electricity

Question 1

what is energy

Answer 1

work done by a force of one newton when it moves one metre in the direction of action of the force

Question 2

what is frequency

Answer 2

one oscillation per second

Question 3

what is current

Answer 3

when 1 coulomb of charge flow past a point in one second

Question 4

what is potential difference

Answer 4

when 1 joule of energy is transferred to ( or form ) 1 coulomb of charge

Question 5

what is power

Answer 5

when 1 joule of energy is transferred in 1 second

Question 6

what is charge

Answer 6

1 coulomb is the amount of charge delivered by 1 ampere of current in 1 second

Question 7

what is resistance

Answer 7

transmits a current of one ampere when subjected to a potential difference of 1 volt

Question 8

what is resistivity

Answer 8

resistance of unit length of wire with unit cross sectional area

Question 9

what is the voltage called that starts a diode and what is the the voltage

Answer 9

trigger voltage 0.7v

Question 10

what does a diode on a graph look like

Answer 10

follows the line of the x axis until the trigger voltage which causes a gradual gradient

Question 11

what is Kirchhoff’s first law

Answer 11

total current into a junction = total current out of a junction

Question 12

what is EMF

Answer 12

electromotive force

Question 13

how many electrons are required to carry 1 coulomb of charge

Answer 13

no. of electrons = 1C/1.6x10^-19C = 6.25x10^18

Question 14

what is the equation for volts

Answer 14

energy transferred / charge

Question 15

what are the 2 types of circuits

Answer 15

-series
-parallel

Question 16

list 12 electrical components

Answer 16

-switch
-cell
-lamp/bulb
-resistor
-variable resistor
-LDR
-thermistor
-diode
-LED
-ammeter
-voltmeter
-fuse

Question 17

what is the equation for resistance in a series circuit

Answer 17

Rt = R1 + R2… + Rn

Question 18

what is the equation for resistance in a parallel circuit

Answer 18

1/Rt = 1/R1 + 1/R2… + 1/Rn ( inverse)

Question 19

what is electrical current

Answer 19

electrical current is the rate of flow of charge.

Question 20

what is the equation for electrical current`

Answer 20

I = ΔQ/Δt

Question 21

what is the rearranged equation for amps

Answer 21

ΔQ = IΔt

Question 22

how does resistance correlate with resistivity

Answer 22

they are directly proportional

Question 23

how does resistance correlate with with length

Answer 23

they are directly proportional

Question 24

how does resistance correlate with with the cross sectional area of the wire

Answer 24

they are inversely proportional

Question 25

what is the equation for resistivity

Answer 25

Ρ = RA/l (resistivity = resistance*area / length)

Question 26

what is the equation for resistance using resistivity

Answer 26

R = ρl/a ( resistance = resistivity*length/area)

Question 27

define resistivity

Answer 27

resistance is a constant material property, whereas resistance is a sample/specific, depending on a materials resistivity, length and cross sectional area.

Question 28

how do thermistors work

Answer 28

an increase in temperature causes an increase in resistance and vice versa, so the resistance varies with temperature

Question 29

most thermistors are negative temperature coefficient what does this mean

Answer 29

this means if the temperature increases the resistance of the thermistor decreases and vice versa

Question 30

describe resistance in terms of particles

Answer 30

the electrons collide with the vibrating atoms which impede their flow, so the current decreases

Question 31

doubling the length of the wire will

Answer 31

will double the resistance

Question 32

doubling the cross sectional area of a wire will

Answer 32

half the resistance

Question 33

what is conventional current flow

Answer 33

Flow from positive to negative, used to describe the direction of current in a circuit.

Question 34

what does a diode do

Answer 34

Components that allow current through in one direction. In the correct direction, diodes have a threshold voltage (typically 0.6 V) after which current flows normally.

Question 35

what is the EMF (electromotive force)

Answer 35

The energy supplied by a source per unit charge passing through the source, measured in volts

Question 36

what is internal resistance

Answer 36

The unavoidable resistance any power source will have that makes it harder for current to flow through the source. It causes energy to be dissipated in the source.

Question 37

describe how a potential divider works (3-4 marks)

Answer 37

-combination of two or more resistors in series. -These result in the potential difference of the circuit being split into a specific ratio depending on the resistance of the resistors. -They can be used to get a specific output voltage from the circuit.