Transcript Electric current is measured in units called amps

Current and Voltage
Starter
• How do we measure electrical charge (Q)?
Units of Electric Current
• Electric current is measured in Amps (A)
• Very small currents can be measured in
milliamps (mA)
• 1000mA = 1A
• 500mA = 0.5A
• 1mA = 0.001A
Current
Electric current is measured in units called amps (A).
The electric current is not used up by the components in a circuit
but it transfers energy from the voltage source to the various
components making up the circuit.
Electric current is measured using an ammeter.
Current
Electric current is measured in units called amps (A).
The electric current is not used up by the components in a circuit
but it transfers energy from the voltage source to the various
components making up the circuit.
Electric current is measured using an ammeter.
The ammeter is placed in series within the circuit.
Current in a series circuit
If the current
here is 2
amps…
The
current
here will
be…
The current
here will
be…
And the
current
here will
be…
In other words, the current in a series
circuit is THE SAME at any point
Measuring current I
Set up the circuit shown below……
…and then record the current using an ammeter
in the places shown below.
What do you notice about the readings?
The current is the same for each ammeter.
A
A
A
Current in a parallel circuit
A PARALLEL circuit is one where the current has a “choice
of routes”
Here comes the current…
Half of the current will go
down here (assuming the
bulbs are the same)…
And the rest will
go down here…
Measuring current II
For a parallel circuit, the current that leaves the cell or battery is the same
as
the
that
returns
to at
the
cellreadings?
or battery.shown.
The current does not get
…then
What
record
you
the
notice
current
about
the
the
locations
Setcurrent
updo
the
circuit
shown
below……
used up by a circuit, just the energy the electrons are carrying. At the
junction of the circuit we say that current is conserved.
A1 = A4
A1
Ammeter
Current
(A)
A1
A2
A3
A4
0.8
0.4
0.4
A4
A2
A3
The sum of the currents in the branches of a
parallel circuit is the equal to the current that
leaves the cell or battery.
A1 = A2 + A3 =A4
0.8
Current in a parallel circuit (with identical bulbs)
If the
current
here is 6
amps
And the
current here
will be…
The current
here will be…
The current
here will be…
The current
here will be…
Use the following interactive animation to check your
understanding of current and voltage in different circuits.
Measuring Potential difference (voltage)
Potential difference is measured using a voltmeter.
The voltmeter is placed in parallel to the circuit.
Measuring voltage I
For a series circuit, the sum of the voltages for each component
is equal
todo
theyou
voltage
across
the
orlocations
battery. shown.
Set
up
the
apparatus
as shown……
…then
What
record
notice
the voltages
about
the
atcell
the
readings?
V1 = V2 + V3
V1
NB Voltmeters are
connected in parallel
V2
V3
Voltmeter
Voltage
(V)
V1
V2
V3
1.5
0.75
0.75
Series circuit
Measuring voltage II
V1
For
..measure
parallel
circuit,
voltage
theat
Setado
up
thethe
apparatus
What
you
notice
about
the
voltage
locations
across
shown.
the
as
shown….
your
readings?
cell/battery is the same
as the voltage across
each branch.
V1 = V2 = V3
V2
V3
Voltmeter
Voltage
(V)
V1
V2
V3
1.5
1.5
1.5
Parallel circuits
What is potential difference
(voltage)?
• It is the energy transferred per unit charge
passed and hence that the volt is a joule
per coulomb.
Plenary – P2.4c