Topic P2 - Electricity Flashcards

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1
Q

Current definition

A

Flow of electrical charge

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2
Q

What is current measured in?

A

Ampere, A

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3
Q

Potential difference definition

A

Driving force that pushed charge round

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4
Q

What is potential difference measured in?

A

Volt, V

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5
Q

Resistance definition

A

Anything that slows down charge flow

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6
Q

What is resistance measured in?

A

Ohm, Ω

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7
Q

Current through a component depends on two factors:

A

1)
The component’s resistance

  • The greater the resistance, the smaller the current.

2)
The potential difference across the component.

  • The greater the potential difference, the larger the current (for a fixed resistance).
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8
Q

Size of current = rate of…

A

Size of current = rate of flow of charge

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9
Q

Charge flow formula

A

Q = It

Q - charge flow (C)
I - current (A)
t - time (s)

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10
Q

What is charge flow measured in?

A

Coulombs, C

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11
Q

Potential difference equation

A

V = IR

V - Potential Difference (V)
I - Current (A)
R - Resistance (Ω)

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12
Q

For circuit symbols look at page 83.

A

For circuit symbols look at page 83.

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13
Q

What are the 3 different I-V characteristics?

A

1) Ohmic conductors at constant temperature
2) Filament Lamp
3) Diode

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14
Q

I-V ohmic conductor at constant temperature graph characteristics

A

Current is directly proportional to potential difference so resistance doesn’t change.

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15
Q

Current is directly proportional to potential difference…

A

…so resistance doesn’t change

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16
Q

Is an ohmic conductor I-V graph liner or non-linear?

A

Linear

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17
Q

What are 4 examples of components with changing resistances when the current through them varies?

A

1) Filament Lamp
2) Diode
3) LDR
4) Thermistor

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18
Q

I-V, filament lamp graph characteristics

A

Current increase so temperature of filament increases so resistance increases.

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19
Q

I-V, diode graph characteristics.

A

High resistance in one direction so current only flows in the other direction.

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20
Q

Are filament lamps and diode graphs linear or non-linear.

A

Non-linear

21
Q

An LDR resistance depends on?

A

Light intensity

22
Q

An LDR has lower resistance in?

A

Brighter light

23
Q

LDRs are used in?

A

Automatic night lights

24
Q

A thermistors resistance depends on?

A

Temperature

25
Q

A thermistors has lower resistance in?

A

Hotter temperatures

26
Q

Thermistors are used in?

A

Thermostats

27
Q

What are the 2 types of electricity supply?

A

1) Alternating current

2) Direct Current

28
Q

Alternating current (ac) definition

A

Current that constantly changes direction and is produced by an alternating voltage. Used in mains supply.

29
Q

Direct Current (dc) definition

A

Current that always flows in the same direction and is produced by a direct voltage. Supplied by batteries.

30
Q

When charge flows, work is done and so…

A

When charge flows, work is done and so energy is transferred

31
Q

How is energy transferred from a plug socket to a kettle?

A

Energy is transferred electrically, to thermal energy store of the heating element inside the kettle.

32
Q

How is energy transferred from a battery to a fan?

A

Energy is transferred electrically, the the kinetic energy store of the fan’s motor.

33
Q

Energy transfer formulas

A

E = QV

E = Pt

E - energy transferred ( J )
Q - charge flow (C)
V - Potential Difference (V)
P - power (W)
t - time (s)
34
Q

Amount of energy an appliance transfers depends on:

A
  • appliance’s power

- how long appliance is on for

35
Q

Power definition

A

Energy transferred per second

36
Q

Power rating definition

A

Maximum safe power an appliance can operate at.

37
Q

Power formulas

A

P = VI

P = I²R

P - power (W)
V - potential difference (V)
I - current (A)
R - resistance (Ω)

38
Q

National grid definition

A

A system of cable and transformers that connect power stations to consumers

39
Q

What does a step-up transformer do?

A

Increases potential difference

40
Q

What does a step-down transformer do?

A

Decreases potential difference

41
Q

How can electrical power be transferred efficiently?

A

High potential difference and a low current.

42
Q

What would happen if electrical power was transferred at a high current?

A

Wires would heat up and transfer a lot of energy to the thermal energy stores of the surroundings.

43
Q

Density formula

A

p = m/v

p - density (kg/m³)
m - mass (kg)
v - volume (m³)

44
Q

What is density’s unit?

A

kg/m³

45
Q

What can increased internal energy of a system do?

A

1) Increase temperature

2) Change in state

46
Q

The higher the temperature of a gas, the higher the average energy…

A

In the kinetic energy stores of the gas particles

47
Q

Gas pressure is caused by…

A

Gas particles colliding with a surface and exerting a net force on it.

48
Q

If a gas at a constant volume has a temperature increase what will happen?

A

Gas particles get faster and collide with the container more often, leading to a pressure increase