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Physics GCSE > P2-Electricity > Flashcards

P2-Electricity Flashcards

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1
Q

What is current?

A

The flow of electrical charge.

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2
Q

What is potential difference (voltage)?

A

Is the driving force that pushes the charge round.

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3
Q

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

A

The smaller the current that flows.

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4
Q

Total charge through a circuit depends on what?

A

Current and Time.

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5
Q

Formula for potential difference (V)?

A

Current (A) x resistance.

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6
Q

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

A

Ohmic conductor.
Filament Lamp.
Diode.

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7
Q

Describe Ohmic conductors resistance?

A

Have a constant resistance.

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8
Q

Does some resistor’s resistance change?

A

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

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9
Q

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

A

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

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10
Q

What happens when the current in the filament lamp increases?

A

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

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11
Q

Describe the ohmic conductor? And graph?

A

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

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12
Q

Describe filament lamp? And graph?

A

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.

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13
Q

Describe diode? And graph?

A

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

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14
Q

What is an LDR?

A

Light Dependant Resistor.

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15
Q

What is an LDR dependant on?

A

The intensity of light.

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16
Q

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

A

In bright light, the resistance falls.

In darkness, the resistance is highest.

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17
Q

What is an LDR used for?

A

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

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18
Q

What is a thermistor?

A

Is a temperature dependant resistor.

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19
Q

What does the resistance on a thermistor depend on?

A

Temperature.

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20
Q

Describe the resistance of a thermistor in different temperature?

A

In hot conditions, the resistance drops.

In cool conditions, the resistance goes up.

21
Q

What are thermistors helpful for?

A

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

22
Q

Describe how series circuits are connected?

A

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

23
Q

What is potential difference sum in a series circuit?

A

Vtotal= V1 +V2.

24
Q

What is the sum of current in a series circuit?

A

i1=i2=i3……

25
Q

What is the resistance sum of series circuit?

A

R total = R1 + R2

26
Q

Describe connections in parallel circuits?

A

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

27
Q

What is potential difference sum in a parallel circuit?

A

V1 = V2 =……..

28
Q

What is current sum in a parallel circuit?

A

I total = I1 + I2 + ……

29
Q

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

A

Mains supply is ac (alternating current).

Battery supply is dc (direct current).

30
Q

What is the UK mains supply?

A

Is an ac supply at around 230 V.

31
Q

What is direct current?

A

Is a current that’s always flowing in the same direction.

It’s created by direct voltage.

32
Q

What are the 3 wires found in most electrical appliances?

A

Live wire.
Neutral wire.
Earth wire.

33
Q

What are the colours of the 3 wires?

A

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

34
Q

What is live wire?

A

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

35
Q

What is the neutral wire?

A

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.

36
Q

What is the earth wire?

A

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.

37
Q

What can the live wire cause?

A

Electric shock.

38
Q

How is energy transferred in electrical items?

A

Is transferred from cells and other sources.

39
Q

What is potential difference in terms of energy transferred?

A

Is energy transferred per charge passed.

40
Q

What does power depend on?

A

Current and potential difference.

41
Q

How is electricity distributed?

A

Via the National Grid.

42
Q

What is the National Grid?

A

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

43
Q

How does the National grid transfer energy?

A

Through power stations.

44
Q

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

A

High potential difference and low voltage.

45
Q

What is the negative of high current?

A

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

46
Q

How is the Pd of the national grid changed?

A

By a transformer.

47
Q

Describe the stages of energy stages through national grid?

A

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

48
Q

What is a step-down transformer?

A

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

49
Q

What is a step-up transformer?

A

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

Physics GCSE (8 decks)

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