C2:Electricity

Question 1

what is p.d

Answer 1

a measure of how much energy is transferred by each coulomb of electron

Question 2

what is current

Answer 2

rate of flow of charge (how many coulombs pass every second)

Question 3

how do you calculate p.d

Answer 3

energy transferred/charge flow

Question 4

how do you calculate current

Answer 4

charge/time

Question 5

what is resistance

Answer 5

a measure of how much a component resist the flow of charge

Question 6

what is a resistor

Answer 6

heats up when current flows through it

Question 7

how are current and pd similar

Answer 7

directly proportional

Question 8

how do you calculate resistance
(ohms law)

Answer 8

p.d/current

Question 9

why does a larger current mean an increase in resistance

Answer 9

more heat means more movement of ions which causes more collisions which cause a higher resistance

Question 10

whats a diode

Answer 10

only lets a current flow in one direction

Question 11

what are the rules for a series circuit

Answer 11

total p.d is shared between components
current is the same
resistance is added together

Question 12

what are the rules for a parallel circuit

Answer 12

p.d of battery = p.d of components
current split between
total resistance is less than the resistance of the smallest resistor

Question 13

what is a thermistor

Answer 13

as temperature increases resistance decreases

Question 14

power =

Answer 14

p.d x current

Question 15

what does the neutral wire do (blue)

Answer 15

takes the current back to the source and stays ay 0v

Question 16

what does the live wire do (brown)

Answer 16

averages out the p.d to 230v
changes between positive and negative potentials

Question 17

what does the earth wire do (yellow and green)

Answer 17

safety wire which sends the current in the earth if the device becomes faulty

Question 18

what is a fuse

Answer 18

melts and reduces the current

Question 19

what do step up transformers do

Answer 19

increases voltage but decreases current to reduce the amount of power lost to heat

Question 20

what does a step down transformer do

Answer 20

reduces voltage down to a safer and useable 230v for homes

Question 21

why does resistance change for a metal

Answer 21

metals consists of a grid of ions surrounded by a sea of delocalised electron
They collide with ions and create heat
The higher the current the more frequent the collisions are which makes the ions vibrate more and makes it harder for electrons to flow
The resisitance has increased

Question 22

what happens to resistance in a diode

Answer 22

low resisitance in forward direction
high resistance in reverse direction

Question 23

whats the practical for resistance

Answer 23

metal wire with crocodile clips connected to it that has a circuit attached to it
move one clip along the wire
you should end up with a straight line through the origin
shows resistance and length of wire are directly proportional

Question 24

what is a ldr

Answer 24

light intensity increases and resistance decreases

Question 25

what does direct p.d cause (p.d that only flows in one direcion)

Answer 25

results in direct current in battery

Question 26

what types of fuses do we use

Answer 26

3a
5a
13a

Question 27

what is the national grid

Answer 27

network of power stations and net grids that transport electricity