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A Level Physics Paper 1 > Electric Circuits > Flashcards

Electric Circuits Flashcards

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1
Q

Define current

A

Rate of flow of charge

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2
Q

What does the gradient on a charge-time graph tell us?

A

Current
I = Q/t

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3
Q

How to you work out charge from a current-time graph?

A

The area under the graph
Q= It

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4
Q

An ammeter must…

A

have a low resistance and must be placed in series

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5
Q

A voltmeter must…

A

have infinitely high resistance and must be placed in parallel

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6
Q

Another word for voltage is…

A

EMF/potential difference

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7
Q

Potential difference is…

A

A measure of the amount of energy or unit of charge transferred between 2 points in a circuit

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8
Q

What is Kirchoff’s first law?

A

The total current flowing into a point is equal to the current flowing out of a point.
Conservation of Charge

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9
Q

What is Kirchoff’s second law?

A

Around any closed loop in a circuit, the sum of the p.d across all components is the p.d of the supply.
Conservation of Energy

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10
Q

Define power

A

The rate of work done

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11
Q

1 watt of power means…

A

1 joule of energy is used every second

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12
Q

State Ohm’s Law

A

V = IR
at a constant temperature

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13
Q

In a series circuit the current is…

A

the same across all components

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14
Q

In a parallel circuit the current is…

A

Total current = the sum of the current in all branches

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15
Q

Potential difference in a series circuit…

A

total p.d is split up across all components, in the ratio of their resistance

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16
Q

Potential difference in a parallel circuit is…

A

the same across each brach
p.d across each branch = p.d of source

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17
Q

Resistance in a series circuit…

A

total resistance = the sum of the resistance in all the components

18
Q

Resistance in a parallel circuit…

A

Reciprocal of Resistance = the same of all the reciprocals of the resistance of all the components
1/RT = 1/R1 + 1/R2 + 1/R3 …

19
Q

Is a resistor a conductor?

A

Yes - it is a conductor so current can still flow around a circuit however resists let less current flow

20
Q

What effects the resistance of a resistor?

A

CSA of the wire
Length of the wire
Material of the wire (resistivity)
Temperature of the wire

21
Q

What is resistance proportional to?

A

Length

22
Q

What is resistance inversely proportional to?

A

CSA

23
Q

What is the Resistivity of a material?

A

The resistance of a 1m^2 long sample (the resistance per unit cube)
It is a property of a material

24
Q

The resistivity is constant if…

A

the temperature is constant

25
Q

What is the conductivity?

A

1/resistivity

26
Q

On a resistance-length graph, what pattern does the graph follow?

A

positive straight gradient

27
Q

On a resistance-length graph, what does the gradient tell you?

A

resistivity/area

28
Q

What does a resistance-area graph look like?

A

A curve getting less steep as it goes down (negative gradient)

29
Q

What does a resistance-1/CSA graph look like?

A

Positive straight gradient

30
Q

What does the gradient of a resistance-1/CSA graph mean?

A

It is the resistivity multiplied by the length

31
Q

Prove:
1/RT = 1/R1+ 1/R2 + 1/R3 in parallel

A

iTotal = i1 + i2 + i3
i = V/R hence:
v/RT = v/R1 + v/R2 + v/R3
v is constant and therefore:
1/RT = 1/R1 + 1/R2+ 1/R3

32
Q

What is a potentiometer?

A

A device that provides a p.d ranging from 0v and Vs (supply voltage)

33
Q

Length needed =

A

length of wire x (voltage out/total voltage)

34
Q

What do the letters stand for in I = nAvq

A

I = Current (A)
v = Drift velocity (ms-1)
A = CSA of conductor (m2)
n = Charge density (no. of electrons per m3)
q = charge on each charge carrier

35
Q

What is the charge density?

A

the number of charge carriers per m3

36
Q

A poor conductor has ___ charge carriers

A

few

37
Q

A good conductor has ___ charge carriers

A

many

38
Q

4V is equivalent to 4J per…

A

coulomb of charge

39
Q

5ohm resistance means that 5v is required for…

A

1A of current

40
Q

Vout/Vsupply =

A

R2 / (R1+R2)

A Level Physics Paper 1 (6 decks)

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