electric circuits

Question 1

current

Answer 1

rate of flow of charge, Q/t

Question 2

potential difference

Answer 2

energy transferred per unit charge W/Q

Question 3

resistance

Answer 3

measure of how difficult it is for charge carriers to pass through a component, V/I

Question 4

conservation of charge

Answer 4

total charge in a circuit does not change

Question 5

kirchoffs first law

Answer 5

current flowing into a junction is equal to the current flowing out

Question 6

current in series and parallel

Answer 6

series- current is the same everywhere
parallel- sum of current in parallel branches is equal to total current

Question 7

energy conservation

Answer 7

energy cannot be created or destroyed, only transferred

Question 8

kirchoffs second law

Answer 8

sum of voltages in a series circuit =0

Question 9

voltage in series and parallel

Answer 9

series- total sum of the voltages of components is equal to supply p.d
parallel- potential difference across each bench is divided

Question 10

combining resistance in series

Answer 10

Rt=R1+R2+R3…
Vt=V1+V2+V3..
Vt=IR1+IR2+IR3..

Question 11

combining resistance in parallel

Answer 11

1/Rt=1/R1+1/R2+1/R3…
It=I1+I2+I3…
It=V/R1+V/R2+V/R3…

Question 12

equations involving power

Answer 12

P=VI
W=Pt
W=VIt

Question 13

ohmic conductor

Answer 13

follows ohms law, V and I are directly proportional

Question 14

Semi conducting diode

Answer 14

allows current to flow in one direction once past its threshold voltage

Question 15

filament bulb

Answer 15

heats up as current increases which increases resistance, follows ohms law at low currents

Question 16

thermistor

Answer 16

as it heats up resistance falls as charge carriers are freed

Question 17

resistivity

Answer 17

measure of how easily a material conducts electricity

Question 18

determining factors of current

Answer 18

-number of charged particles
-speed at which particles travel at
-charge of the particles
I=nqvA

Question 19

how does resistance vary with length

Answer 19

p.d and resistance both increase with length

Question 20

potential divider circuits

Answer 20

circuit with several resistors in series connected across a voltage source, used to produce a required fraction of the source p.d, which remains constant

Question 21

emf & internal resistance

Answer 21

batteries have internal resistance which is caused by electrons colliding with the atoms in the battery, causing electrons to be lost.

Question 22

change in resistance with temperatures in metallic conductors

Answer 22

atoms in most solids have a crystal lattice structure. as temp increases, the intensity of the atoms vibrations increases. the more intense the vibrations, the harder it is for electrons to pass through, as they are more likely to collide with atoms

Question 23

change in resistance with temperatures in negative temperature coefficient thermistors

Answer 23

as temperature increases, its atoms gain energy and once they gain enough energy they begin to release electrons. this increases the number of charge carriers and therefore decreases resistance

Question 24

changes in resistance with light intensity

Answer 24

LDRs are made out of photoconductive material (release electrons in the presence of light). as light intensity increases, electrons are released which increases the number of charge carriers, so resistance falls

Question 25

in which direction does current flow in a circuit

Answer 25

from the positive terminal to the negative