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Physics > P3.2 > Flashcards

P3.2 Flashcards

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1
Q

What is the link between potential difference, energy and charge?

A

Potential difference (V)
Energy transferred (J) = ———————————
Charge (C)

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2
Q

What is potential difference measured in?

A

Volts

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3
Q

How do you measure current in a series circuit?

A

With an ammeter

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4
Q

How do you measure potential difference in series circuits?

A

With a voltmeter

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5
Q

What happens when two voltmeters are in series?

A

They add up to give the total potential difference

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6
Q

What happens when 2 voltmeters are parallel?

A

They are both equal to the total potential difference

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7
Q

What is the formula for potential difference?

A

Potential difference = resistant x current

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8
Q

Why do some components have resistance?

A

They have ions in a fixed lattice and when the flow of electrons from the wire collides with the ions, resistance and what is formed

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9
Q

What is a variable resistor?

A

A circuit component that you can use to change the amount of wire or other resisting material

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10
Q

Why is a graph of resistance to potential difference linear?

A

As you increase potential difference, it’s resistance does not change

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11
Q

What do you use in a circuit if you need the resistance to be constant?

A

A resistance wire or a resistor

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12
Q

What is Ohm’s law?

A

The current is proportional to the potential difference if the temperature does not change

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13
Q

What is a diode?

A

A component that only allows a current to flow one way

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14
Q

What does LED stand for?

A

Light-Emitting Diode

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15
Q

How do connect an LED to a battery?

A

The long led of an LED should be connected to the positive terminal

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16
Q

What happens to the current and potential difference in a diode?

A

As you apply potential difference in the forward direction, very little current flows then it suddenly increases.

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17
Q

What happens when you reverse the potential difference in a diode?

A

There is no current

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18
Q

When would you use a diode?

A

When you want the current to flow in only 1 direction

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19
Q

What is a thermistor?

A

An object in which its resistance depends on temperature

20
Q

What is a thermistor made of?

A

A semiconducting material such as silicon

21
Q

What does a line of constant gradient in a current by PD graph mean?

A

The component is linea

22
Q

What is the gradient of a current by PD graph?

A

Opposite of resistance

23
Q

What does a steep gradient mean in a current by PD graph?

A

Small resistance

24
Q

What does a small gradient mean in a current by PD graph?

A

Large resistance

25
Q

What does a line of changing gradient mean in a current by PD graph?

A

The component is non-linear element

26
Q

What is the resistance of a diode in the reverse direction?

A

Extremely high (infinitely high)

27
Q

How does the resistance of a thermistor change with temperature?

A

As you increase temperature, resistance decreases

28
Q

Why does an increase of temperature mean a decrease of resistance in thermistors?

A

As you heat it, more electrons gain enough energy to escape from the atoms in the semiconductor meaning more electrons become available for conduction

29
Q

What does a thermistor look like in a circuit diagram?

A

A rectangle with a line thorough it which bends outside the rectangle

30
Q

What does an LDR look like in a circuit diagram?

A

A rectangle surrounded by a circle with 2 arrows pointing at it

31
Q

What does LDR stand for?

A

Light-dependent resistor

32
Q

How does a light-dependent resistor work?

A

Its resistance changes with light intensity - as you increase light intensity, resistance decreases

33
Q

Why does an increase of light intensity cause less resistance in an LDR?

A

Light causes more electrons to be released into the circuit, increasing the current

34
Q

How are current and resistance related?

A

As you increase current, resistance decreases

35
Q

What does a resistance graph for a thermistor and LDR look like?

A

Starts high with a curved decrease

36
Q

What would happen if you add another lamp in series?

A

Current decreases
Net resistance increases

37
Q

What happens if you add another lamp in parallel?

A

Total current increases
Net resistance decreases

38
Q

How do you work out net resistance?

A

Potential difference (V)
———————————
Total current (A) - current at end of circuit

39
Q

What is a milliamp?

A

1/1000 A

40
Q

How do you calculate potential difference in a sensing circuit?

A
  1. Calculate net resistance (NR)
  2. Calculate the current (PD of battery over NR)
  3. Calculate PD of what you are looking for (I x R)
41
Q

What is a kilo ohm?

A

1000 ohms

42
Q

What is power?

A

The energy transferred per second

43
Q

How is energy transferred related to potential difference?

A

Potential difference = energy transferred / charge

44
Q

What is the formula for current (in terms of charge)?

A

Charge
————
Time

45
Q

What are the equations for power?

A

Potential difference x current
Current^2 x resistance

46
Q

What is the formula for energy transferred in Joules per Kilowatt Hour (for home appliances)?

A

Power (W) x Time (s)

47
Q

What are the units for power?

A

Warrs

Physics (9 decks)

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