electricity

Question 1

what is emf

Answer 1

the total work done by a cell per coloumb of charge

Question 2

what is ohm’s law

Answer 2

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

Question 3

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

Answer 3

The potential difference

Question 4

what is the terminal potential difference

Answer 4

the voltage across the terminals of a battery

Question 5

what can internal resistance be thought of as

Answer 5

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

Question 6

how is resitance related to length

Answer 6

resistance is proportional to length

Question 7

how is resistance related to area

Answer 7

resistance is inversly proportional to area

Question 8

what is the relationship between a thermistor and increasing temperature

Answer 8

the resistance of the thermistor decreases

Question 9

what is the relationship of an LDR and increasing light intensity

Answer 9

the resistance of the LDR increases

Question 10

how would you measure the emf of a battery/cell

Answer 10

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

Question 11

why must a voltemeter have very high resistance

Answer 11

so there is virtually no current

Question 12

what is resistance

Answer 12

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

Question 13

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

Answer 13

it’s resistance increases when it’s temperature increases

Question 14

what is a superconductor

Answer 14

a material with zero resistivity at or below critical temperature

Question 15

what is the temperature coefficient of a semi-conductor

Answer 15

negative temperature coefficient resistance decreases with increasing temperature

Question 16

what is the current law at junctions

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

the differences between the cells

Question 20

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

Answer 20

the sum of the invdividual emfs of the cells

Question 21

what is a potential divider

Answer 21

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

with a source of fixed potential difference

Question 22

what are three uses of a potential divider

Answer 22

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

Question 23

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

Answer 23

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

Question 24

what is the pd across components in parallel like?

Answer 24

the pd across components in parallel is the same

Question 25

what the total pd across components in series equal to

Answer 25

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