ELECTRICITY

Question 1

2.02 how does double insulation protect the device or user in a range of domestic appliances

Answer 1

DOES NOT MEAN TWO LAYERS OF INSULATION. does not require earth connection as device is fully covered with a layer of insulation, protects user from electrocution

Question 1

2.02 how does the use of insulation protect the device or user in a range of domestic appliances

Answer 1

surrounds metal conductor with insulators, prevents user from electrocution

Question 2

2.02 how does earthing protect the device or user in a range of domestic appliances

Answer 2

gives electricity an easy path to flow, only uses the earth wire when there is a fault

Question 3

2.02 how do fuses protect the device or user in a range of domestic appliances

Answer 3

a fuse protects anything electrical from damage due to excess current. the thin wire inside the fuse melts when the current gets too high.

Question 4

2.02 how do circuit breakers protect the device or user in a range of domestic appliances

Answer 4

performs the same role as a fuse but can be reset. when the magnetic field becomes too strong, the switch is pulled open and the flow of the current is cut off.

Question 5

2.3 why does current in a resistor result in the electrical transfer in energy and an increase in temperature, how can this be used in domestic contexts?

Answer 5

Resistance causes transfer of electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens, for example electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced.

Question 6

2.5 relationship between energy transferred, current, voltage and time:

Answer 6

energy transferred= current x voltage x time

Question 7

2.4 relationship between power, current and voltage:

Answer 7

power= current x voltage

Question 8

2.6 what current is mains electricity?

Answer 8

alternating current- constantly changing magnitude and direction

Question 9

2.6 what current comes from a cell or battery?

Answer 9

direct current- constant

Question 10

2.7 advantages of a parallel circuit:

Answer 10

• Components (e.g. bulbs) may be switched on/off independently.
• If one component breaks, current can still flow through the other parts of the circuit.
• Bulbs maintain a similar brightness.

Question 11

2.7 advantages of a series circuit:

Answer 11

• Fewer wires, cheaper and easier to assemble.
• Uses less power

Question 12

2.8 what does current in a series circuit depend on?

Answer 12

• applied voltage
• number of other components- more component the lower the current
• nature of other components

Question 13

2.9 describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how to investigate this experimentally

Answer 13

• resistor= straight diagonal line
• filament lamp= s shape
• diode= flat then up
• investigate by changing the resistance of the variable resistor in a circuit

Question 14

2.10 what is the qualitative effect of changing resistance on the current in a circuit?

Answer 14

as resistance increases, current decreases

Question 15

2.11 describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature:

Answer 15

• as illumination increases, resistance decreases
• as temperature increases, resistance decreases

Question 16

2.12 what can lamps and LEDs be used for?

Answer 16

• to indicate the presence of current in a circuit

Question 17

2.13 relationship between voltage, current and resistance:

Answer 17

voltage= current x resistance

Question 18

2.14 what is current?

Answer 18

the rate of flow of charge

Question 19

2.15 relationship between charge, current and time:

Answer 19

charge= current x time

Question 20

2.16 what is electric current is solid metallic conductors?

Answer 20

flow of negatively charged electrons

Question 21

2.17 why is current conserved at a junction in a circuit:

Answer 21

At a junction current ‘splits’ to take both paths.

It comes back together when the paths meet again.

Question 22

2.18 is the voltage across two components connected in parallel the same or different?

Answer 22

the same

Question 23

2.19 calculate the currents, voltages and resistances of two resistive components connected in a series circuit:

Answer 23

VT = V1 + V2

IT = I1 = I2

RT = R1 + R2

Question 24

2.20 what is voltage?

Answer 24

• the energy transferred per unit charge passes
• voltage measures how much energy the charge flowing around the circuit has, measured in volts

Question 25

2.20 what is a volt equal to?

Answer 25

• a joule per column

Question 26

2.21 relationship between energy transferred, charge and voltage:

Answer 26

energy transferred= charge x voltage

Question 27

P2 2.22 examples of electrical conductors:

Answer 27

metals, lead, copper, aluminium, gold, silver

Question 28

P2 2.22 examples of electrical insulators

Answer 28

glass, plastic, wood

Question 29

P2 2.23 PRACTICAL, investigate how insulating materials can be charged by friction:

Answer 29

• Hold polythene rod and cloth next to up small pieces of paper one at a time, observe.
• Now rub the rod with the cloth
• Again hold close to small pieces of paper, observe.
• Turn on a tap so a thin stream of water is flowing
• Hold the rod about 1cm away from the water just below the nozzle, observe
• Repeat with different material rods and cloths

Question 30

P2 2.24 explain how positive and negative electrostatic charges are produced on materials by the loss and gain of electrons;

Answer 30

• rub uncharged rod and uncharged cloth
• cloth becomes negative, rod becomes positive

Question 31

P2 2.25 what force is there between opposing charges?

Answer 31

repulsion

Question 32

P2 2.25 what force is there between like charges?

Answer 32

attraction

Question 33

P2 2.26 explain electrostatic phenomena in terms of the movement of electrons:

Answer 33

• Since electrons are negatively charged, the rod becomes positively charged
• As a result, the cloth has gained electrons and therefore is left with an equal negative charge

Question 34

P2 2.27 what are the potential dangers of electrostatic charges:

Answer 34

• build up of charge can cause a spark and then a fire

Question 35

P2 2.28 some uses of electrostatic charges:

Answer 35

• photocopiers
• inkjet printers
• paint spraying