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Physics > 2. Circuits > Flashcards

2. Circuits Flashcards

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1
Q

Definition of current

A

The rate of flow of charge

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2
Q

Current Units

A

Amps

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3
Q

Current equation

A

I = Q / T

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4
Q

Unit for charge

A

Coulombs

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5
Q

What equation do you use to figure out the speed of electrons in a conductor?

A

I = naVe

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6
Q

What does drift velocity mean

A

How fast each electron moves

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7
Q

What does the n stand for in I= naVe

A

Charge carrier density = number of electrons per meter

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8
Q

How to derive I = naVe

A

time = length / velocity
N = volume x charge carrier density
Charge of an electron = e

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9
Q

Definition of potential difference

A

The energy supplied per unit charge

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10
Q

Unit of Pd

A

Volts

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11
Q

Equation to find voltage

A

V = IR or V = E / Q

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12
Q

Definition of resistance

A

The ratio of potential difference to current

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13
Q

Equation for resistance

A

R = V /I

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14
Q

How does resistance occur

A

The collisions between free electrons and the ions means it is harder for electrons to flow

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15
Q

What happens when temp is increased within a conductor

A

Resistance increases as it is proportional to temperature
The kinetic energy of particles increases so particles are moving faster so they collide more therefore higher resistance and temp

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16
Q

What is ohms law

A

R is constant for all values of V and I

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17
Q

What is the equation for resisitivity

A

Resistance = (Resistivity x length) / area

18
Q

What is resistivity

A

The general measurement of how much a material resists the flow of current
It stays constant for the same type of material

19
Q

What is the unit for resistivity

A

Ohm - metre

20
Q

What is the IV graph for a filament lamp

A

Curved starting from the origin

21
Q

What is the IV graph for a metal wire at a constant temp

A

Directly proportional

22
Q

What is power

A

The amount of energy transferred per unit of time

23
Q

Power equation

A

P = IV or P = E/ T

24
Q

What is superconductivity

A

When a material conducts with zero resistance

25
Q

What is the transitional temperature

A

The temperature which a super conductor needs to be cooled down to

26
Q

How are superconductors used

A

Used to create magnets used in trains
MRI scanners
Particle accelerators

27
Q

What quantities are equal across branches in a parallel circuit

A

Potential difference

28
Q

What happens to current in a parallel circuit

A

Each branch must add up to the current through the source

29
Q

What is the difference between sum of resistance in a series circuit and in a parallel circuit

A

Series= resistors all add up
Parallel= Reciprocal of the sum of reciprocals

30
Q

What is a potential divider

A

When there are two resistors in series

31
Q

What is a potential divider used for

A

To supply a variable voltage to an external circuit

32
Q

What is a thermistor

A

A temperature sensitive device that reduces resistance when heated

33
Q

What is an LDR

A

Light dependent resistor
Made out semi conductor material they have a lower resistance when exposed to the lighyt

34
Q

What happens when light intensity increases on a circuit with a LDR

A

The resistance of the LDR decreases so the potential difference also decreases

35
Q

What is EMF

A

Electromotive force

36
Q

Definition of emf

A

The energy supplied per unit charge from the source

37
Q

What is the equation with EMF

A

V = E - Ir

38
Q

What do you do when a series circuit has multiple cells

A

Add up all the emf and add up the internal resistance to make overall total of one cell

39
Q

What is a diode

A

A component that only allows current to flow in one direction

40
Q

What is Kirchoffs first law

A

All of the current going to a junction is equal to the total current leaving the junction

41
Q

What is Kirchoffs second law

A

The sum of potential differences must equal the total emf of the circuit

42
Q
A

Physics (16 decks)

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