P2-Electricity

Question 1

What is current?

Answer 1

The flow of electrical charge.

Question 2

What is potential difference (voltage)?

Answer 2

Is the driving force that pushes the charge round.

Question 3

What happens to the current when there is a great resistance?

Answer 3

The smaller the current that flows.

Question 4

Total charge through a circuit depends on what?

Answer 4

Current and Time.

Question 5

Formula for potential difference (V)?

Answer 5

Current (A) x resistance.

Question 6

What are the 3 different types of graphs about Resistance and I-V characteristics?

Answer 6

Ohmic conductor.
Filament Lamp.
Diode.

Question 7

Describe Ohmic conductors resistance?

Answer 7

Have a constant resistance.

Question 8

Does some resistor’s resistance change?

Answer 8

Yes. Some resistors and components does change e.g. a diode or filament lamp.

Question 9

What happens when an electrical charge flows through a filament charge?

Answer 9

It transfers some energy to the thermal energy store of the filament, which is designed to heat up.

Question 10

What happens when the current in the filament lamp increases?

Answer 10

Resistance increases with temperature, so as the current increases, the filament heats up more and the resistance increases.

Question 11

Describe the ohmic conductor? And graph?

Answer 11

The current through an ohmic conductor is directly proportional to potential difference. So you get a straight line.

Question 12

Describe filament lamp? And graph?

Answer 12

As the current increases, the temperature of the filament increases, so the resistance increases. This means less current can flow per unit, so the graph gets shallower- hence the curve.

Question 13

Describe diode? And graph?

Answer 13

Current will only flow through a diode in one direction. The diode has very high resistance in the reverse direction.

Question 14

What is an LDR?

Answer 14

Light Dependant Resistor.

Question 15

What is an LDR dependant on?

Answer 15

The intensity of light.

Question 16

What happens to the light in an LDR in terms of the resistance?

Answer 16

In bright light, the resistance falls.

In darkness, the resistance is highest.

Question 17

What is an LDR used for?

Answer 17

Applications including automatic night lights, outdoor lighting and burglar detectors.

Question 18

What is a thermistor?

Answer 18

Is a temperature dependant resistor.

Question 19

What does the resistance on a thermistor depend on?

Answer 19

Temperature.

Question 20

Describe the resistance of a thermistor in different temperature?

Answer 20

In hot conditions, the resistance drops.

In cool conditions, the resistance goes up.

Question 21

What are thermistors helpful for?

Answer 21

Temperature detectors, e.g. car engine temperature sensors and electronic thermostats.

Question 22

Describe how series circuits are connected?

Answer 22

The different components are connected in a line, end to end, between +ve and -ve of the power supply.

Question 23

What is potential difference sum in a series circuit?

Answer 23

Vtotal= V1 +V2.

Question 24

What is the sum of current in a series circuit?

Answer 24

i1=i2=i3……

Question 25

What is the resistance sum of series circuit?

Answer 25

R total = R1 + R2

Question 26

Describe connections in parallel circuits?

Answer 26

Each components is separately connected to +ve and -ve of the supply.

Question 27

What is potential difference sum in a parallel circuit?

Answer 27

V1 = V2 =........

Question 28

What is current sum in a parallel circuit?

Answer 28

I total = I1 + I2 + ......

Question 29

What is the current for Mains supply and for Battery supply?

Answer 29

Mains supply is ac (alternating current). | Battery supply is dc (direct current).

Question 30

What is the UK mains supply?

Answer 30

Is an ac supply at around 230 V.

Question 31

What is direct current?

Answer 31

Is a current that's always flowing in the same direction. | It's created by direct voltage.

Question 32

What are the 3 wires found in most electrical appliances?

Answer 32

Live wire. Neutral wire. Earth wire.

Question 33

What are the colours of the 3 wires?

Answer 33

Live wire = brown. Neutral wire = blue. Earth wire = green and yellow.

Question 34

What is live wire?

Answer 34

Provides the alternating potential difference (at about 230V) from the mains supply.

Question 35

What is the neutral wire?

Answer 35

Completes the circuit and carries away current - electricity normally flows in through the live wire and out through the neutral wire. It is around 0 V.

Question 36

What is the earth wire?

Answer 36

It is for protecting the wiring, and for safety - it stops the appliance casing from becoming live. It doesn't usually carry a current - only when there's a fault. It is at 0 V.

Question 37

What can the live wire cause?

Answer 37

Electric shock.

Question 38

How is energy transferred in electrical items?

Answer 38

Is transferred from cells and other sources.

Question 39

What is potential difference in terms of energy transferred?

Answer 39

Is energy transferred per charge passed.

Question 40

What does power depend on?

Answer 40

Current and potential difference.

Question 41

How is electricity distributed?

Answer 41

Via the National Grid.

Question 42

What is the National Grid?

Answer 42

Is a giant system of cables and transformers that covers the UK and connects power stations to consumers.

Question 43

How does the National grid transfer energy?

Answer 43

Through power stations.

Question 44

What is the Pd and low current like in the National grid?

Answer 44

High potential difference and low voltage.

Question 45

What is the negative of high current?

Answer 45

You lose loads of energy as wires heat up and energy is transferred to the thermal energy store of the surroundings.

Question 46

How is the Pd of the national grid changed?

Answer 46

By a transformer.

Question 47

Describe the stages of energy stages through national grid?

Answer 47

Power station -> step-up transformer -> cables -> step-down transformer -> consumers.

Question 48

What is a step-down transformer?

Answer 48

Converts high voltage to low. And low current to high.

Question 49

What is a step-up transformer?

Answer 49

Converts high voltage to low. And low current to high.