Current Electricty

Question 1

What is the equation linking energy current and time and voltage

Answer 1

Energy = current x voltage x time

Question 2

What is the equation linking energy charge and voltage

Answer 2

Energy = charge x voltage

Question 3

What is the equation linking charge current and time

Answer 3

Charge = current x time

Question 4

What is resistance

Answer 4

Voltage over current

Question 5

What is energy measured in

Answer 5

Joules

Question 6

What direction does current flow

Answer 6

Positive to negative

Question 7

What happens in a parallel circuit

Answer 7

Cell runs down more quickly
Voltage across each branch is the same as the supply
Current in branches equal that of supply

Question 8

What happens in series circuit

Answer 8

Voltage across the circuit = supply

Current is the same everywhere

Question 9

What is a straight line graph show

Answer 9

Directly proportional

Question 10

Why does resistance increase with voltage and current

Answer 10

Lamp Gets hotter so it’s harder for the current to get through this increases resistance as the particles vibrate more and it’s harder for the electrons to flow through

Question 11

What is an ldr

Answer 11

Light dependent resistor that resistance depends on the intensity of light falling on it an example is automatic street lamps

Question 12

What is mains electricity

Answer 12

230 volts

Question 13

What is a thermistor

Answer 13

Temperature dependent resistor as temperature increases resistance decreased

Question 14

Example of thermistor

Answer 14

In fridges when the fridge gets to hot the thermistor will activate the circuit

Question 15

What is a diode

Answer 15

Allows current to flow in one way only . If diode is connected wrong way no current will flow

Question 16

How do u activate diode

Answer 16

Voltage of 0.7 v must bbe applied to the diode

Question 17

What is a rhetostat

Answer 17

Type of variable resistor . Long coil of resistance wire with a sliding contact .

Question 18

What happens as you bring in more cool on the rhetostat

Answer 18

More coil increases resistance and current goes down

Question 19

What is a series circuit

Answer 19

Single loop with only one path for charges to flow

Question 20

What is a parallel circuit

Answer 20

Junctions so there is more than one path for current to flow

Question 21

Why do bulbs glow brighter in parallel

Answer 21

Parallel as voltage is the same everywhere

Question 22

What has a modern household circuit got

Answer 22

Lighting circuit

Main power circuit

Question 23

What are the modern house hold circuits protected by

Answer 23

Lighting - 5 amp fuse
Power circuit - 30 amp fuse
Each power point in the house is protected by a fuse

Question 24

What is the live wire

Answer 24

Comes from power station and is the most dangerous as mains voltage can easily kill you

Question 25

What is the neural wire

Answer 25

Completes the circuit comes from power station and is earthed back to power station so does not carry as much voltage as the live wire

Question 26

What is the earth wire

Answer 26

For safety , only carries current when there is a fault so that a fuse melts

Question 27

How is the current supplied in your house

Answer 27

Alternating current - current flows one way and then the opposite way , 50 times each way each second

Question 28

What do fuses do

Answer 28

Melt if current is too high and stop current flow before anything else is damaged or a fire is started

Question 29

What must you do if a fuse melts

Answer 29

Switch off the circuit Find reason for the fault Replace fuse

Question 30

When is the earth wire used

Answer 30

If a fault develops in an appliance and the live wire touches the metal case a large current flows from live wire to earth wire and the fuse breaks

Question 31

Where must the fuse be placed

Answer 31

In the live wire so it can isolate the appliance from the live wire

Question 32

What does double insulated mean

Answer 32

Doesn't need an earth wire as it has an insulating plastic case so no risk of electric shock if the live wire touches casing

Question 33

Why r circuit breakers better than fuses

Answer 33

Acts more quickly more reliable and can be reset

Question 34

What is direct supply

Answer 34

From cell or battery of cells and has direct current meaning current only flows in one direction from positive to negative

Question 35

How do circuit breakers work

Answer 35

A switch opens if too large a current flows and causes the circuit to be incomplete . Once the fault has been corrected the switch is reset by pressing a reset button and does not have to be replaced

Question 36

What does the earth wire provide

Answer 36

Los resistance path for current to flow

Question 37

Where should switches be in mains electricity

Answer 37

In the live wire so when the switch is open no electrical energy can reach the appliance if the witch was in the neutral wire electrical energy would still be able to reach the appliance and possible cause electric shock

Question 38

Dangers of mains electricity

Answer 38

Too many plugs in one socket can cause overheating of cables and fire. Overhrating can also occur from long coiled cables Water near sockets / switches Frayed cables / damaged insulation

Question 39

What happens to components in parralel

Answer 39

Can be switched on and off independently

Question 40

What are the 4 equations

Answer 40

Charge = current x time Energy = charge x voltage Resistance = voltage over current Electrical power = current x voltage

Question 41

Why is the outer plug made of plastic

Answer 41

Good insulator so no electric shock

Question 42

Why are connections in mains made of brass

Answer 42

Good conductor

Question 43

Why are frayed wires bad

Answer 43

Exposes metal carrying electricity could cause electric shock

Question 44

What is the purpose of the cable grip

Answer 44

Stops the cable and wires from being pulled out the plug

Question 45

Alternating current

Answer 45

Current which constantly changes direction