current and circuits

Question 1

what is current and unit

Answer 1

flow of electric charge (electrons) around a circuit
unit - amp (a)

Question 2

what is potential difference (pd) and unit

Answer 2

pd is energy transferred per unit charge
unit - volt (v)

Question 3

what is resistance and unit

Answer 3

anything which slows down flow
unit - ohm

Question 4

charge equation

Answer 4

current x time

Question 5

name all the circuit symbols

Answer 5

• cell
• battery
• open switch
• closed switch
• filament lamp
• fuse
• LED
• power supply
• resistor
• variable resistor
• ammeter
• voltmeter
• diode
• LDR
• thermistor
• motor

Question 6

energy transferred equation

Answer 6

charge moved x potential difference

Question 7

what usually happens to resistors and why

Answer 7

increase with temperature as a charge flows through as it has to do work against the resistor. this is due to electrons colliding and vibrating which heat up.

Question 8

what is an ammeter

Answer 8

measures current flowing anywhere in the circuit

Question 9

what is a voltmeter

Answer 9

measures potential difference across a component

Question 10

how to investigate diodes

Answer 10

remove diode and swap its direction, current can no longer flow through

Question 11

how to investigate thermistors

Answer 11

gradually heat it while keeping pd the same, temp should increase as resistance increases

Question 12

how to investigate LDRS

Answer 12

in a dim room, keep pd the same and slowly adjust light level near the LDR. light level should get brighter, current increases and resistance decreases.

Question 13

resistor and wires graph

Answer 13

current is directly proportional to pd, all different slopes

Question 14

filament lamp graph

Answer 14

increasing current increases temp, graph is curved

Question 15

diode graph

Answer 15

current only flows one direction, high resistance in opposite direction

Question 16

series circuit

Answer 16

different components are all connect end to end

Question 17

parallel circuit

Answer 17

every component is connected separately -parts don’t effect each other.

Question 18

energy transferred equation

Answer 18

current x pd x time

Question 19

things which reduce efficiency

Answer 19

• melts (heat energy, pointless)
• fuses

Question 20

electric power equation

Answer 20

current x pd

Question 21

3 types of wire in a plug

Answer 21

• live
• earth
• neutral

Question 22

live wire facts

Answer 22

• brown
  carries voltage (230v)

Question 23

earth wire facts

Answer 23

• green and yellow
  carries current away if needed to safety incase something goes wrong and carries 0v

Question 24

neutral wire facts

Answer 24

• blue
  competes circuit and electricity flows out of it
  also carries 0v

Question 25

circuit breaker

Answer 25

turn off quickly to reduce risk of electric shock. found in households fuses