ohms%law%% - pbworks
TRANSCRIPT
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Ohms%Law%%
BTEC%%
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Key terms
• Current is the flow of electrons around a circuit.
• Voltage is the driving force that pushes the current around.
• Resistance is anything in the circuit that slows down the flow.
• Voltage pushes and the resistance is opposing it, together they decide what the current will be.
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What%is%Ohms%Law?%
• Ohm's Law describes the relationship between voltage, current and resistance in a simple electrical circuit.
• The law is named after early 19th century German physicist, George S Ohm.
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Georg Ohm (1789-1854), a German Physicist.%
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Ohms%law%
• Ohm%found%that%the%current%in%a%circuit%is%directly%propor<onal%to%the%voltage%and%inversely%propor<onal%to%the%resistance%in%the%circuit.%%
%Can%you%think%of%an%equa<on%that%relates%to%all%3?%
Think%about%their%symbols%%%
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Ohms%law.%
The%three%truths%in%Ohm's%Law%are:%%• if%resistance%remains%the%same,%the%current%flow%goes%up%or%down%if%voltage%goes%up%or%down%%
• when%resistance%goes%up,%the%current%goes%down%so%long%as%the%voltage%remains%the%same%%
• and%when%resistance%goes%down,%current%goes%up%if%the%voltage%is%s<ll%the%same.%%
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Fill%the%gaps%%
The%three%truths%in%Ohm's%Law%are:%%• if%__________remains%the%same,%the%current%flow%goes%up%or%down%if%voltage%_______or%down%%
• when%resistance%goes%up,%the%_________down%so%long%as%the%voltage%___________%the%same%%
• and%when%resistance%goes%down,%current%goes%up%if%the%________________.%%
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Key terms
• Current is the flow of electrons around a circuit.
• Voltage is the driving force that pushes the current around.
• Resistance is anything in the circuit that slows down the flow.
• Voltage pushes and the resistance is opposing it, together they decide what the current will be.
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Crea<vity%%
Senario you have been selected to explain the relationship between V I &R to a class of year 5 students who are visiting STS for the afternoon.
How could you show what is happening inside the wires with resistance?
Be creative.!!!
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Measured in Volts (V).
Measured in Ohms(Ω). Measured in Amps (A).
V#
A#Ω#
V = I x R
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P = V x I
V = I x R
I = V ÷ R
Power is the amount of energy consumed or released by a circuit. Power can easily be found if you know the voltage and the current.
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Calcula<ons%%
• Calculate%the%voltage%in%a%circuit%when%the%current%is%5.4%amps%and%the%resistance%is%6%Ohms.%
• Calculate%the%resistance%when%The%voltage%is%12%volts%and%the%current%is%5%amps.%
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A#
V%
Variable Resistor
Ammeter
Voltmeter
Bulb
Cell
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Voltage (V) volts Current (I) Amps Resistance (R) ohms
Use the table below to record your results. Draw a sketch of your circuit below
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• How%should%a%voltmeter%be%connected%in%a%circuit?%%%%
• An%Ammeter?%%%%%%%%%%%%%%%%%%%%%%%%%%%Grade%C%
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• What%is%another%name%for%Voltage?%%%%%%%(Grade%C)%
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• Draw%a%simple%circuit%that%contains%a%cell%a%bulb%an%ammeter%and%a%voltmeter.%%%%%(Grade%C)%
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• What%was%the%man’s%name%that%discovered%the%rela<on%ship%between%VI&R.%%%%%%
(for%fun)%
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• Calculate%%the%current%when%the%voltage%is%6%v%and%the%resistance%3.2%ohms.%
• Show%all%working.%
(B)%%
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• Calculate%the%power%(P)%%%%%%%%%%%%%%%%%%%%%%%%%%%of%the%circuit%when%the%voltage%is%240V%and%the%current%is%14amps.%
• (Grade%A)%
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Circuit Symbols
%b% M%#%b%
Power Supply Open Switch Closed Switch
Fixed resistor Variable resistor Diode%%
LED LDR Motor
Thermistor Fuse Heater