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Electricity Flashcards

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1
Q

Electrical circuits explained

A

Energy is supplied to electrons by a cell/battery or mains electricity. Which then move through the wires to transfer energy. Cells/ batteries have a store of chemical energy.

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2
Q

What is current

A

The rate of the flow of charge

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3
Q

How do electrons move in a circuit

A

The charge travels from the cell/battery to the lamp where all of their energy is converted into light

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4
Q

What is potential difference

A

The measure of how much is energy is transferred to each coulomb of electrons/charge. Unit:volt(V)

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5
Q

Where are voltmeters connected

A

Parallel to components

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6
Q

Potential difference equation ET=C

A

Potential difference = energy transferred(J) / charge(c)

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7
Q

Where are ammeter always components

A

In series with components

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8
Q

Resistance meaning

A

The measure of how much a component/object resists the flow of current. Unit ohms

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9
Q

Potential difference equations

A

Potential difference = current(A) x resistance(ohms)

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10
Q

Fixed resistor explained

A

Straight line t1hrough origin. V and I are (directly proportional, constant gradient = constant R

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11
Q

Filament lamp explained

A

Line curves, resistance not constant. This is due to delocalised electrons colliding with ionic lattice which causes them to vibrate more. A larger current results in an increased resistance(non-ohmic)

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12
Q

Led-diode explained

A

Diodes only let current flow in one direction:low resistance in forward directions. High resistance in reverse directions

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13
Q

Series circuit features

A

Total P.D is shared between all components
Current is the same for all components
Total resistance = sum of resistances

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14
Q

Parallel circuit features

A

P.D for each branch=P.d of cell/battery
Current is split between the branches
Adding more resistors in parallel reduces total resistance

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15
Q

Thermistor explained

A

Does the opposite to a metal/filament. If temperatures increases, resistance decreases.

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16
Q

LDR explained

A

Similar to a thermistor but for light: if light intensity increases, resistance decreases.

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17
Q

What is direct p.d

A

A p.d that only acts in one direction(results in D.C(direct current) e.g. from a battery

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18
Q

Describe Neutral wire

A

Blue wire. Stays at 0v

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19
Q

Live wire

A

Changes between positive and negative potentials which average out a 230 V this is UK mains voltage.
Brown wire

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20
Q

Earth wire

A

Safety feature it acts as an escape route for a current that would otherwise cause a shock if the appliance is touched. Not needed for double insulated appliance

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21
Q

What type of current is main electricity

A

Alternating current. Resulting from an alternating P.D. (Both of these reverse direction at frequency of 50HZ, at least in the UK)

22
Q

National grid definition

A

Distributes electricity to where its needed

23
Q

Power station

A

Produce a relatively high current. If this went straight into the grid, a huge amount of energy/power would be lost as heat due to the resistance of cables.

24
Q

Step up transformer

A

Increases the transmission voltage to 132KV(132,000V) which decreases the current, less power lost due to heating in the cables.

25
Q

What is static electricity

A

Transferred between insulating materials, they will remain charged - this is static electricity

26
Q

What is the magnetic law

A

Opposite charges attract and like charges repel

27
Q

Electron law explained

A

Electrons are negatively charged so if an object gains electrons, it becomes negatively charged if it loses them it becomes positively charged.

28
Q

Writer the equation that links current, potential difference and power

A

Current = power/potential difference

29
Q

What is potential difference

A

P.D is the measure of how much energy is transferred to/by each coulomb of electrons/charge

30
Q

How are voltmeters connected

A

Always connected in parallel

31
Q

What is current

A

The rate of flow of charge

32
Q

How are ammeters connected

A

Always connected in series with component

33
Q

What is resistance

A

The measure of how much a component/object resists the flow of charge unit ohms

34
Q

What relationship do current and potential have

A

Directly proportional

35
Q

Describe fixed resistor graph

A

Straight line through origin : potential difference and current are directly proportional. Constant gradient = constant resistance. It is ohmic. If another resistor gives a steeper gradient, it must have a lower resistance

36
Q

Describe filament lamp graph

A

Line curves : resistance is not constant. This is due to delocalised electrons colliding either ionic lattice, which causes them to vibrate more, and temperature increase. A large current results in an increased resistance (Non ohmic)

37
Q

Describe diode graph

A

Diodes only let current flow in one direction: low resistance in forward direction. High resistance in reverse direction

38
Q

Describe series circuits

A

Total potential difference is shared between all components.
Current is the same for all components.
Total resistance = sum of resistances
If resistors are identical, total V must be shared equally. If not, the bigger resistance takes a bigger share of voltage.

39
Q

Describe parallel circuits

A

Potential difference for each branch = potential difference of cell/battery
Current is split between the branches
Adding more resistors in parallel reduces the total resistances

40
Q

Describe a thermistor

A

Does the opposite to a metal/filament : if temperature increases, resistance decreases.

41
Q

Describe an LDR(light dependent resistor)

A

Similar to a thermistor, but for light: if light intensity increases, resistances does

42
Q

What’s is direct potential difference

A

Potential difference that only acts in one direction. This results in direct current(D.C) e.g. from a battery

43
Q

Describe mains electricity in terms of current and potential differences

A

Alternating current resulting from an alternating potential difference

44
Q

What voltage is the neutral wire

A

Stays at 0 volts

45
Q

What voltage is the live wire

A

Changes positive + negative potentials, which average out at a P.D of 230V - this is the u.k mains voltage

46
Q

Describe the earth wire

A

Safety feature : it acts as an escape froute for current that would otherwise cause a shock if the appliance is touched. Not needed for double insulated appliances.

47
Q

What colour wire is the neutral earth and live

A

Live wire - brown
Neural wire - blue
Earth wire - yellow and green

48
Q

What do power stations do in the national grid

A

Produce a relatively high current. If this went straight into the grid, a huge amount of energy/power would be lost and heat due to the resistance of the cables

49
Q

What does a step up transformer do in the national grid

A

Increases the voltage(132Kv), which decreases the current, reducing the power lost due to heating in the cables.

50
Q

What does a step down transformer do

A

Reduces the voltage down to a safer and usable 230V for homes and businesses

physics (15 decks)

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