What happens when certain electrically insulating materials are rubbed with a dry cloth?
Electrons transfer between the insulating material and the cloth
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What charge does the insulating material get?
Positive
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What charge does the cloth get?
Negative
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What is charging by friction?
The process where an insulating material gains electrons and becomes negatively charged and the material that loses electrons is left with a positive charge
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What is an electric current?
A flow of charge due to electrons being forced to move
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What is electric current measured in?
Amperes
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What is electric charge measured in?
Coulombs
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What is the current through a component measured with?
An ammeter
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Where are ammeters always placed in relation to the component?
In series
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What is the potential difference across a component measured with?
A voltmeter
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Where are voltmeters always placed in relation to the component?
In parallel
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What is the potential difference across a component?
The energy transferred to it by each coulomb of charge that passes through it
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What is resistance?
The opposition to current flow
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What is the unit of resistance?
The ohm
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How can the resistance of a component be found?
By measuring the current through and the potential difference across the component
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What does a greater resistance result in?
A smaller current for a given potential difference across the component
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What does ohm's law state?
That the current through a resistor at constant temperature is directly proportional to the potential difference across the resisitor
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What shape is the line on a current-potential difference graph for a filament bulb?
A curve because the resistance of the filament increases as the current increases
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Why does the resistance increase as the temperature increases for a filament bulb?
The metal ions in the filament of the lamp vibrate more as the temperature increases so they resist the passage of electrons through the filament more
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Why does current through a diode flow in one direction only?
In the reverse direction, the diode has a very high resistance so the current is virtually zero
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In a series circuit, what is the current through each component?
The same
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In a series circuit, what is the potential difference across each component?
The potential difference of the supply is shared between all the components in the circuit. So the pd across each component add up to give the pd of the supply
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In a series circuit, what is the total resistance?
The sum of the resistance of each component
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In a parallel circuit, what is the potential difference across each component?
The same
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In a parallel circuit, what is the total current?
The sum of the currents through the separate components
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