p3 - electricity (from textbook)

Question 1

what happens when you rub two insulators together?

Answer 1

you can transfer electrons from one insulator to the other

Question 2

describe how to discharge an object

Answer 2

connect it to something that allows the charges to flow e.g. cobalt

Question 3

define current

Answer 3

the rate of flow of charged particles, or charge

Question 4

define conventional current

Answer 4

positive to negative flowing current

Question 5

what is conventional current the opposite of?

Answer 5

electron flow

Question 6

define potential difference

Answer 6

the difference of electrical potential between two points

Question 7

describe a series circuit

Answer 7

a circuit with only one loop

Question 8

describe a parallel circuit

Answer 8

a circuit with 2 or more loops

Question 9

describe current in a parallel circuit

Answer 9

it adds up

Question 10

describe the resistance in a parallel circuit

Answer 10

always smaller than the smallest resistor

Question 11

describe the resistance in a series circuit

Answer 11

it adds up

Question 12

describe how resistance is produced

Answer 12

when delocalised electrons collide with other ions in the lattice

Question 13

define a characteristic graph

Answer 13

a graph of current against potential difference

Question 14

describe ohm’s law

Answer 14

the current is proportional to the p.d if the temperature does not change

Question 15

name and describe an example of a non-linear circuit element

Answer 15

a wire in a light bulb - electrons collide with ions, but as the wire heats up, they move faster and more collisions happen - current increases at a slower rate compared to the potential difference

Question 16

describe a diode

Answer 16

a component that only allows a current to flow one way

Question 17

describe the characteristic graph of a diode

Answer 17

0 current for ages, then the current suddenly increases

Question 18

describe a thermistor

Answer 18

a component made from a semiconducting material, where its resistance depends on temperature

Question 19

describe the most important characteristic of a semiconductor (according to physicists)

Answer 19

electrons in the atoms of a semiconductor do not need much energy to escape from the atom to form the current

Question 20

describe how a thermistor works

Answer 20

as you heat it up, electrons gain the energy to escape from atoms in the semiconductor

Question 21

describe the main characteristic of a LDR and how it works

Answer 21

its resistance changes with light intensity - light cause electrons to be released into the circuit to increase the current

Question 22

name and describe a potential use for a thermistor

Answer 22

could be used in a sensing circuit to produce a potential difference that changes with temperature - could use it in a heater or air conditioning

Question 23

describe the difference between a cell and a battery

Answer 23

a cell is a single unit that produces electricity, whereas a battery is a group of cells connected in series and/or parallel