EOY exam

Question 1

what is the weight equation?

Answer 1

weight = mass x gravitational field strength
(N) = (Kg) x (N/Kg)

Question 2

what is the work done and power equation?

Answer 2

work done = force x direction
E = f x d
(J) = (N) x (m)

Question 3

what is the power equation?

Answer 3

power = work done ÷ time taken

Question 4

what is the potential difference equation?

Answer 4

V = I x R
potential difference (volts) = current x resistance
volts = amps x ohms

Question 5

what is the pressure and pressure in a fluid equation?

Answer 5

pressure = force ÷ area
pressure (pascals)

pressure in a liquid = heigh/depth of column x density x gravitational field strength
P = h x ρ x g
pascals = m x kg/m3 x n/kg

Question 6

what is the gravitational potential equation?

Answer 6

GPE = M x G x H
Gravitational potential energy = mass x gravitational field strength x height
(J) = (Kg) x (N/Kg) x (m)

Question 7

what is the kinetic energy equation?

Answer 7

KE = 1/2 x mass x speed 
KE = 1/2 x m x v2 
(J) = 1/2 x (m) x (m/s)

Question 8

what is the specific heat capacity equation?

Answer 8

ΔQ = m x c x Δ ϴ
energy change = mass x specific heat capacity x temperature change
(J) = (Kg) x (J/Kg/degrees) x degrees

Question 9

what is the specific latent heat equation?

Answer 9

Q = M x L
thermal energy = mass x specific latent heat
(J) = (Kg) x (J/Kg)

Question 10

what is the charge equation?

Answer 10

Q = I x T
charge = current x time

Question 11

what is the force on a conductor equation?

Answer 11

F = B x I x L

force x magnetic flux density x current x length

Question 12

what is specific latent heat and specific heat capacity?

Answer 12

SLH: the amount of energy required to change the state of 1Kg of substance

SHC: the amount of energy needed to raise the temperature of 1kg of substance by 1 degree

Question 13

what is current ?

Answer 13

the flow of electrical charge around a circuit. Current will only flow through an electrical component if there is a potential difference across that component and if the circuit is complete.

Question 14

what is potential difference?

Answer 14

(voltage) is the driving force that pushes charge around a circuit
the energy transferred per columb of charge that passes between two points

Question 15

what is resistance?

Answer 15

anything that slows down the flow of charge

Question 16

link potential difference, current and resistance?

Answer 16

the higher the potential difference across a given component, the higher the current will be
the greater the resistance of a component, the smaller the current flowing through it

Question 17

what is the energy transferred equation?

Answer 17

energy transferred = charge moved x potential difference

E = Q x V

Question 18

why does resistance increase with temperature?

Answer 18

when electrical charge flows through a component it has to do work against resistance causing an electrical transfer of energy.
Some of this energy is dissipated to the thermal energy stores of components and the surroundings so when a current flows through a resistor it heats up.
This happens because the electrons collide with the ions in the lattice that make up the resistor as they flow through it giving the ions energy to vibrate and heat up.

The more the ions vibrate, the harder it is for electrons to get through the resistor because there is more collisions. For a given pd the current decreases as the resistor heats up.

Question 19

how can you reduce the amount of energy dissipated to thermal stores as the current flows between components

Answer 19

use low resistance wires

Question 20

explain the energy transfers in a kettle?

Answer 20

electrically from the mains ac supply to the thermal energy store of heating inside the kettle

Question 21

the higher the current…

Answer 21

the more energy is transferred to the thermal energy stores of the components

Question 22

what are the negatives of heating in a circuit?

Answer 22

efficiency reduced because less energy is transferred to useful and more is transferred to it’s thermal energy stores
if temp gets too high the fuse can melt and break the circuit

Question 23

what are the advantages to heating in a circuit?

Answer 23

toasters contain a coil of wire with a high resistance and when a current passes through it its temp increases and it glows red and gives off infrared radiation heating your bread

Question 24

what does power transferred depend on?

Answer 24

pd and current
the pd tells you how much energy each unit of charge transfers
current tells you how much charge passes per unit of charge

Question 25

how do you calculate power if you aren't given the pd?

Answer 25

``` P = I SQUARED X R POWER = CURRENT SQUARED X RESISTANCE ```

Question 26

what is static electricity?

Answer 26

the build up of electrons and charge as a result of friction

Question 27

what charge does a polythene and acetate rod carry?

Answer 27

``` polyethene = - acetate = + ```

Question 28

why will a balloon stick to a wall after you have rubbed it on your hair?

