Physics (Jones) Flashcards by David Williamson

What are the different base unit quantities and what they are measured in

Mass (Kg)
Length (M)
Time (S)
Electrical current (A)
Tempureture (K)
Amount of substance (mol)

METAL

How well did you know this?

Not at all

Perfectly

What are the prefixes and there ^ to 10 and there symbols

Peta (P) 10^15
Tera (T)10^12
Giga (G) 10^9
Mega (M) 10^6
Kilo (K) 10^3
Deci (d) 10^-1
Centi (c) 10^-2
Milli (m)10^-3
Micro (u) 10^-6
Nano (n) 10^-9
Pico (p) 10^-12
Feunto (f) 10^-15

How well did you know this?

Not at all

Perfectly

What are the base measurements and there units

Kilograms (Kg)
Kelvin( K)
Amperes (A)
Metre (M)
Moles (mol)
Candela (cd)
Seconds (s)
MACKS

How well did you know this?

Not at all

Perfectly

Homogeneity definition

Where an equation has the same base units on both sides of the equals

How well did you know this?

Not at all

Perfectly

Definition of error

The difference between the result and real value

How well did you know this?

Not at all

Perfectly

What are the 2 types of error and what are there properties

Radom - always humans fault (parellex error)
Systematic - differs the same amount each time for an incorrect results

How well did you know this?

Not at all

Perfectly

Definition of random error and type of error

It’s a humans fault
Type:
Parallax error

How well did you know this?

Not at all

Perfectly

Definition of a systematic error and type

The result differs by the same amount each time for am incorrect result
(Zero) error

How well did you know this?

Not at all

Perfectly

Definition of Resolution

The lowest increment of measurement

How well did you know this?

Not at all

Perfectly

What is absolute uncertainty

If we only have one measurement the absolute uncertainty = resolution

If we have multiple measurements the absolute uncertainty = range\2

How well did you know this?

Not at all

Perfectly

Percentage uncertainty equation

Uncertainty/mean * 100
The value we give and the absolute uncertainty must have the same number of decimal places

How well did you know this?

Not at all

Perfectly

What is combined uncertainty

Absolute uncertainty 1 + absolute uncertainty 2

How well did you know this?

Not at all

Perfectly

Rules of combined uncertainties

If quantities are added or subtracted we always add the uncertainties together

How well did you know this?

Not at all

Perfectly

What do we do if we are multiply or dividing uncertainties

We add the percentage uncertainty of the quantities to calculate the uncertainties we want

How well did you know this?

Not at all

Perfectly

What is current

Rate of flow of charged particles
If its metals it will be electrons

How well did you know this?

Not at all

Perfectly

What is the equation that links current to change and the units

Q=It
Current (a)=
Charge(c)/time(s)

How well did you know this?

Not at all

Perfectly

Quantisation of charge equation and what each letter stands for

Q=ne
N is number of electrons/ protons
E is elemental charge
Q is charge

How well did you know this?

Not at all

Perfectly

What is elemental charge

1.6x10^-19

How well did you know this?

Not at all

Perfectly

What direction does conventional current go

Positive to negative

How well did you know this?

Not at all

Perfectly

What direction do electrons flow

Negative to positive

How well did you know this?

Not at all

Perfectly

When we have a circuit going into the solution what moves

The ions move

How well did you know this?

Not at all

Perfectly

What is Kirchhoffs first law

{current(I) in = {current(I) out
Sum of currents in junction are equal to sum of the current out the junction
This is true because of conservation of charge

How well did you know this?

Not at all

Perfectly

What happens to the particles in a wire with no charge going through them

They vibrate around a fix point
Free electrons can’t move in the wire so no overall movement

How well did you know this?

Not at all

Perfectly

What happens to the particles in a wire if a charge is flowing through them

If we plug a wire into a circuit - apply a potential difference across the wire then the free electrons move along the wire
And there is net movement overall
There is displacement along the wire

How well did you know this?

