
thinking about electric
circuits:
Voltage: a force
that pushes the
current through the
circuit (in this
picture it would be
equivalent to
gravity)
How you should be thinking
about electric circuits:
Resistance:
friction that
impedes flow of
current through
the circuit (rocks
in the river)
How you should be thinking
about electric circuits:
Parallel circuit
Many paths for electricity
1 light goes out and the others
stay on
1
2
Place two bulbs in parallel. What do you
notice about the brightness of the bulbs?
Add a third light bulb in the circuit. What do
you notice about the brightness of the bulbs?
Remove the middle bulb from the circuit.
What happened?
measuring current
Electric current is measured in
A
measuring current
This is how we draw an ammeter in a circuit.
A A
V
measuring voltage
This is how we draw a voltmeter in a circuit.
V
V
SERIES CIRCUIT PARALLEL CIRCUIT
Measure the current and voltage across each circuit.
Use Ohm’s Law to compute resistance
Series Circuit
Parallel Circuit
PARALLEL CIRCUIT
2A 2A
• current is shared
between the 1A
components
1A
fill in the missing ammeter readings.
4A
? 3A
? 3A
1A
?
4A
?
4A 1A
1A
?
The circuit is no longer complete, therefore current can not flow
Parallel Circuits
both ends of a component are connected
e.g. household lighting
copy the following circuits and fill in the
missing ammeter readings.
4A
? 3A
? 3A
1A
?
4A
?
4A 1A
1A
?
measuring voltage
Different cells produce different voltages. The
bigger the voltage supplied by the cell, the bigger the
current.
V V
V
series circuit
• voltage is shared between the components
3V
1.5V 1.5V
parallel circuit
• voltage is the same in all parts of the circuit.
3V
3V
3V
measuring current & voltage
a)
6V
4A A
V V
A
measuring current & voltage
b)
6V
4A A
V
A
answers
a) b)
6V
6V 4A 4A
6V
4A 4A
3V 3V 2A
4A
6V
2A
One Volt is a Joule per Coulomb (J/C)
One Amp of current is one Coulomb per
second (6.24 x10^18 electrons/second).
If I have one volt (J/C) and one amp (C/s), then
multiplying gives Joules per second (J/s)
this is power: J/s = Watts
So the formula for electrical power is just: