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Physics GCSE > Electricity > Flashcards

Electricity Flashcards

1
Q

what is current

A

current is the rate of flow of charge. It is measured in Amps (A)

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2
Q

What is voltage (potential difference)

A

Voltage is the driving force that pushes the charge around.

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3
Q

What is resistance

A

Resistance is anything in the circuit which slows the flow down. Measured in Ohms

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4
Q

What is the operation of a Variable resistor

A

Variable resistors allow you to adjust the value of voltage by changing the current flowing into a component with resistance.

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5
Q

What is the operation of a diode

A

It acts as a one way switch that allows current to flow in one direction but restricts it from flowing the other with high resistance.

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6
Q

what happens when electrons bump into atoms

A

it can cause heat due to resistance. it can cause wires to get hotter

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7
Q

how to calculate current

A

Current = Charge
——————-
Time

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8
Q

how to calculate voltage

A

Voltage = Energy (work done)
————–
Charge

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9
Q

How to calculate resistance

A

Resistance = Voltage
————-
Current

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10
Q

How to measure current in a circuit

A
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11
Q

Ohms law

A

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature remain constant.

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12
Q

What might effect resistance

A
  • Current,
  • length of wire: more wire=more resistance
  • material of wire, some are better conductors
  • temp, higher temp = lower resistance
  • thickness, thinner wires conduct easier
  • parallel or series, parrallel= lower resistance and series= sum of all resistors
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13
Q

Resistance in a filament lamp

A
  • current increases so temp of lamp increases
  • the lamp is metal, so the raised temp causes an increased resistance
  • resistance opposes the current, causing the current to increase at a slower rate
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14
Q

Metal resistor IV graph

A

Has a constant gradient, so a constant resistance. This is because the current is directly proportional to potential difference

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15
Q

Bulb IV graph

A

has decreasing gradient, so an increasing resistance. This is because the wire gets hot.

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16
Q

Diode IV graph

A

has a low gradient (high resistance) until the threshold current.

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17
Q

What is a LDR

A

a resistor that is dependent on the intensity of light. If there is an increase of light, there is a decrease of resistance. Used often for automatic night lights, burgled alarms, outdoor lighting.

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18
Q

what is a thermistor

A

Temperature dependent resistor. If temp is increased resistance decreases. They’re used for car engines, thermostats and temp detectors

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19
Q

Current in a series circuit

A

Current is the same in any part of the circuit, this is because a series circuit is one loop; all electrons in that loop form one current

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20
Q

voltage in a series circuit

A

the potential difference supplied is equal to the total of the potential differences across all other components

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21
Q

Resistance in a series circuit

A

electrons have to pass through all resistors, so total resistance is sum of resistors.

Rtotal= R (1) + R(2) + R(3) +…

22
Q

Current in a Parallel Circuit

A

The overall current is shared between the loops

23
Q

Voltage in a Parallel circuit

A

the voltage is the same for each loop

24
Q

Resistance in a Parallel circuit

A

electrons have a choice of path so overall resistance = lower because the effective resistance is adding the reciprocals of the individual resistors

25
Q

filament lamp IV graph

A
26
Q

what does the amount of current flowing through a circuit depend on

A

Potential difference and resistance

27
Q

What two equations do you use to find power (watts)

A

Power = Voltage x current

or

Power = energy / time

28
Q

What does a switch do

A

A switch used to turn a circuit on (closed) and off (open).

29
Q

What does a lamp do

A

An electrical current heats the filament in a bulb so that it gives out light.

30
Q

What does a fixed resistor do

A

A resistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that does not change.

31
Q

What is charge

A

Charge is a property of a body which experiences a force in an electric field. Charge is measured in coulombs (C). There is more charge when there is more current.

32
Q

Equation for charge

A

charge = current × time

33
Q

What is direct current

A
  • flows in one direction
  • On a voltage-time graph this would appear as a straight horizontal line at a constant voltage
  • Car batteries, dry cells and solar cells all provide a direct current (dc) that only flows in one direction.
34
Q

What is alternating current

A

-An alternating current regularly changes direction. -alternating between positive and negative voltages on a voltage time graph - used in the mains electric supply

35
Q

Label the diagram

A
36
Q

What do you use an Ammeter for

A

Measuring current (in amps). It must always be in a series

37
Q

What does a voltmeter measure

A

Potential difference (volts), ALWAYS in parallel around whatever you are testing, not around any other bit

38
Q

What type of components have a straight line on an IV graph

A

Linear components (resistor or Ohmic conductor)

39
Q

What type of components have a curved line on an IV Graph

A

Non linear components ( filament lamp or a diode)

40
Q

How is alternating current produced

A

By alternating potential difference in which positive and negative ends keep alternating

41
Q

How is DC produced

A

Direct potential difference.

42
Q

How are electrical appliances connected to mains supply

A

3 core cables, they have a core of copper, coloured plastic coating

43
Q

What is the Neutral wire for

A
  • it completes the circuit - Current flows through it - It is blue
44
Q

What is the live wire for

A
  • provides the alternating provides the alternating potential difference from the mains supply - it is brown
45
Q

What is the earth wire for

A
  • protecting the wiring and safety
  • stops appliance casing from becoming live.
  • doesn’t carry current
  • Green and yellow
46
Q

What is a use for static charge and a danger

A
  • diffibrulators -explosions
47
Q

How might touching the live wire give you a shock

A
  • large potential difference is produced across your body, current flows thru you
  • causing an electric shock
  • because your body provides a link for the current to flow thru you between the supply and the earth
  • this can happen even if the plug socket is turned off = due to pd in live wire
48
Q

What is the National grid

A
  • system of cables and transformers,
  • connects power stations to consumers across the UK
49
Q

When does demand increase for electricity

A
  • people get up in morning
  • return home from work/school
  • when it gets dark or cold
  • popular events on TV
50
Q

What output do power stations run at

A
  • maximum output
  • so there’s spare capacity to cope with high demand
51
Q

What is the voltage in the national grid

A

400 000 V

52
Q

How does the step up transformers work

A
  • step up the potential difference at one end: for efficient transmission
  • step down for safe, unstable levels at the other end

Physics GCSE (8 decks)

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