Lesson 10: Nonrenewable Energy Resources Environmental Science
Energy lesson 10
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Transcript of Energy lesson 10
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Target
To know how to set up a series circuit
Electricity
Thursday 9 February 2017
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A circuit is like a central heating system in a house:
Boiler and pump
radiator
High pressurelow pressure
There is a pump that pushes water round the system. The water everywhere starts to move AT THE SAME TIME.
There are pipes that CARRY the water.
In the pipes the water is FLOWING.
flow ofwater
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An electrical circuit is very similar to a central heating system.The bulb in the circuit is like a radiator. An electrical device uses electrical energy supplied by the circuit.
Instead of a flow of water, electricity flows in an electrical circuit. The wires are like pipes; they carry the electricity(called current) round the circuit.
The electrical current is pushed by the battery, which has the same function as the pump and boiler. The strength of push provided by the battery is called its voltage.
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lamps
This is a simple series circuit. In a simple series circuit, everything is connected in one loop across the terminals of the battery. So there AREN’T any points where the current can split or join (these are called junctions).
This circuit has two lamps connected in series. Circuits are always drawn using straight lines.
Series circuit
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Here are some other simple series circuits:
1. Two resistances (resistors) connected in series.
2. A rheostat (or variable resistor) and a bulb connected in series.
R1 R2
Series circuit
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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
When measuring the current through a component, the ammeter is always connected in series (in the same loop) with that component.
AA
A
Measuring current
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When measuring the voltage across a component, the voltmeter is always connected in parallel with (or across) the component.
V3
V2
V1
We measure the voltage using a device called an voltmeter. In a circuit this is given the symbol V
The voltage supplied by the battery is shared between all the components in a series circuit.
This is still a SERIES circuit.
Measuring voltage
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Series circuit
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A
V
componenthere R
Voltage is measured by connecting the voltmeter across (or in parallel with) the component.
Voltage is measured in volts and the symbol for this is V.
V
Components
Measuring voltage - across a resistance or a bulb
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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.
Experiment: measuring voltage
R
V
V
Circuit 1
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1. Add another resistance (R2) to the circuit as shown.2. Connect the voltmeter across the power supply and
measure the supply voltage. 3. Then measure the voltage across each of the resistances.
R1 R2
V
V1 V2
Circuit 2
Experiment: measuring voltage
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Record your results:
Circuit 1: Voltage (supply) = V
Voltage (R1) = V
Circuit 2: Voltage (supply) = V
Voltage (R1) = V
Voltage (R2) = V
R1 R2
V
V1 V2
R1
V
V
Circuit 1 Circuit2
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The current is the ____ of electricity around the circuit. The _______ is the amount of push.
When two components were put into Circuit 2, the voltage of the supply was the ____ as Circuit 1. However, the voltage across R1 ________ .
The voltage across both components in circuit 2 added to be equal to the _____ voltage.
supply, decreased, voltage, flow, same
Circuit2
R1 R2
V
V1 V2
R1
V
V
Circuit 1 Circuit2
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V1
V2
V3
Measuring voltage in parallel circuits
Connect together the circuit shown above and measure, in turn, the voltage at V1, V2 and V3.
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Write down your results in the table below :
Voltmeter Voltage(V)
V1
V2
V3
Explain anything you notice about the results.
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Target
To know how to set up a parallel circuit
Electricity
Thursday, February 9, 2017
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Parallel circuits
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Parallel and series circuits
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Experiment: measuring current
R1
1
2
A
1. Set up the circuit as shown above.
2. Measure the current using the ammeter at positions 1 and 2.
Circuit 1
A
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R1 R2
1
2
3
A
A
A
1. Add another resistor into the circuit.
2. Now measure the current using the ammeter at positions 1, 2 and 3.
Circuit 2
Experiment: measuring current
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Results
Current Position 1
Current Position 2
Current Position 3
Current Position 1
Current Position 2
Circuit 1
Circuit 2
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Circuit 1
The current at different positions in the circuit, before and after the resistor, was the _____.Current is ___ used up by the components in the circuit.
Circuit 2
Increasing the number of components in the circuit _______ the current. The current at all points in a series circuit is the ____.
same / same / decreased / not
Conclusions
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1. Set up the circuit as shown above.
2. Connect the voltmeter across the power supply and measure the supply voltage. Then measure the voltage across the resistance. Measure the current.
Experiment: cells
R1
V
V
Circuit 1
A
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1. Add an additional battery to the circuit.
2. Connect the voltmeter across the power supply and measure the supply voltage. Then measure the voltage across the resistance. Measure the current.
R1
V
V
Circuit 2
A
Experiment: cells
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Results
Circuit 1: one battery
Circuit 2: two batteries
Supply Voltage
Voltage R1
Current
Supply Voltage
Voltage R1
Current
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Delete the wrong answer:
Increasing the number of batteries / cells increases/decreases the current that flows in the circuit.
The current/voltage depends on the current/voltage.
Conclusions
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1. In a series circuit the current is the same at any point in the circuit.
2. The supply voltage is shared between the components in a series circuit.
3. The current depends on the voltage in ANY circuit.
Summary for series circuits
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Parallel circuits
A parallel circuit is one which contains a point (a junction) where the current can SPLIT (point A) or JOIN (point B). This means that there is MORE than one path around the circuit.
A B
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Measuring current in parallel circuits
A1
A2
A3
A41 2
3
4
1. Place the ammeter, in turn, at positions 1, 2, 3 and 4.
2. Record the ammeter reading at the points in the table shown.
Ammeter Current (A)
A1
A2
A3
A4
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For a parallel circuit, the current that leaves the cell or battery is the same as the current that returns to the cell or battery. The current does NOT get used up by a circuit, just the energy the electrons are carrying.
A1 = A4
The current splits up at the first junction and then joins together at the second junction. If the bulbs are identical then the current will split evenly. If the bulbs are NOT identical, then the current will NOT split evenly. The following is always true for this circuit.
A1 = A2 + A3 =A4
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Energy in circuits
This section deals with the energy transfers in electric circuits.
The most important thing to understand about energy is that it cannot be created or destroyed.
In all devices and machines, energy is transferred from one type to another.
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lamps
When this circuit is connected, chemical energy stored in the battery is transferred via electrical energy to heat and light energy in the bulbs.
The total amount of heat and light energy is the same as the amount of chemical energy lost from the battery.
Energy transfer in electrical circuits
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Notice, most of the energy from the battery does not produce light - most of it is wasted as heat!
chemical energy lost from battery (e.g. 100J)
heat energy of bulb 95 J transferred to
5J transferred to bulb aslight energy
Energy transfer in electrical circuits
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Energy efficiency
We can work out the efficiency of an energy transfer:
x 100
For this bulb
efficiency = (5/100) x 100 = 5%
total energy input
useful energy output%Efficiency =
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Other energy transfers
Batteries can power many things -
What sort of energy is the electrical energy transferred into in these examples?