P2

Question 1

which equation links charge flow, current and time?

Answer 1

charge flow = current x time

Question 2

which equation links p.d., current and resistance?

Answer 2

p.d. = current x resistance (IVR on triangle)

Question 3

which equation links power, energy transferred and time?

Answer 3

power = energy transferred / time

Question 4

which equation links energy transferred, charge and p.d.?

Answer 4

energy transferred = charge x p.d.

Question 5

which equation links power, p.d. and current?

Answer 5

power = p.d. x current

Question 6

which equation links power, current and resistance?

Answer 6

power = current² x resistance

Question 7

describe the live wire

Answer 7

brown
provides alternating p.d. at about 230V
from mains supply

Question 8

describe the neutral wire

Answer 8

blue
completes circuit
carries away current
0V

Question 9

how does electricity flow through the wires?

Answer 9

in through live wire

out through neutral wire

Question 10

describe the earth wire

Answer 10

green and yellow
protects wiring, for safety
stops appliance casing from becoming live
only carries current if there's a fault
0V

Question 11

what’s electric current?

Answer 11

the flow of electrical charge

size of the electric current is the rate of flow of electrical charge

Question 12

what conditions are needed for electrical charge to flow?

Answer 12

closed circuit

source of p.d.

Question 13

unit for current?

Answer 13

ampere/amps (A)

Question 14

unit for charge?

Answer 14

coulombs (C)

Question 15

unit for time?

Answer 15

seconds (s)

Question 16

definition of p.d.

Answer 16

driving force that pushes charge around (the circuit)

Question 17

definition of resistance

Answer 17

anything that slows down the flow

Question 18

definition of resistance

Answer 18

anything that slows down the flow (current)

Question 19

state the relationship between resistance and current

Answer 19

the greater the resistance across a component, the smaller the current that flows
for a given p.d. across the component

Question 20

state the relationship between current and charge

Answer 20

more charge passes around a circuit when a larger current flows

Question 21

what does the ammeter do?

Answer 21

measures current

always placed in SERIES with whatever is being measured

Question 22

what does the voltmeter do?

Answer 22

measures p.d.

always placed in PARALLEL to whatever is being measured

Question 23

what’s an ohmic conductor?

Answer 23

at a constant temp.
current flowing though it is directly proportional to the p.d. across it
(resistance stays constant as current changes)

Question 24

what happens to the R value for some resistors?

Answer 24

for some the R value stays constant

for others it can change as the current changes

Question 25

what’s an example of an ohmic conductor?

Answer 25

a resistor at a constant temp.

Question 26

for which components and resistors does the resistance not stay constant?

Answer 26

filament lamps
diodes
thermistors
LDRs

Question 27

what’s the relationship between current and resistance in non-ohmic conductors?

Answer 27

resistance changes with current through the component

Question 28

describe the trend in a filament lamp

Answer 28

when an electrical charge flows through, energy is transferred to the thermal energy store of the filament which is designed to heat up
resistance increases as the temp. of the filament increases
as current increases filament heats up more and resistance increases
less current can flow per unit p.d. so graph curves/gets shallower

Question 29

describe the trend in a diode

Answer 29

current only flows in one direction

if current is reversed there’s very high resistance

Question 30

describe the trend in an ohmic conductor

Answer 30

at a constant temp.
current is directly proportional to p.d.
so the graph has a straight line through the origin

Question 31

define the term ‘I-V Characteristics’

Answer 31

refers to a graph that shows how the current flowing through a component changes as the p.d. across it increases

Question 32

what’s a linear component?

Answer 32

have an I-V Characteristic that’s a straight line

Question 33

give an example of a linear component

Answer 33

fixed resistor

Question 34

what’s a non-linear component?

Answer 34

have curved a I-V Characteristic that’s curved

Question 35

give some examples of a non-linear component

Answer 35

filament lamp

diode