electricity

Question 1

charge

Answer 1

current x time

Question 2

difference between alternating current and direct current

Answer 2

alternating current - continuously changes direction e,g main electricity

direct current - current flows in 1 direction only e.g cells, battery

Question 3

conventional current

Answer 3

flowing from positive to negative

Question 4

potential difference

Answer 4

voltage

Question 5

resistance

Answer 5

r = voltage / current
increased resistance = reduces the current

Question 6

resistance facts

Answer 6

resistance is directly proportional to length of wire
resistance is inversely proportional to diameter of wire

Question 7

power

Answer 7

voltage x current

Question 8

energy transferred

Answer 8

voltage x current x time

Question 9

voltage

Answer 9

current x resistance

Question 10

work done

Answer 10

voltage x charge

Question 11

units used

Answer 11

power x time

Question 12

in a series circuit

Answer 12

current is the same everywhere

voltage of individual components adds up to the total voltage

total resistance is the sum off all the individual components’ resistance

Question 13

in a parallel circuit

Answer 13

voltage is the same everywhere

current of individual components adds up to the total current

combined resistance of two resistors in parallel is less than that of either resistor by itself

Question 14

what is variable potential divider

Answer 14

uses a variable resistor to take portion of cells voltage

to be delivered to a separate circuit - amount of voltage delivered can be altered by varying the resistors

Question 15

equation for two resistors used as a potential divider

Answer 15

r1/r2 = v1/v2

Question 16

rectifier

Answer 16

a component used to change an alternating current into a direct current

Question 17

diode

Answer 17

allow current to flow in 1 direction and used to produce a direct current from an alternating current

Question 18

LDR

Answer 18

as light intensity increases, resistance decreases

used in circuits as an input transducer

when placed in potential divider to deliver voltage to a lamp , the lamp will come on when its dark.

Question 19

Thermistors

Answer 19

resistance decreases as temperature increases

• used as input transducer in circuits needed to be sensitive to temperature e.g fire alarms
• thermistor is placed in a potential divider to deliver high potential difference in high temperature
• attached to a relay high voltage is used to turn on an electromagnet

Question 20

increase the size of the induced current

Answer 20

1. stronger magnets
2. stronger magnetic field
3. move wire faster
4. wrap wire into a coil

Question 21

electromagnetic induction

Answer 21

if a wire is moved into a magnetic field at right angles, voltage is induced
and if connected up to a complete circuit
- current is induced

Question 22

what dictates the direction of the induced emf

Answer 22

it opposes the charge causing it

• e.g bar magnet approaches wire carrying a current which has turned into a temporary magnet
• this temporary magnet repels bar magnet approaching