resistance/circuits/wires/electronics

Question 1

how can you calculate resistance

Answer 1

R = V
-
I

r=resistance
V=potential difference
I=Current

Question 2

why do you need to add a resistor

Answer 2

to make sure the the light isn’t too bright

Question 3

what happens to the current when you increase the potential difference on a graph

Answer 3

there is a straight line passing through 0

showing that the current through a resistor is directly proportional to the potential difference and the resistance is constant

Question 4

what must stay constant for the resistance to stay constant

Answer 4

temperature

Question 5

what is a convenstional current

Answer 5

drawing the current from the opposite direction

Question 5

what is a current

Answer 5

an electrical current is a flow of charge around a circuit

Question 6

how can you measure the potential difference

Answer 6

volt meter

Question 7

what is a ldr

Answer 7

light-dependent resistor

Question 8

what happens to the resistance in a light and dark environment to a ldr

Answer 8

in light intense areas the ldr have low resistance

in dark intense areas the ldr has high resistance

Question 8

name a way a ldr can be used

Answer 8

to turn of the screen of a mobile phone when yo are on a phone call with someone

Question 9

what does a thermistor

Answer 9

the resistance of a thermistor decreases if the temperature increases

Question 10

what happens to the resistance when the temperature is high or low

Answer 10

when the temperature is low the resistance is high

when the temperature is high the resistant is low

Question 11

where can a thermister be used

Answer 11

in a pc to turn on the fan when it heats up

Question 12

what is an alternating current

Answer 12

the flow of electrons moves forwards and in a reverse directions

Question 13

how are electrical appliances connected in the uk

Answer 13

uses a 3 core cable

Question 15

what is the blue wire

Answer 15

neutral- completes circuit potential difference = 0V
compared to the live wire

Question 16

what is the green/yellow striped wire

Answer 16

earth wire- safety wire to stop appliances from becoming live

Question 17

how does the earth wire work and what does it prevent

Answer 17

earth wire is connected to the ground if the case becomes ive a huge amount current flows to earth. The fuse melts and shuts of the current which prevents electric shocks

Question 18

why is the live wire dangerous

Answer 18

can be easily touched and still has 230 V in it and would transfer to the person and they could be electrocuted

Question 19

why can appliances with metal casing be dangerous

Answer 19

if the live wire comes loose and touches the metal case the case can come live ad have a current in it