current, voltage and resistance
DESCRIPTION
Current, voltage and resistance. Revise the following: Circuit symbols Circuit diagrams Current and voltage in series circuits Current and voltage in parallel circuits. Circuit symbols. Current, voltage and resistance. Current = the rate of flow of electrons in a circuit - PowerPoint PPT PresentationTRANSCRIPT
Current, voltage and resistanceRevise the following:
• Circuit symbols• Circuit diagrams• Current and voltage in series circuits• Current and voltage in parallel
circuits
Circuit symbols
Current, voltage and resistance• Current = the rate of flow of electrons in a
circuit
• Voltage/potential difference = the difference in electrical potential energy between two points in a circuit. Potential difference is also called voltage
• Resistance = a measure of how hard it is for electrons to move in an electrical circuit.
A A
A
1 A
1 A
1 A
Current in a series circuitIn a series circuit, the current flows
through one continuous pathway so the current is the same in all parts of a series
circuit.
In a series circuit, the voltage supplied by the battery is shared by the components so the sum of the potential difference across the components equals the battery
voltage.
V
VV
6 V
3 V 3 V
As more bulbs are added in series, each bulb has less potential difference and so the bulbs become
dimmer.
Voltage in a series circuit
In a parallel circuit, the current divides at the point where the circuit branches and then recombines to
complete the circuit so the current is not the same in all parts of a parallel circuit.
A A
A
A
1 A
1 A
2 A 2 A
Current in a parallel circuit
• In a parallel circuit, the potential difference across each bulb is the same as the potential difference across the battery. V
V
V6 V
6 V
6 V
• This means that all the bulbs have the same brightness, and they are brighter than the same number of bulbs in a series circuit. • This also means that the battery will run down faster in a parallel circuit.
Voltage in parallel circuits
Georg Ohm (Ohm’s Law)
• It was such an important discovery in electricity that the unit of resistance is called the ohm.
• The formula used to calculate Resistance is called Ohm’s Law
• This unit is represented by the symbol Ω.
• Resistance is a measure of how hard it is for electrons to move in an electrical circuit.• In 1827 a German physics and maths
teacher Georg Ohm discovered a connection between current, voltage and resistance
Ohm’s law is usually written as:
Voltage is measured in volts (V). Current is measured in amps (A).
Resistance is measured in ohms ().
This formula can also be written as:
voltage = current x resistance V = I x R
resistance = R =
voltagecurrent V I
What is the formula/equation for Ohm’s law?
Current-voltage graphs
A resistor at constant temperature
Potential difference isdirectly proportional to
current.As pd/voltage doubles,
current doublesAs pd/voltage triples,
current triples
Filament lamp
A smooth curved line which levels
off
DiodeNo current when
pd/voltage is negative. When
pd/voltage reaches a certain positive voltage, current increases and is
directly proportional to pd
Resistance...