Download CURRENT Electricity

Current Electricity
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Electricity that flows (negative charges move along a wire)
Electrons need a complete and continuous pathway to move through a circuit
For this to happen, we need:
1) A source of charges (an energy source, such as a battery)
2) A pathway for electrons to flow (a wire)
3) A device that converts some of the energy from the electrons into another form (such as a light
bulb). A device that converts energy is called a load.
We could include the following in the circuit:
4) A device to control the flow (such as a switch)
5) A meter, used to measure a characteristic of the circuit (such as a voltmeter)
Closed circuit : the circuit is continuous; the switch is “on” and the current is flowing
Open circuit : there is a break in the circuit; no current can flow (switch is “off”)
Current:
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An energy source pushes electrons along conducting wires in a circuit
This flow of electrons is called the current
Current: The amount of charge that moves past a point in the circuit each second
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In other words, the number of electrons that move past a point each second
Since this involves a very large number of electrons, scientists have devised a quantity to simplify
this number: the Coulomb (C)
So, current is the number of Coulombs per second
The unit for current is the Ampere (Amps, A)
Measuring Current
 To measure current, we will use an instrument called an ammeter
Voltage (Potential Difference):
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An energy source gives energy to electrons when they begin to flow along a circuit.
The energy given to each electron when it begins to move is called electric potential.
As the electrons move through a load, some electrons give off some of their energy
If we measure their energy before and after a load, or before or after a source, we can measure the
change in energy of the electrons.
This difference is called the potential difference (also called voltage)
The unit for potential difference is volts (V)
Measuring Voltage
 To measure voltage, we will use an instrument called a voltmeter
ELECTRIC CIRCUIT DIAGRAMS
To simplify the drawing of electric circuits, we use a special set of symbols. The drawing of circuits using
these symbols are called schematic circuit diagrams. The symbols of these diagrams are connected by
wires. The wires are drawn as straight lines, with right-angled corners.
SYMBOL
Source
NAME
Battery
Switch (Open)
Control Devices
Switch (Closed)
Fuse
Light bulb
Clock
Electrical Loads
Motor
Thermostat
Resistor
Ammeter
Meter
Voltmeter
Practice: Building Circuits
Using your “Electric Circuit Diagrams” chart to assist you, practice drawing circuits with
the following components:
 Be sure to include the direction of the current (electrons!)
 Put all of the components in the same pathway
1. Battery; 2 light bulbs; 1 motor
2. 2 batteries; 4 light bulbs; 1 resistor; 1 ammeter
3. Battery; switch; fuse; thermostat; 2 light bulbs
4. 2 batteries; 2 switches; 3 light bulbs; 1 resistor
5. battery; 1 switch; clock
6. battery; resistor; light bulb; switch; motor
7. Make up your own circuit! Include at least one item from each of the 4 parts of a
circuit (source, control device; electrical load; meter)
Series and Parallel Circuits:
Series Circuits: ONE path for the electrons to follow
Parallel Circuits: MORE THAN ONE path for the electrons to follow
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Sources can be in series or in parallel.
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Loads can be in series or in parallel.