Electricity P3

Question 1

What is charging by friction?

Answer 1

when certain insulating materials are rubbed together they become electrically charged

Question 2

give an example of electric charge

Answer 2

a plastic rod being charged by rubbing it with a cloth, both insulators

Question 3

explain the movement of electrons

Answer 3

negatively charged electrons move from one material to another. the material which lost the negative electrons become positively charged and the material which gained the electrons becomes negatively charged.

Question 4

what force is exerted when two charged particles/objects are close together?

Answer 4

attraction/repulsion

Question 5

what is electric current?

Answer 5

the rate of flow charge

Question 6

why are wires in an electric circuit made of metal?

Answer 6

because metals are good conductors of electric current

Question 7

what is used to measure current?

Answer 7

ammeter

Question 8

calculation for current?

Answer 8

current = charge/time

Question 9

examples of sources of potential difference (voltage)

Answer 9

1 a cell
2 batteries
3 electrical generator

Question 10

what does conventional current mean?

Answer 10

the amount of current flowing into the junction is equal to the total amount flowing out

Question 11

what is the direction of current flow?

Answer 11

positive to the negative terminal of the power supply

Question 12

what is potential difference measured in and how is it set up?

Answer 12

using a voltmeter in parallel

Question 13

how to increase the resistance of a circuit?

Answer 13

add resistors or variable resistors

Question 14

how is resistance and current related?

Answer 14

they are opposite. high resistance means low current, vice versa

Question 15

what is the equation that links current, resistance, and potential difference?

Answer 15

potential difference = current x resistance

Question 16

what are the two types of resistors?

Answer 16

variable resistor and fixed resistor

Question 17

what is a thermistor?

Answer 17

a temperature-dependent resistor

Question 18

explain the relationship between resistance and thermistors

Answer 18

low temperature means high resistance, vice versa

Question 19

what are LDRs

Answer 19

light sensors that are useful in circuits eg automatically turning lights on. less light higher resistance, vice versa

Question 20

what is Ohm’s law?

Answer 20

as the voltage across a component increases the current also increases

Question 21

what does it mean if an I-V graph is linear?

Answer 21

the graph is a straight line, if it goes through the origin it’s directly proportional. obeys Ohm’s law

Question 22

explain the characteristics of a filament lamp

Answer 22

current and potential difference are inversely proportional

Question 23

why do diodes only allow current to flow in one direction?

Answer 23

diodes have high resistance so no current flows in the reverse direction - reverse bias

Question 24

what is the independent variable in circuit diagrams?

Answer 24

potential difference (V)

Question 25

what is the dependent variable in circuit diagrams?

Answer 25

current

Question 26

what are the control variables in circuit diagrams?

Answer 26

1 potential difference of the power supply 2 use of the same equipment e.g diode

Question 27

explain the experiment for I-V characteristics.

Answer 27

1 set up the circuit with the fixed resistor 2 change the resistance of the variable resistor to vary the voltage across the component 3 calculate average current from the ammeter after doing it three times 4 increase voltage 5 circuit cooling 6 negative voltage 7 replace fixed resistor with filament lamp then diode and repeat experiment

Question 28

state the characteristics of a series circuit

Answer 28

1 one loop 2 potential difference is shared 3 if one component breaks, circuit stops working

Question 29

state the characteristics of a parallel circuit

Answer 29

1 two loops 2 components are individually controlled 3 can function if a component breaks 4 the current splits up

Question 30

how to calculate resistance in series circuits

Answer 30

add up all the resistors

Question 31

what happens when more resistors are added in parallel

Answer 31

total resistance decreases

Question 32

steps for an LDR circuit

Answer 32

1 dark room 2 record readings using voltmeter & ammeter 3 increase light intensity slowly

Question 33

calculation for electrical power

Answer 33

power(w) = current x potential difference

Question 34

what is the calculation of power in terms of resistance

Answer 34

p = i^2r or p = v^2/r

Question 35

calculation for energy transfers

Answer 35

energy = power x time

Question 36

since p=iv what's another equation for energy transfer

Answer 36

e = I x V x T

Question 37

Equation that links energy, voltage and charge?

Answer 37

E = Q x V