Not at all

Perfectly

What is another equation for current that isn’t Q=IT

I = nAVe I= current(A) n= number density (m^3) [cm^-3] e=elemental charge (C) V = mean drift velocity

What is the number density for a conductor and what are two conductors

X10^28 m^-3 Copper Zinc

What is the number density of a semiconductor

X10^15 - x10^q8 Silicon Germanium

What is the number density for an insulator

Polyethylene Wood 0m^-3 - 100m^-3

What is potential difference

The energy gained or transferred by charge carrier

What is the equation for potential difference

Potential difference(volt) = energy gained(joules) / charge(coulombs) V(V) = E(J) / Q(C) Potential difference = work done / charge V = W/Q

What is 1 amp equivalente to and 1 volt equivalent to

1 amp = 1 coulomb per second 1 volt = 1 joule per coulomb 1V = 1JC^-1

What happens in a battery

Work is done at the charges Charge gaining energy as it transfers from chemical energy to electrical energy Potential difference of a cell battery is called emf (electromotive force) When work is done by the charges

What happens in an electron gun

Electrons gain energy They accelerate Therefore velocity increases

What is ohms law

V = IK At a fixed temperature V = I Resistance = R

How would you write an I-V characteristic 6 marker

Measures the current(I) with the ammeter Measure the potential difference P.D (V) with the Volt meter Calculate resistance with R=V/I Increase p.d on the variable power supply Repeat steps 1-4 Switch wires on power supply two get negative values Repeat steps 1-5

What are properties in a circuit with a filament lamp in it

V increases + I increases but by less per volt at higher currents because resistance increase Temperature increases Ions vibrate with greater amplitude and greater frequency causing more collisions with free electrons

What are properties of a circuit with a diode in it

PD is negative the current is 0 amps as resistance is infinite PD is positive the current remains at 0-1A until threshold voltage The resistance decreases so the current increases the n(number density per m^3) Value increases

What are characteristics of a thermistor

There is a negative temperature coefficient As temperature increases Resistance decreases

What are characteristics of a LDR

Negative coefficient of light intensity Light intensity increases Resistance decreases

Why does light intensity and temperature have a negative coefficient

Thermistors and LDRs work by as temp or light increase they release more free electrons So a greater current can flow at resistance decrease Increase the ‘n’ value N = number of charge carriers

What does resistance depend on

Length and area

What is equation for the proportions of area and length

R= L/A

Equation that links resistivity and resistance

R = xL/A

What happens to potential difference in a series circuit

P.d splits

What happens to potential difference in a parallel circuit

Potential difference is the same in every branch of a parellel circuit

What is the equation that links potential difference energy and charge

V = E/Q

What happens to current in series

Current stays the same

What happens to current in parallel

It is split along the branches

What is the equation for resistance in a series circuit

V=IR

What is the equation for resistance in parellel

1/R + 1/r2 + 1/r3 = 1/Rt

What is emf

The work done on charges Energy gained per unit charge

What is voltage equal in a system with internal resistance

V = terminal p.d The potential difference measured across terminal of a cell when a circuit has a current through T it

What is Ir equal to

It is the work done by charges travelling through out the cell P.d the internal resistance

What is the p.d across the internal resistance also called

Lost volts - potential difference across the internal resistance of the cell

What is emf equal to

Terminal p.d + lost volts

What is the definition of voltage

Work done by the charges

What is the internal resistance

Resistance of Source of emf

What does the internal resistance cause

Some energy to be transferred as thermal energy

What do volt meters read when there is internal resistance

Terminal pd - the amount of energy used to leave the battery

What happens to p.d when no current is flowing through a circuit

No volts are lost so emf=V

What happens to p.d as current increases

P.d decreases because more volts are lost

What is Kirchhoff second law

In any closed loop of a circuit Sum of emf = sum of p.d

How is p.d distributed in a circuit

In the same ratio as resistance

What is the equation for potential dividers

V1/V2 = R1/R2

What is v out equal to

V out = R2/R1 +R2 x V in

What is total resistance equal to

R1 + R2 = R total

What is total p.d equal to

V total = V1 + V2

What does potentiometer do

Controls voltage in a circuit

Physics (Jones) Flashcards

(68 cards)