electricity

Question 1

what is electric current

Answer 1

it is the flow of electrons from the NEGATIVE tot he POSITIVE end of a cell

Question 2

what is current

Answer 2

it is the flow of electrical charge around a circuit and is measures in amperes and can be measures using ammeters

Question 3

what is the conventional current

Answer 3

it is the idea that electrons flow from the positive end of a cell to the n negative end

Question 4

how is current distributed in a series circuit

Answer 4

current can never be used up meaning that it will be the same around the whole circuit

Question 5

how is current distributed in a parallel circuit

Answer 5

the total current of each branch is equal to the total current flowing

Question 6

what is potential difference

Answer 6

one volt is one joule of energy is transferred for each coulomb of charge
it is the difference in the amount of energy between two points in a circuit

Question 7

what happens to potential difference in a series circuit

Answer 7

the total potential difference in the circuit is equal to the potential difference of the cell

Question 8

what happens to the potential difference in a parallel circuit

Answer 8

the voltage across each branch is te same as the cells

Question 9

what is the charge flow in a circuit

Answer 9

it is measured in coulombs and one ampere is one coulomb flowing per seconds. the size of the current is the rate of flow of electrical charge

Question 10

what is the formula for charge flow

Answer 10

it is charge flow (coulombs) = current (A) * time (seconds)

Question 11

what is the formula for energy transferred

Answer 11

energy transferred (J) = charge flow C (coulombs) * potential difference (V)

Question 12

what is the formula for energy transferred

Answer 12

energy transferred (J) = charge flow (C coulombs) * potential difference (V)

Question 13

what is resistance

Answer 13

it is the potential difference required to drive a current through an electrical component
or how easily an object resists current

Question 14

what is the formula for voltage

Answer 14

V = I * R or voltage = current * resistance

Question 15

what does a current -voltage graph look like for an ohmic component

Answer 15

a directly proportional graph with a straight line

Question 16

what is an ohmic component

Answer 16

a component that does not change its resistance as you increase the current. However the resistance will only stay constant at a constant temperature

Question 17

what does the current voltage graph look like for a non ohmic component

Answer 17

it is not directly proportional and gets flatter as the component gets hotter

Question 17

what does the current voltage graph look like for a non ohmic component

Answer 17

it is not directly proportional and gets flatter as the component gets hotter

Question 18

why does the resistance increase at high temperatures

Answer 18

at high temperatures the atoms vibrate more causing the electrons in the current to collide more meaning more energy is needed to push the current

Question 19

what is a diode

Answer 19

a compontent that has very little resistance in the forwards direction but high resistance in the backwards direction

Question 20

what happens to the resistance in a series circuit

Answer 20

the total resistance is the resistance of all components and resistors added together

Question 21

what happens to the resistance in a parallel circuit

Answer 21

the total resistance is smaller than the smallest resistor

Question 22

what does a current to voltage graph look like for a resistor

Answer 22

it is directly proportional

Question 23

what happens to the resistance of an LDR when light changes

Answer 23

as light increases the resistance decreases and as the light levels decrease the resistance increases

Question 24

what happens to the resistance of the thermistor as the temperature changes

Answer 24

at low temperatures it has a very high resistance and at high temperatures it has low resistance

Question 25

how to measure resistance against the length of a wire

Answer 25

use a circuit that measures voltage and current and the use crocodile clips on a piece of wire attached to a ruler to adjust the length

Question 26

what is the relation of resistance to the length of the wire

Answer 26

they are directly proportional

Question 27

what is zero error and how can it be accounted for

Answer 27

zero error is a reading on a measuring instrument when the value should be zero and this is a systematic error which cannot be solved by doing repeats. In order to account for this we need to subtract this value from all of our readings.

Question 28

how can we improve the test to see the affect of altering resistance on a circuit

Answer 28

use a variable resistor or a piece of coiled wire that has a slider that changes its resistance

Question 29

what is the power rating of an appliance

Answer 29

it is the amount of energy transferred every second

Question 30

what usually has a higher power rating thermal energy appliances of kinetic

Answer 30

thermal energy

Question 31

what is the formula for energy

Answer 31

energy (J) = power (W) * time (s)

Question 32

what is the formula for power

Answer 32

Power (W) = current (A) * voltage (V)

Question 33

what is the formula for power

Answer 33

Power (W) = current squared (A) * resistance

Question 34

what is DC voltage

Answer 34

it is the current from a cell that only moves in one direction

Question 35

what is AC voltage

Answer 35

it is when the current is constantly changing direction

Question 36

what is the benefit of alternating current

Answer 36

it is very easy to use a transformer to increase or decrease the potential difference

Question 37

what is the frequency of the main UK electricity

Answer 37

it is 50 hertz or switches direction to complete one cycle 50 times a second

Question 38

how many volts is the mains UK electricity

Answer 38

around 230 V

Question 39

what is the function of the live wire

Answer 39

the live wire is the brown wire and carries the alternating potential difference from the supply (230V). The live wire is connected to a fuse in the plug

Question 40

what is the function of the neutral wire

Answer 40

the neutral wire is the blue one and completes the circuit

Question 41

what is the function of the earth wire

Answer 41

the green and yellow striped earth wire acts a safety wire to stop the appliance becoming live. If the appliances metal case becomes live electricity flows into the earth wire which is connected to the ground which offsets a huge current to the earth melting the fuse

Question 42

what is the national grid

Answer 42

it contains high voltage cables and transformers and transfers energy across the UK

Question 43

what do step up transformers do

Answer 43

they increase the voltage to several thousand volts as less energy is lost when it has a high voltage