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Physics > Electrical Circuits > Flashcards

Electrical Circuits Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

The relationship between the cross section of a wire and resistance.

A

The bigger the cross sectional area, the lower the resistance.

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2
Q

What is the main control variable of experiment when testing using a circuit and how do we do this?

A

Important to control the temperature of the wire by turning the power pack off once we’ve gotten the readings.

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3
Q

What is the relationship between the length of a wire and the temperature of the wire?

What is the relationship between the length of a wire and the resistance?

A

As the length increases, so does the temperature.

As the length increases, so does the resistance.

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4
Q

What is a component that obeys Ohms law called?

A

Ohmic

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5
Q

What is ohm’s law?

A

At a constant temperature, the current through the resistor is directly proportional (line goes through the origin) to the potential difference.

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6
Q

Why do components get hot?

A

Components get hotter when there is an electric current flowing through them.

This is caused by lots of collisions between the electrons and the ions held in a fixed lattice (which make up the wire).

Fixed lattice- solid structure.

When collisions occur, energy is transferred from the electrons and to the ions (particles).

The energy which is transferred to the particles causes them to vibrate more.

The temperature increases due to their vibrations.

The more collisions, the more higher the resistance is.

As the heat increases, the ions vibrate more which causes even more collisions to occur.

This causes an even higher resistance in the component and so on.

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7
Q

What is the equation for potential difference which includes:

  • Potential difference
  • Energy
  • Charge
A

Potential difference = energy /charge

Potential difference (v)is measured in volts(v)

Energy (E) is measured in joules (J)

Charge (Q) is measured in coulombs (C)

v = E/Q

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8
Q

What does a potential difference represent?

A

The difference in the amount of energy that charge carriers have between two points in a circuit.

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9
Q

What is potential difference also known as and what is it measured in?

A

Also known as voltage and is measured in volts (v).

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10
Q

To measure the potential difference across a component, where does the voltmeter need to be and why?

A

The voltmeter must be in parallel with the component in order to measure the difference in energy from one side of that component to another.

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11
Q

The Q for Coulombs stands for…

A

…the quantity of elections

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12
Q

Potential difference is…

A

the energy, per unit of charge, transferred between two points in a circuit.

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13
Q

What do all components provide?

A

Resistance

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14
Q

What is potential difference measured by?

A

Volts/ A voltmeter

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15
Q

What does the current through a component depend on?

A

The resistance of that component

The potential difference across the component

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16
Q

Which component measures current?

A

Ammeter

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17
Q

To measure current through a component, where does the ammeter need to be?

A

In series with the component.

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18
Q

With a current of 1.5 amps, and in 60 seconds, ________ coulombs of charge flow a point.

A

Q = It

Q = 1.5 x 60

Q = 90C

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19
Q

Electrical work is done and energy is transferred when…

A

current flows

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20
Q

The equation which has

Charge

Current

Time

A

charge = current × time

Q = It

This is when:

charge (Q) is measured in coulombs (C)

current (I) is measured in amps (A)

time (t) is measured in seconds (s)

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21
Q

In every 1 coulomb there are … electrons.

A

6.25 x 10^18

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22
Q

What is charge measured in?

A

Coulombs

(Q)

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23
Q

What do you call the amount of times the current is altered in AC?

A

Frequency

24
Q

Explain the current in DC.

A

The current is flowing in one direction/ the flow of electrons are consistently in one direction around the circuit.

25
Q

How many types of current are there and what are they?

A

2 types

Direct and Alternating

26
Q

What is resistance measured in?

A

Ohms

(R)

27
Q

What is resistance?

A

Resistance is the restriction of flow of charge (electrons).

28
Q

Explain what a diode does.

A

Allows current to flow in one direction only. They’re used to convert an alternating current into a direct current.

29
Q

Explain what a light-dependent resistor (LDR) does.

A

The resistance of a LDR depends on light intensity.

Low light levels = high resistance

High light levels = low resistance

Can be used as automatic lights when it gets dark.

30
Q

Explain what thermistor does.

A

The resistance of a thermistor depends on its temperature.

Low temperature = high resistance

High temperature = low resistance

31
Q

Explain what a variable resistor does.

A

Moving the position of the slider on this resistor, changes the resistance. The value of the resistance can be changed.

These can be used to dimmer switches and volume controls.

32
Q

Explain what a fixed resistor does.

A

A resistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that cannot be changed.

33
Q

Explain what a lamp does.

A

An electrical current heats the filament in a bulb so that it gives out light.

34
Q

Explain what a switch does.

A

A switch is used to turn a circuit on (closed switch) and off (open switch).

35
Q

Components meaning + example

A

A device in an electric circuit.

E.g, battery, switch, or lamp.

36
Q

Series

What if a component breaks and why?

A

All other components stop working because the circuit is broken and charge can no longer flow.

37
Q

What is the electrical current?

A

The rate of flow of electrical charge

38
Q

Explain the current in AC.

A

The direction of the current is alternating. It constantly changes direction.

39
Q

What transfers energy in wires?

A

Electrons, negatively charged particles, transfer energy through wires as electricity.

40
Q

Series

How many paths for current to flow?

A

1

41
Q

V =?

A

V= IR

42
Q

Series
If one ammeter showed a current of 3A, what would the one next to the filament lamp show?

A

3A
Current is the same everywhere in a circuit.

43
Q

Series
How do you work out the total potential difference of the circuit?

A

V (total) = V (1) + V (2) + V (3)
The potential difference is shared across all the components.

44
Q

Series
Components with greater resistance have a higher…

A

… share of the voltage.

45
Q

Series
What is the equation for resistance (total) in a circuit?

A

R (total) = r (1) + r(2) + r (3)

46
Q

Series
When connecting a voltmeter, how should it be added and why?

A

In parallel to the component we’re measuring to measure the energy across the component.

47
Q

Parallel
If Senku used a battery of 12 v in a circuit, how many volts would a filament lamp in the circuit have?

A

12v
V (total) = V (1) = V (2) = V (3)

48
Q

Parallel
If the total current of Senku’s circuit was 12A, and there were two loops with one loop containing 8A, what would the other loop’s current be?

A

4A
Current is shared between all components
A (total) = A (1) +A (2) +A(3)

49
Q

Parallel
Loops with greater resistance will have more current.
True or false?

A

False
The current will take the path with the least resistance and the current splits depending on the resistance of the individual component.

50
Q

Parallel
What is the rule for resistance, why is it like this?

A

< the smallest resistor
The more components we add, the lower the total resistance because the current has more paths to flow and it will take less force (the multiple paths decreases the overall potential difference ).

51
Q

Why does a filament graph (measuring it’s current, as potential difference increases) curve off at the end?

A

As the current increases, the temperature of the filament in the lamp increases
The higher temperature causes the atoms in the metal lattice of the filament to vibrate more
This causes an increase in resistance as it becomes more difficult for free electrons (the current) to pass through
Therefore, more potential difference is needed to transfer the same amount of current.

52
Q

What is a filament lamp an example of?

A

A non-ohmic conductor

53
Q

As the graph for a filament lamp curves, what happens to the resistance?

A

The resistance increases as the graph curves.

54
Q

What is constant when the line of a graph (of the current against the potential difference) is straight?

A

Resistance is constant.
Temperature is also constant.

55
Q

What shows that the conductor is non-ohmic?

A

They have a resistance that varies with the conductors.

56
Q

What does current depend on in a circuit?

A
  • Potential Difference
  • Resistance
57
Q

Current
Potential difference
Resistance

A

V = IR

V = potential difference
I = current
R = resistance

Physics (3 decks)

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