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Physics > Phyiscs Ka2 > Flashcards

Phyiscs Ka2 Flashcards

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1
Q

Where are semi conductors found?

A

On the boundary between metals and non-metals

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2
Q

Why is silicone a semi conductor?

A

Because it doesn’t have energy, they behave like insulator but with no free electrons. When we put in light they release electrons

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3
Q

What is a diode?

A

A diode is made of two pieces of semi-conductor, treated so the electrons will only flow directly across the boundary.

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4
Q

What happens to a diode in a circuit?

A

It allows current to flow easily on the forward direction, but not in the reverse direction

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5
Q

The sum of the p.d of the components in a series circuit = ???

A

The supply p.d (Vs = V1 + V2)

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6
Q

In a parallel circuit the p.d across each component = ???

A

The battery P.d (Vs = V1 = V2)

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7
Q

What is the striped wire and where is it?

A

The earth wire and at the top

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8
Q

What is the brown wire and where is it?

A

The live wire and on the right

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9
Q

What is the blue wire and what is its charge?

A

The neutral wire and on the left

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10
Q

What are the pins made of in a plug and why?

A

Brass because it is a good conductor and it is strong so it doesn’t bend and also won’t rust

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11
Q

What is the body of the plug made from and why?

A

Plastic because it is a good insulator

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12
Q

Why does the fuse melt?

A

When the current is too large so the circuit does not break

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13
Q

What does the cable grip in a plug do?

A

Stops the wire from being pulled out of place

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14
Q

What happens to the resistance of a filament lamp as the temperature of the filament increases?

A

It increases

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15
Q

A diode has a very ____ _____ in the reverse direction

A

High

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16
Q

What happens to the resistance of a light dependent resistor as the light intensity increases?

A

It decreases

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17
Q

Explain what happens to the lamp in the thermistor circuit

A

The brightness of the lamp increases as the current increases and the resistance decreases

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18
Q

Explain what must happen to the resistance in the LDR

A

The resistance decreases as the light intensity increases

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19
Q

Explain what must happen to the lamp in the LDR circuit

A

The brightness will increase as the resistance decreases and the current increases

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20
Q

In a series circuit, the ____ is the same value at any point in the circuit

A

Current

21
Q

In a parallel circuit the _____ of the current in each loop is equal to the _______ _______

A

Sum, current total

22
Q

In a _____ circuit each loop has the ____ P.d across it

A

Same

23
Q

What is the equation for power and what is it measured in?

A

Power= energy / time

Measured in W

24
Q

1W = _____

A

1J/s

25
Q

What is the equation for power in electricity?

A

Power = p.d x current

26
Q

What happens if the live in a washing machine is damaged?

A

The case will become live. The earth wire provides a low resistance path for the current to flow from the live wire

27
Q

What is an alternating current? (A.c)

A

Repeatedly reverses its direction. If flows one way then the other. It’s frequency is the number of cycles it passes through each second

28
Q

How much altering potential difference does a typical power station generate?

A

25000V

29
Q

When are step up transformers used

A

At power stations to transfer electricity to the national grid

30
Q

When are step down transformers used?

A

To supply electricity from the national grid to the consumers

31
Q

Why make the grid potential difference very large?

A

Much less current is needed to transfer the same amount of power, so the power loss due to the resistance hearing the cables is much reduced. This means the national grid is an efficient way to transfer power

32
Q

When is an oscilloscope used?

A

To show how an alternating potential difference changes with time

33
Q

The uk mains supply is about ____ volts

A

230

34
Q

Why does a mains cable have two or three inner cores of copper?

A

Because it’s a good conductor

35
Q

How much potential difference do the step up and step down transformers produce?

A

123000V

36
Q

What is the national grid?

A

The system of cables and transformers

37
Q

What happens to the electricity produced when a power station passes through a transformer

A

The voltage increases (step up transformer)

38
Q

What happens to the electricity when it reaches houses or factories?

A

It must have the voltage reduced (step down transformer) before it can be used safely

39
Q

Why do we use a high voltage in the cables?

A

To improve efficiency and reduce the waste heat

40
Q

When a current passes through it has a _____ heating effect. Energy is transferred from _____ to ______.

A

Heating, electrical, thermal

41
Q

The larger the _____ the lower the ______

A

Transfer, efficiency

42
Q

If we reduce the _____, by increasing the _____, the transmission system is more _______

A

Current, voltage, efficiency

43
Q

Power loss in a cable = ???

A

Current² x resistance

44
Q

The p.d of a battery is the ____ supplied to each _____ of _____ as it passes through the battery

A

Energy, coulomb, charge

45
Q

What is the equation for charge flow?

A

Charge flow= current x time

46
Q

What is the equation for energy transferred?

A

Energy transferred = charge flow x p.d

47
Q

What is the equation for total resistance?

A

Resistance total= R1 + R2

48
Q

What is the equation for potential difference?

A

P.d = current x resistance

Physics (5 decks)

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