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5.Electricity - A levels Physics > 5.1 - Current-Voltage Characteristics > Flashcards

5.1 - Current-Voltage Characteristics Flashcards

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1
Q

What is electric current?

A

The rate of flow of positive charge.

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2
Q

What is current measured in?

A

Amperes (A) or amps

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3
Q

What the equation to work out current?

A

I =ΔQ/Δt
I = current
ΔQ = change in charge
Δt = change in time

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4
Q

What is charge?

A

A property of some particles that results in them being either attracted or repelled by other charged particles.

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5
Q

What is charge measured in?

A

Coulombs (C).

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6
Q

What is potential difference (voltage)?

A

The work done (energy converted) per unit charge moved.

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7
Q

What is an ammeter?

A

A component of a circuit that measures the current flowing through a part of a circuit.

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8
Q

What is the equation to find potential difference?

A

V = W/Q
V = voltage / potential difference (V)
W = work done (J)
Q = charge (C)

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9
Q

What is a voltmeter?

A

A component of a circuit that measures the potential difference.

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10
Q

What is the definition of a volt?

A

The potential difference across a component is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component. (1V = 1JC⁻¹)

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11
Q

What is conventional current defined as?

A

The flow of positive charge from the positive terminal of a cell to the negative terminal. (conventional current always + –> -, electron flow opposite)

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12
Q

How should ammeters always be connected to a circuit?

A

In series.

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13
Q

How should voltmeters always be connected to a circuit?

A

In parallel.

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14
Q

What is 1 volt equivalent to?

A

1 volt = 1JC⁻¹

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15
Q

What is resistance?

A

The opposition to current.

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16
Q

What is the relationship between p.d, resistance and current?

A

For a given p.d: the higher the resistance, the lower the current.

17
Q

What is the equation to find resistance?

A

R = V/I
R = resistance
V = p.d
I = current

18
Q

What is resistance measured in?

A

Ohms (Ω).

19
Q

What are ohms defined as?

A

One volt per ampere.

20
Q

What is Ohm’s law?

A

For a conductor at a constant temperature, the current through it is proportional to the potential difference across it.
(V=IR)

21
Q

What is the graph for plotting current against potential difference through a fixed resistor?

A

A straight line graph going through the origin.

22
Q

What is the graph for plotting current against potential difference through a fixed resistor?

A

A straight line graph.
(Gradient = 1/R)

23
Q

What is a component that obeys Ohm’s law?

A

A resistor.

24
Q

What is a material that doesn’t obey Ohm’s law?

A

A filament bulb.

25
Q

What do IV graphs show?

A

How current flowing through a component changes as the potential difference across it is increased.

26
Q

What do IV graphs of ohmic conductors look like?

A

Straight line graph. A steeper gradient means a low resistance (vice versa).

27
Q

What does the IV graph of a filament lamp look like?

A

An S shape curve (starts steep and gets shallower as the voltage rises).

28
Q

What does the IV graph of a semiconductor diode?

A

A horizontal line that goes sharply upwards at the end.

29
Q

How good are semiconductors at conducting electricity and why?

A

No where near as good as metals because there are far fewer charge carriers available.

30
Q

What are semiconductors useful for?

A

They are very good sensors for detecting changes in their environment.

31
Q

What are the 2 semiconductors that we look at in this specification?

A

Semiconductor diodes and thermistors.

32
Q

What is a semiconductor diode used for?

A

Used in a circuit to allow current to flow only in a specific direction.
Forward bias - when current is in the direction of the arrowhead symbol. (Sharp increase in p.d)
Reverse bias - switched around, does not conduct (0 p.d and I on the left side of the graph).

33
Q

Why does the IV graph of a filament lamp look like it does?

A

As current increases, temp increases.
Filament is a metal, so increase in resistance.
Resistance opposes the current, current increases at a slower rate.

5.Electricity - A levels Physics (4 decks)

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