electricity

Question 1

what happens to the current as the resistance gets greater?

Answer 1

the current is smaller

Question 2

how can you investigate the effect of a wire length on the resistance?

Answer 2

attach a crocodile clip to wire with 0cm on ruler
attach second crocodile clip to wire and write down length
close switch and record current and pd
open switch and move croc clip, close switch again and record new length, current and pd
repeat
use measurements to calculate the resistance
plot a graph

Question 3

what happens to the resistance of ohmic conductors?

Answer 3

doesn’t change with the current, constant temp, current is directly proportional

Question 4

features of a light dependent resistor?

Answer 4

in bright light the resistance falls
in darkness the resistance is highest
automatic night lights, burglar detectors

Question 5

features of Thermistor?

Answer 5

hot conditions- resistance drops
cool conditions resistance goes up
temperature detector, car engine, thermostats

Question 6

whats alternating current?

Answer 6

current constantly changing direction, produced by alternating voltages

Question 7

what is the brown wire?

Answer 7

live wire, alternating pd from mains

Question 8

what is the blue wire?

Answer 8

completes a circuit, current flows through live and neutral at 0v

Question 9

what is the green and yellow wire?

Answer 9

earth wire, safety, stops appliance casing becoming live, doesn’t carry current, 0v

Question 10

what does the power rating tell you?

Answer 10

maximum amount of energy transferred between stores per second when the appliance is in use

Question 11

what does increasing the potential difference do to the current?

Answer 11

decreases the current

Question 12

what do transformers consist of?

Answer 12

2 coils (primary and secondary)
joined with an iron core

Question 13

whats static electricity?

Answer 13

charges which are not free to move e.g insulating materials, spark and shock when finally move

Question 14

what happens when certain insulating materials are rubbed together?

Answer 14

negatively charged electrons will be scraped off one and dumped on the other, leaving material electrically charged with positive static charge on one and an equal negative on the other

Question 15

How are sparks formed?

Answer 15

electric charge building up on an object, pd between object and earth increases, when pd is large enough electrons can jump across the gap, can jump to any earthed conductor

Question 16

features of electric field lines?

Answer 16

go from positive to negative, always at a right angle to surface, closer together the lines are the stronger the field is

Question 17

features of electric field lines?

Answer 17

go from positive to negative, always at a right angle to surface, closer together the lines are the stronger the field is

Question 18

How can sparking be explained by electric fields?

Answer 18

high enough pd between charged object and earth
causes a strong electrical field between charged object and earthed object
causes electrons to be removed in air particles (ionisation)
current can now flow through air causing a spark