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P12- ELECTRIC CURRENT > 12.4- COMPONENTS AND THEIR CHARACTERISTICS > Flashcards

12.4- COMPONENTS AND THEIR CHARACTERISTICS Flashcards

1
Q

What is a cell a source of?

A

electrical energy

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2
Q

What is a battery a combination of?

A

combination of cells

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3
Q

What does a diode allow?

A

current in one direction only

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4
Q

What does a light-emitting diode (LED) do when it conducts?

A

emits light when it conducts

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5
Q

What is the direction that a diode conducts referred to as?

A

its forward direction

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6
Q

What is the opposite direction that a diode conducts referred to as?

A

reverse direction

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7
Q

Example of use of diode?

A

protection of dc circuits

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8
Q

What is a resistor designed to have?

A

certain resistance

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9
Q

What happens to the resistance of a thermistor as the temp increases, if the thermistor is an intrinsic semiconductor i.e. silicon?

A

resistance decreases

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10
Q

What happens to the resistance of a light-dependent resistor (LDR) with increasing light intensity?

A

resistance of LDR decreases with increasing light intensity

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11
Q

To measure the variation of current with pd for a component, what should you use? (2)

A

potential divder to vary pd from zero
OR
variable resistor to vary current to minimum

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12
Q

What is the advantage of using a potential divided when measuring the variation of current?

A

current through component + pd across it can be reduced to zero
not possible with variable resistor circuit

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13
Q

What kind of IV graph does a wire give?

A

straight line through origin

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14
Q

What does the IV graph of a wire being a straight line through the origin mean?

A

means that any point on line, value of V/I same

resistance constant

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15
Q

What kind of IV graph does a filament bulb give and why?

A

curve with decreasing gradient as its resistance increases as it becomes hotter

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16
Q

What kind of IV graph does a thermistor at constant temp give?

A

straight line

higher the temp, greater the gradient of the line- resistance falls with increase of temp

17
Q

What else has has the same IV graph as a thermistor at constant temp?

A

LDR in respect of light intensity

18
Q

Above what pd does a silicon diode conduct easily in its forward direction?

A

above pd of about 0.6V and hardly at all below 0.6V or in opposite direction

19
Q

How does the resistance of a metal change with temperature?

A

resistance of metal increases with increase of temp

20
Q

Why does the resistance of a metal increase with increase of temp?

A

as positive ions in conductor vibrate more when its temp increased
so conduction electrons cannot pass through metal as easily when pd applied across conductor

21
Q

Why is a metal said to have a positive temperature coefficient?

A

as its resistance increases with increase of temperature

22
Q

How does the resistance of an intrinsic semiconductor change with temperature?

A

resistance of intrinsic semiconductor decreases with increase of temp

23
Q

Why does the resistance of an intrinsic semiconductor decreases with increase of temp?

A

number of conduction electrons increases when temp increased

24
Q

What is a thermistor made from?

A

an intrinsic semiconductor

25
Q

As a thermistor has an intrinsic semiconductor, what does it has?

A

a negative temperature coefficient

26
Q

What is the percentage change of resistance per kelvin change of temperature of a thermistor like in comparison to a metal?

A

much greater than for a metal

27
Q

As the percentage change of resistance per kelvin change of temperature of a thermistor is much greater than for a metal, what are they often used as?

A

temperature-sensitive component in temp sensor

28
Q

How does the resistance of a thermistor decrease with increase of temp?

A

resistance of thermistor decreases non-linearly with increase in temp

P12- ELECTRIC CURRENT (4 decks)

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