electricity Flashcards

1
Q

what is emf

A

the total work done by a cell per coloumb of charge

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2
Q

what is ohm’s law

A

the pd across a conductor will be proportional to current as long as physicial conditions remain constant

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3
Q

what is the voltage across components that have work done on them by the current called

A

The potential difference

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4
Q

what is the terminal potential difference

A

the voltage across the terminals of a battery

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5
Q

what can internal resistance be thought of as

A

the resistance to the flow of current inside the power supply itself

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6
Q

how is resitance related to length

A

resistance is proportional to length

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7
Q

how is resistance related to area

A

resistance is inversly proportional to area

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8
Q

what is the relationship between a thermistor and increasing temperature

A

the resistance of the thermistor decreases

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9
Q

what is the relationship of an LDR and increasing light intensity

A

the resistance of the LDR increases

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10
Q

how would you measure the emf of a battery/cell

A

voltmeter across the terminals of the cell with nothing else connected to it

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11
Q

why must a voltemeter have very high resistance

A

so there is virtually no current

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12
Q

what is resistance

A

a measure of how difficult it is for charge carriers to pass through a component

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13
Q

what happens to the resistance of a metal conductor when it’s temperature increases

A

it’s resistance increases when it’s temperature increases

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14
Q

what is a superconductor

A

a material with zero resistivity at or below critical temperature

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15
Q

what is the temperature coefficient of a semi-conductor

A

negative temperature coefficient resistance decreases with increasing temperature

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16
Q

what is the current law at junctions

A

at any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction

17
Q

what is the rule for current entering a component for components in series

A

the current entering a component is the same as the current leaving the component

18
Q

what is the rule for current passing through two or more components in series

A

current passing through two or more components in series is the same through each component

19
Q

what is the net emf of two cells in opposite directions in series

A

the differences between the cells

20
Q

what is the net emf of two cells in the same direction in series

A

the sum of the invdividual emfs of the cells

21
Q

what is a potential divider

A

it consists of two or more cells in series with each other

with a source of fixed potential difference

22
Q

what are three uses of a potential divider

A

to supply a pd which is fixed at any valuse between zero and the source pd
to supply a variable pd
to supply a pd that varies which a physical condition such as pressure or temperature

23
Q

what is the ratio of pds across resistors in a potential divider equal to

A

the ratio of pds across each resistor is equal to the resistance ratio of the two resistors

24
Q

what is the pd across components in parallel like?

A

the pd across components in parallel is the same

25
what the total pd across components in series equal to
the total pd across components in series is equal to the sum of the individual pds of the components