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Lamda > Electricity Part 2 > Flashcards

Electricity Part 2 Flashcards

1
Q

The resistance of a light dependant resistor decreases…

A

As light intensity increases

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2
Q

The resistance of a thermistor decreases…

A

As the temperature increases

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3
Q

What is the forward resistance for a diode like?

A

Low resistance so reverse resistance is high so there is negligible current in the reverse direction

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4
Q

What happened to the resistance of a LDR as light intensity increases?

A

Resistance of the LDR decreases at light intensity increases

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5
Q

What happens to the resistance of a thermistor as the temperature increases?

A

The resistance of the thermistor decreases as the temperature increases

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6
Q

What is the current through each component for a component connected in series?

A

The current through each component is the same for components connected in series

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7
Q

How can you calculate the total potential difference of components in series?

A

Adding the potential differences of each component gives the total PD

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8
Q

What is the total resistance of components connected in series?

A

The sum of the resistance of each component

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9
Q

What is the total current of component connected in parallel?

A

The sum of the currents through the separate components

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10
Q

What is the potential difference of each component in parallel?

A

The potential difference across each component is the same

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11
Q

For components connected in parallel the bigger the resistance ……………

A

The smaller the current

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12
Q

How can you calculate the current through a resistor in parallel?

A

Using the equation I= V/R

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13
Q

What is direct current?

A

Current that travels in one direction only

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14
Q

What is alternating current?

A

Current that repeatedly reverses

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15
Q

What is the peak voltage of an alternating potential difference?

A

The maximum voltage measured from zero volts

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16
Q

What Dee’s the live wire alternate between?

A

Alternates between positive and negative every cycle

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17
Q

What voltage is the neutral wire at?

A

Zero volts

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18
Q

In the uk what does the voltage alternate between?

A

325 and -325V

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19
Q

What is 325 and -325 in alternating current equal to in direct current?

A

230 in direct voltage

20
Q

How can you measure the frequency of an a.c supply?

A

Measure the time period of the waves and then use the formula frequency = 1/time taken for one cycle

21
Q

In the uk what is the mains supply frequency?

A

50Hz

22
Q

What are sockets and plugs made of? And why?

A

They are made of stiff plastic that enclose the electrical connections
Plastic is used as it is a good electrical insulator

23
Q

An appliance with a plastic case is said to be …………. …………….

A

Doug,y insulated

24
Q

What do mains cables consist of?

A

2 or 3 insulated copper wires surrounded by an outer layer of flexible plastic material

25
Q

What colour is the live wire?

A

Brown

26
Q

What colour is the neutral wire?

A

Blue

27
Q

What colour is the earth wire?

A

Green and yellow

28
Q

Which pin is the earth wire connected to?

A

The longest pin

29
Q

What is the earth wire used for?

A

It is used to earth the metal case of a mains appliance

30
Q

What is a fuse?

A

A thin wire that heats up and melts cutting of the current if the current is too large

31
Q

How is a fuse fitted?

A

It is fitted in series with the live wire so if the fuse blows ipthe current from the live wither is cut off

32
Q

What is a circuit breaker?

A

An electromagnetic switch that opens and cuts off the current in the live wire if too much current passes through the circuit breaker

33
Q

Why is a circuit breaker better than a fuse?

A

It works faster

Can be reset quickly

34
Q

What does RCCB stand for?

A

Residual current circuit breaker

35
Q

What does a RCCB do?

A

Cuts off the current in the live wire if it is different from the current in the neutral wire

36
Q

What is the benefit of RCCB?

A

It is more sensitive than both a fuse and a circuit breaker

37
Q

Why does a mains appliance with a plastic case not need to be earthed?

A

Plastic is an insulator and cannot become live

38
Q

Why should appliances with metal cases be earthed?

A

So that if a fault occurs the metal case is safe to touch

39
Q

What is power?

A

The energy transferred to an appliance each second

40
Q

When an electrical charge through a resistor ……….. ………… To the resistor makes it …..

A

Energy
Transferred
Hot

41
Q

When a ……. Flows round a circuit for a certain time the ……….. Energy supplies by the battery is ……….. To the electrical energy transferred to ….. Components in the circuit

A

Charge
Electrical
Equal
All

42
Q

Why are electrical faults dangerous?

A

They can cause electric shocks and fires

43
Q

What should you consider when choosing an appliance?

A

Power and efficiency

44
Q

Filament bulbs and halogen bulbs are much ……. Efficient than ….. Energy bulbs

A

Less

Low

45
Q

You should tough a mains appliance or plug or wicket with ….. …… And should never touch a bare wire or terminal at a potential of more than ……

A

Wet hands

30V

Lamda (4 decks)

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