Section 2 - Electricity

Question 1

Three types of wire in a plug?

Answer 1

• Live wire(brown)
• Neutral wire(blue)
• Earth wire(green/yellow)
• p18

Question 2

Metal parts are made of…

Answer 2

Copper or brass(good conductors)

Question 3

The rest of the plug is made of…

Answer 3

rubber or plastic(good insulators and flexible)

Question 4

The live wire

Answer 4

-Alternates between high +VE and -VE voltage of about 230V

Question 5

The neutral wire

Answer 5

-Is always at 0V

Question 6

The earth wire

Answer 6

• Earths the appliance
• Carries the current away if a fault develops
• An earthed conductor can never become live

Question 7

Normal flow of electricity in a plug

Answer 7

In through the live wire and out through the neutral wire

Question 8

How the earth wire and the fuse works

Answer 8

• A fault develops where the live wire touches the metal case
• A large current flows through the live, through the case, then out down the earth wire
• The surge melts the fuse(or trips the circuit breaker)
• This isolates the appliance, making it impossible to get an electric shock

Question 9

Advantage of a surface breaker

Answer 9

• It opens a switch when a surge is detected
• This breaks the the circuit
• Can be easily reset

Question 10

Resistors

Answer 10

• Heat up when there is an electric current
• Heat increases the resistance of a resistor
• Therefore less current will flow
• This can cause components to melt

Question 11

Formula for electrical power

Answer 11

P = I*V

Question 12

What is electrical power?

Answer 12

Electrical power is the rate at which an appliance transfers energy

Question 13

What does a higher power rating mean?

Answer 13

More energy is transferred in a short time; thus the appliance will draw a large current from the supply

Question 14

Unit for power

Answer 14

watts(W)

Question 15

Rating of fuses

Answer 15

Fuses should be rated as near as possible, but slightly higher than the normal operating current

Question 16

Formula for energy transferred

Answer 16

E = IVt

Question 17

Current

Answer 17

The rate of flow of charge round the circuit(A)

Question 18

Voltage

Answer 18

The energy transferred per unit charge passed

Question 19

Resistance

Answer 19

Anything in the circuit which slows the flow down(Ω)

Question 20

Effect of increasing the voltage

Answer 20

More current will flow

Question 21

Effect of increasing the resistance

Answer 21

Less current will flow

Question 22

Formula for voltage

Answer 22

V = I*R

Question 23

Voltage-current graphs

Answer 23

Metal filament lamp - As temperature increases, the resistance increases
Wire - The current through a wire(at constant temperature) is proportional to voltage
Different Resistors - The current through a resistor is proportional to voltage
Diode - Current will only flow through a diode in one direction
p22

Question 24

LEDs

Answer 24

• Light emitting diodes
• Emit light when current flows through them in the forward direction
• Don’t have a filament that can burn out

Question 25

LDR

Answer 25

- Light-dependant resistor - As light increases, the resistance decreases - As light decreases, the resistance increases

Question 26

Thermistor

Answer 26

- A temperature-dependant resistor - As heat increases, the resistance decreases - As heat decreases, the resistance increases

Question 27

Layout in a series circuit

Answer 27

All the components are connected in a line

Question 28

Characteristics of a series circuit

Answer 28

- Cannot control which components current flows through - Removing or disconnecting one component will break the circuit - Only a few things are connected in series(e.g fairy lights) - The same current flows through all parts of the circuit - Size of the current is determined by the total voltage of the cells, and the total resistance of the circuit - The total resistance depends on the number of components and the type of components used

Question 29

Layout in a parallel circuit

Answer 29

Each component is separately connected to the +VE and -VE of the supply

Question 30

Characteristics of a parallel circuit

Answer 30

-Removing or disconnecting one of the components will hardly affect the others

Question 31

How is charge carried in a solid metal conductors?

Answer 31

By negatively charged electrons

Question 32

Formula for charge

Answer 32

Q = I*t

Question 33

Definition of a volt

Answer 33

One volt is one joule per coulomb

Question 34

How does static build up?

Answer 34

- Two insulating materials are rubbed together - The electron are scrapped off one and dumped onto the other - This results in opposite electrostatic charges - Electrically charged objects attract small objects placed near them

Question 35

How can negative charge be discharged safely?

Answer 35

By connecting the charged conductor to the earth with a metal strap: The electrons flow down the strap if the charge is negative, and flow from the ground if the charge is positive

Question 36

How are sparks caused by static electricity?

Answer 36

The greater the charge on an isolated object, the greater the voltage between the object and the earth: When the voltage gets great enough, a spark is created which jumps across the gap