Electricity

Question 1

what is current

Answer 1

the rate of flow of charge

Question 2

what is potential difference

Answer 2

the work done per unit charge between 2 points

Question 3

what is 1 coulomb

Answer 3

the amount of charge that passes in 1 second when the current is 1

Question 4

what type of circuit must the ammeter be attached to get a current reading

Answer 4

An ammeter must always be attached in series

Question 5

what type of circuit must a voltmeter be attached to get a voltage reading

Answer 5

It must be attached in parallel

Question 6

what is potential difference between 2 points

Answer 6

The amount of work done moving charge between those points

Question 7

what is resistance

Answer 7

How difficult it is for current to pass through

Question 8

What is ohms law

Answer 8

current is directly proportional to the voltage across it

Question 9

what are ohmic conductors

Answer 9

conductors that follow ohms law

Question 10

When does Ohms law become true for components

Answer 10

When constant physical factors such as temperature and light remain constant

Question 11

what does an I-V graph of an ohmic conductor look like

Answer 11

straight line graph going through the origin

Question 12

what does a lower gradient of a I-V graph mean

Answer 12

there is a greater resitscance

Question 13

what is a rheostat

Answer 13

a variable resistor used to control current

Question 14

what is the resistance of a voltmeter

Answer 14

infinite resistance

Question 15

what is the resistance of an ammeter

Answer 15

0/no resistance

Question 16

how does heat effect resistance

Answer 16

the particles vibrate more at higher temperatures which makes it harder for electrons to move through the wire

Question 17

What are diodes

Answer 17

Semi-conductors that only let current flow in one direction

Question 18

What is forward

Answer 18

The direction in which current is allowed to flow

Question 19

What is the threshold voltage i

Answer 19

The voltage required for diodes to allow current to flow. (It is normally 0.6V)

Question 20

Is a filament lamp an ohmic conductor

Answer 20

No it isnt

Question 21

How can you tell what is or is not an ohmic conductor

Answer 21

The I-V graph needs to be a straight line. If the graph is not a straight line then it is not an ohmic conductor

Question 22

what is resistivity

Answer 22

It is a measure how much a particular material resists current flow

Question 23

what is the difference between resistance and resistivity

Answer 23

Resistivity is how much a MATERIAL resists current flow whilst
Resistance is how much an OBJECT resists current.

resistivity is a property of a material while resistance is the property of an object.

Question 24

What is a semi-conductor

Answer 24

It is a material that doesnt conduct electricity as good as metals because they have fewer electrons

Question 25

what are 3 common semi-conductor

Answer 25

-thermistor -diode -LDR`

Question 26

what is a thermistor

Answer 26

It is a component where is the temperature is higher the resistance is lower. This is because higher temperature means more electrons escape from their atoms so there will be more charge carriers

Question 27

what is a LDR

Answer 27

It is a light dependent resistor which means the more light the lower the resistance.

Question 28

What is a superconductor

Answer 28

A conductor which has 0 resistance

Question 29

How can you make a super conductor

Answer 29

- By reducing the temperature you can lower the resistance till eventually you get 0 resistance

Question 30

what is traditional temperature

Answer 30

It is the critical temperature that needs to make a superconductor.

Question 31

What are 2 uses of a superconductor

Answer 31

- power cables - creating a strong magnet for medicinal uses

Question 32

what is power

Answer 32

The rate of energy transfer

Question 33

What is the equation for energy transfer without using power

Answer 33

E = IVt energy transfer = current x voltage x time

Question 34

What is internal resistance

Answer 34

The resistance inside of a battery

Question 35

What is e.m.f

Answer 35

It it the energy transferred to each electron. e.m.f is measured in volts

Question 36

What is load resistance

Answer 36

The total external resistance in a circuit (this does not include internal resistance)

Question 37

What is terminal p.d

Answer 37

The energy transferred when one coulomb of charge flows through the load resistance

Question 38

what is lost volts

Answer 38

The energy lost in overcoming the internal resistance

Question 39

what is the equation for e.m.f with lost volts

Answer 39

e.m.f = lost volts+ terminal p.d

Question 40

what is kirchoffs first law

Answer 40

current entering a junction is equal to current leaving a circuit

Question 41

what is kirchoffs second law

Answer 41

the total e.m.f is equal to all the p.d of all the components

Question 42

how do you calculate the total e.m.f of cells in series

Answer 42

You add the e.m.f of all the cells together

Question 43

how do you calculate the total e.m.f of all cells in parallel

Answer 43

The total e.m.f is the same as the e.m.f of one cell

Question 44

what are potential divider circuits

Answer 44

circuits which produce an output voltage as a fraction of their input coltage

Question 45

what are the 3 main reasons for using a potential divider

Answer 45

- to produce a varying potential difference - to be able to choose a specific potential difference - to split the potential difference between two components

Question 46

what is the equation for a potential divider

Answer 46

Vout = (R2/(R1+R2))Vin

Question 47

what happens when you switch a fixed resistor with a variable resistor like a thermistor

Answer 47

the output voltage will vary