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electricity Flashcards

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1
Q

What two factors does the current in the circuit depend on?

A

potential difference (V)
Resistance (R)

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2
Q

what is an Ohmic conductor state? The condition required?

A

A conductor for which current and potential difference are directly proportional

Resistance remains constant as current changes

temperature Must be constant

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3
Q

List four components for which resistance is not constant as current changes

A

lamps, diodes ,thermistor, light dependent resistors 

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4
Q

What happens to the resistance of a filament lamp as the temperature increases and why?

A

resistance increases

Irons and metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow

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5
Q

what is the different about current flow through a diode

A

The current only flows in One Direction

resistance is very high in other direction, preventing in current flow 

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6
Q

State what happens to the resistance of a thermistor as temperature increases

A

The thermistor resistance decreases

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7
Q

give two examples of when a thermistor may be used

A

in thermostat to turn the heater on below a certain temperature

In a freezer to turn on a cooler when the temperature becomes too high

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8
Q

State what happens to the resistor of LDR as light intensity decreases

A

The LDR resistance increases

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9
Q

Give an application for an LDR

A

Street lights often use ldr
when light levels become too low, the light gains sufficient current turn on 

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10
Q

what are the two ways that are component can be connected in a circuit?

A

Series(same loop)
Parallel (adjacent loop)

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11
Q

how does the potential difference across two components vary when connected in series and parallel? 

A

series: total potential difference is shared between each component

Parallel : potential difference across each component is the same

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12
Q

If two resistors are connected in parallel, what can be said about their combined total resistance?

A

Their total resistance is less than the smallest of the two individual resistances

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13
Q

If two resistors are connected in series, what can be said about their total resistance?

A

The total combine resistance is equal to the sum of the two individual resistances

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14
Q

Describe the current in a series circuit

A

In a series circuit, the current is the same at all positions since the charge only has one path to flow through

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15
Q

describe the current in a parallel circuit

A

In a parallel circuit, the current is shared between the different branches. When the charge reaches a junction it splits.

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16
Q

how should you connect ammeter in circuit to measure current?

A

Amita should be connected in series with the component that they are measuring current through

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17
Q

how should you connect voltmeter in circuit to measure potential difference?

A

voltmetre should be connected in a parallel to the component that they are measuring the potential difference of 

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18
Q

Why is it advantageous to connect lamps in parallel?

A

if one lamp blows, the rest will be unaffected and can still receive current

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19
Q

Is mains electricity an AC supply or a DC supply? What did each of these stand for?

A

mains electricity is an AC supply

AC: alternative current
DC: Direct current

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20
Q

Define alternating current and direct current

A

alternative current: current that continuous changes direction at a specific frequency

Direct current: One Direction current flow

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21
Q

What is the frequency and voltage of the UK mains electricity supply?

A

frequency:50 Hz
Voltage: 230V

22
Q

How many wires are usually in the cables connecting electrical appliances to the mains? Name these wires.

A
  1. Live wire.
  2. Neutral wire.
  3. Earth wire.
23
Q

State the insulation colour used on the earth wire

A

Green and yellow stripes

24
Q

State the insulation colour used on the live wire

A

Brown

25
Q

State the insulation colour used on the earth wire

A

Blue

26
Q

explain when the Earth wide does and doesn’t carry a current

A

In the normal circumstances, no current flows through the earth wire

 if a fault occurs in the appliance(such as a surge or the casing becoming live) current will flow to the ground

27
Q

What potential is the neutral wire at?

A

0 volts

28
Q

State the potential difference between the live and earth wire

A

230 v

29
Q

What is the purpose of a neutral wire?

A

To complete the circuit by connecting the appliance back to the main supply

30
Q

The metal appliances, where is the earth wire connected to and why?

A

Earth wire connected to the metal casing of the appliance

if live Wyatt becomes loose and touches the case in the current flow through the Earth by preventing electrocution

31
Q

what two main factors does the amount of energy transferred by appliance depend on

A

How long the appliances being used for?

The power of the appliance

32
Q

describe the energy transfer in a battery powered torch

A

battery converts chemical energy into electrical energy

bulb convert electrical energy into light as well as waste energy in the form of heating

33
Q

Describe the energy transfers in a battery powered motor

A

battery converts chemical energy into electrical energy

Motor converts electrical energy into kinetic energy as well as waste energy in the form of heating due to friction

34
Q

what three things determine the power of a circuit device?

A

The potential difference across the circuit

The current through the circuit

The amount of energy transferred in a given time

35
Q

What is the purpose of the national grid?

A

To link power stations to consumers so that they have access to source of electricity

36
Q

what are two types of transformers used in the national grid?

A

Step up transformer
Step down transformer

37
Q

Where are step up transformers found in the National Grid and what do they do?

A

step up transformers are used when connecting power stations to transmission cables

They increase the potential differences

38
Q

why do transmission lines transfer electricity at high potential?

A

At high potential result in a low current

The lower the current the less energy that is wasted as heat

Therefore, it is more efficient

39
Q

Why does the potential need to be creased between transmission lines and houses?

A

lower potentials are safer if it’s domestic use and reduces the likelihood of severe electrocution

appliances are designed for 230 V 

40
Q

what can happen when insulating a material of rubbed together?

A

They can become electrically charged

41
Q

why can insulators become electrically charged when rub together?

A

 electrons are rubbed from one material onto the other

The material gaining electrons become negatively charge

The material losing electron becomes equally positively charged

42
Q

What happens when two electrically charge objects are brought close together?

A

They exert force on each other

43
Q

what happens when two identical charge objects are put close together?

A

The repulsive force on each other and repel

44
Q

What happens when two opposite charge objects are brought close together?

A

they exert an attractive force on each other and attract

45
Q

Give an example of a noncontact force

A

they repulsive or attract force acting between two electrically charge objects

46
Q

What is an electric field?

A

Region in which a charge objects will experience a noncontact electrical force

47
Q

Where can electric fields be found?

A

Surrounding any charged object

48
Q

describe the electric field around a charge particle

A

Strongest closest to the object
Decreases in strength as you move away from the object

49
Q

What happens to the force between two charge objects when they moved closer together?

A

The force between them becomes stronger as the separation reduces

50
Q

In situations where sparks are unwanted what precaution must be taken to prevent the buildup of static charge

A

Any surfaces that are rubbing against each of us should be earth to allow the charge to flow off the materials

physics (6 decks)

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