Elctricity

Question 1

2.2. How does insulation protect the device or user in a range if domestic appliances

Answer 1

.plastic is an insulator so current cannot pass through it meaning no risk of electric shock

Question 2

2.2. How does double insulation protect the device or user in a range of appliances

Answer 2

.plastic is an insulator so no current can pass through so no risk of electric shock

Question 3

2.2. How does earthing protect the device or the user in a range of appliances

Answer 3

Allows any accumulated charge to flow back to the ground so that object remains neutral so no risk of shock

Question 4

2.2. How do fuses help to protect the device or the user in a range of different appliances

Answer 4

If there is a surge of current the fuse blows and breaks circuit meaning charge no longer runs in the circuit so no risk of overheating and causing fires

Question 5

2.2 How do circuit breakers protect the device or user in a range of domestic appliances

Answer 5

An electrical switch that breaks the circuit when there is a surge of current stopping the appliance overheating and causing fires

Question 6

2.3. Why does current in a resistor result in a temperature increase

Answer 6

When current flows in a resistor the free electrons collide with metal ions in the resistor and transfer energy to the lattice in the form of heat

Question 7

2.4. What is the relationship between power current and voltage

Answer 7

P = I V
Power = current x voltage
(W or J/s) = (amps) x (volts)

Question 8

2.5. What is the relationship between energy transferred, curèrent, voltage and time

Answer 8

Energy transferred = current x voltage x time
E = I V t
(Joules) = (amps) (volts) (seconds)

Question 9

2.6. What is the difference between mains electricity and electricity supplies by a cell or battery

Answer 9

Mains : A.C. (Alternating current)
Cell or battery : D.C. (direct currrent)

Question 10

2.6. What is the difference between alternating current and direct current

Answer 10

A.C.: quickly changes direction so that the electrons end up vibrating on the spot and dont move anywhere
D.C.: goes around a circuit from positive to negative and is therefore always above zero in that direction

Question 11

2.7Why is a series or parallel circuit more appropriate for particular applications including domestic lighting

Answer 11

.in a series circuit, if one appliance stops working, all the lights go out
.in a parallel circuit, if one appliance stops working, only the other appliances on that branch will stop working

Question 12

2.8. Why does current in a circuit depend on the applied voltage and the number and nature of other components

Answer 12

.any component added to the circuit will increase the resistance in the circuit, this will decrease the the current
.increase voltage - more current will flow
.increase resistance - less current will flow

Question 13

2.9. How does current vary with voltage in wires, resistors, metal filament lamps and diodes?

Answer 13

.resistors: straight line through the origin
.filament lamp: f shape
.diode: die=dead= flat lining

Question 14

2.10 what happens to the current if you change the resistance in a circuit

Answer 14

. If you increase existence, current decreases
.if you decrease resistance, current increases

Question 15

2.11. What is the effect on resistance if you increase the light intensity on a circuit with an LDR

Answer 15

As light intensity detected by the LDR increases its resistance decreases (non-linear relationship)

Question 16

2.11. What is the effect on resistance when you increase the temperature in a circuit with a thermistor

Answer 16

As temperature detected by the thermistor increases, the resistance decreases (non-linear relationships)

Question 17

2.12. What can lams and LED’s ne used to indicate the presence of in a circuit

Answer 17

Current

Question 18

2.13. What is the relationship between voltage current and resistance

Answer 18

V= I R
Voltage = current x resistance
(Volts) = (amps) (ohms)

Question 19

2.14. What is current

Answer 19

The rate of flow of charge

Question 20

2.15. What is the relationship between charge current and time

Answer 20

Q = I t
Charge = current x time
(Coulombs) = (amps) (seconds)

Question 21

2.16. What is current in solid metallic conductors

Answer 21

A flow of negatively charged electrons

Question 22

2.18. Does voltage change across two components connected in parallel

Answer 22

No

Question 23

2.20. What is voltage

Answer 23

The energy transferred per unit charge passed

Question 24

2.20. What is a volt

Answer 24

A joule per coulomb

Question 25

2.21. What i the relationship between energy transferred, charge and voltage

Answer 25

E = Q V
Energy transferred = charge x voltage
(Joules) (Coulombs) (volts)

Question 26

2.22P. Identify two common materials that are electrical conductors or insulators

Answer 26

Conductors : metals - copper and aluminium
Insulators : plastic

Question 27

2.23P. Describe a practical investigating how materials can be charged by friction

Answer 27

Using a cloth, rub Perspex and polythene in one direction only.
.polythene: electrons transferred from the cloth to the rod causing the rod to have a negative charge and the cloth to have a positive charge
.Perspex: electrons transferred from the rod to the cloth causing the rod to have a positive charge and the cloth to have a negative charge

Question 28

2.24P. Explain how positive and negative electrostatic charges are produced on materials by the loss and gain of electrons

Answer 28

.when an object loses electrons it gains a positive charge because there are no electrons to neutralise the charge
.when an object gains electrons it gains a negative charge because electrons have a negative charge

Question 29

2.25P. What happens to like charges and unlike charges

Answer 29

Unlike : attract
Like : repel

Question 30

2.27P. Explain some of the dangers of electrostatic charges

Answer 30

.sparks
.fires
.explosions

Question 31

2.28P. Explain some of the uses of electrostatic charges

Answer 31

.photocopiers and printers
.paint spraying