Measuring Voltage and Current

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Transcript Measuring Voltage and Current

Measuring Voltage and Current
• Aims
• Know the units of voltage and current
• Know how to measure voltage and current
Circuit Symbols
A.
B.
C.
D.
E.
Ammeter
Motor
Voltmeter
Bulb
Cell
F.
G.
H.
I.
Battery
Buzzer
Switch closed
Switch open
Draw a Circuit Diagram for the
Apparatus Below
Draw a Circuit Diagram for the
Apparatus Below
Draw a Circuit Diagram for the
Apparatus Below
Measuring Current.
The unit of measure for current is the "amp" which
has the symbol A.
We measure the current using a device called an
ammeter. In a circuit this is given the symbol A
When measuring the current through a
component, the ammeter is always connected in
series (in the same loop) with that component.
A
Measuring Voltage.
We measure the voltage using a device called an
voltmeter. In a circuit this is given the symbol V
When measuring the voltage across a component, the
voltmeter is always connected in parallel with (or across)
the component.
V
1
This is still
a SERIES
circuit.
V2
The voltage supplied by the battery is shared between all
the components in a series circuit
Series Circuit Animation
Experiment: Measuring Voltage
V
Circuit 1
R
V
1. Set up the circuit as shown above.
2. Connect the voltmeter across the power supply and
measure the supply voltage.
3. Then connect the voltmeter across the resistance (R)
and measure this voltage.
Basic ideas…
Electric current is when electrons start to flow around a
circuit. We use an _________ to measure it and it is
measured in ____.
Voltage is how big the push on the electrons is.
We use a ________ to measure it and it is
measured in ______, a unit named after Volta.
Resistance is anything that resists an electric current. It is
measured in _____.”
(Words: volts, amps, ohms, voltage, ammeter, voltmeter)
Energy changes
To describe an energy change for a
light bulb we need to do 3 steps:
1) Write down the
starting energy:
3) Write down
what energy types
are given out:
2) Draw an arrow
Electricity
Light + heat
What are the energy changes for the following…?
1) An electric fire
2) A rock about to drop
3) An arrow about to be fired
Electrical Energy
Consider a simple circuit:
The job of the battery is
to convert ______ energy
into _________ energy…
The job of the bulb is to
convert the _________
energy it receives from
the battery into ______
energy.
Words – electrical (x2), light, chemical
Hi. I’m Ernie Electron
and I’m going to show
you how I get energy
around a circuit.
Electrical Energy
Energy
Hi. I’m Ernie Electron
and I’m going to show
you how I get energy
around a circuit.
Electrical Energy
Energy
Hi. I’m Ernie Electron
and I’m going to show
you how I get energy
around a circuit.
Electrical Energy
Energy