Answer 28

rubbing it on your hair transfers electrons to the balloon leaving it with a negative charge. Then it will stick to a wall because the charges of the surface of the wall can move a little so the negative charges on the balloon repel the negative charges on the surface of the wall leaving a positive charge on the surface of the wall therefore attracting the balloon via attraction by induction

Question 29

what is static electricity in causing sparks

Answer 29

a build up of electric charge on an object means the potential difference between the object and the earth increases . If the pd gets large enough electrons can jump across the gap between the earthed object and the charged this is the spark when object becomes statically charged it generates its own electric field and interactions between this field and other objects cause events like sparking

Question 30

how can you stop electrostatic build up?

Answer 30

by earthing them providing an easy route for the static charges to travel to the safety of the ground

Question 31

what happens when a charged object is placed in a electric field?

Answer 31

it feels a force caused by the electric fields around the two objects interacting

Question 32

what happens between two oppositely charged parallel plates?

Answer 32

a uniform field is created with the strength and direction the same throughout except at the ends

Question 33

what are magnetic materials?

Answer 33

iron nickel cobalt steel

Question 34

what is an induced or temporary magnet?

Answer 34

only produce a magnetic field while they're in another magnetic field this magnetic induction explains why the force between a magnet and a magnetic material is always attractive - the south pole of the magnet induces a north pole in the material and vice versa

Question 35

What happens when you take away the magnetic field of an induced magnet and what does it depend on?

Answer 35

it will lose its magnetism but how quickly depend on... magnetically soft materials like pure iron and nickel alloys lose it quickly magnetically hard materials like steel lose it more slowly

Question 36

what is Flemings left hand thumb rule?

Answer 36

thumb - direction of force (motion) 1st finger - direction of magnetic field 2nd finger - direction of current

Question 37

how do you work out the size of force?

Answer 37

``` F = B x I x L force = magnetic flux density x current x length (N) = (T) x (A) x (m) ```

Question 38

what is magnetic flux density measure in?

Answer 38

tesla (T) or N/Am

Question 39

what is electromagnetic induction?

Answer 39

the induction of a pd and current if there is a complete circuit in a wire which is experiencing a change in magnetic field

Question 40

how can you cause em induction

Answer 40

if a coil of wire (an electrical conductor) and a magnetic filed move close together rotating a coil of wire in a magnetic filed cutting through the field lines when the field size changes

Question 41

how do you increase the size of an induced current ?

Answer 41

add more coils add an iron core move the magnet faster increase field strength

Question 42

what is the moments equation?

Answer 42

moment of force = force x distance | Nm) = (N) x (m

Question 43

what is equal to m x SHC x Δθ

Answer 43

p x t

Question 44

four different ways energy is transferred between stores?

Answer 44

mechanically electrically heating radiation

Question 45

ball rolling up a slope energy transfers?

Answer 45

does work against gravity | energy mechanically from KE store to GPE store

Question 46

bat hitting a ball?

Answer 46

energy from bats KE store to balls KE store | some lost through heat and sound

Question 47

rock dropped from cliff?

Answer 47

from gravity to KE assuming there is no air resistance | gravity does work on the rock so it accelerates

Question 48

car slowing down without breaking

Answer 48

KE transferred mechanically due to friction and then by heating to the thermal energy stores of the car + road

Question 49

a kettle boiling water ?

Answer 49

energy is transferred electrically from mains to the heating element and then by heating to the thermal energy store of the water

Question 50

why do leavers make it easier to do work?

Answer 50

leavers transfer the turning effect of a force to make it easier to do work as they increase the distance from pivot

Question 51

How do you calculate moment?

Answer 51

moment is the turning effect of a force moment = force x distance from pivot

Question 52

what is density and the equation?

Answer 52

density is the relationship between mass and volume ``` density = mass / volume g/cm3 = g / cm3 ```

Question 53

what are the state changes

Answer 53

``` solid -> gas = sublimation gas -> solid = deposition liquid -> gas = evaporation gas -> liquid = condensing solid -> liquid = melting liquid -> solid = freezing ```

Question 54

what is fluid pressure?

Answer 54

fluid pressure if the pressure caused by the collisions of gas or liquid particles on a given surface. fluid pressure increases with depth because there are more particles above

Question 55

what happens when an object is submerged in a fluid?

Answer 55

the pressure of the fluid exerts a force on it in every direction pressure increases with depth so the force exerted on the bottom of the object is larger than the force acting on the top of the object this causes a resultant force called upthrust which is equal to the weight of the fluid that has been displaced by the object

Question 56

when does an object float?

Answer 56

if the upthrust is equal to the objects weight the forces balance out wether or not an object floats depends on its density less dense then fluid it floats

Question 57

why does atmospheric pressure decrease with height ?

Answer 57

as the altitude increases the atmosphere gets less dense so there are fewer air molecules that are able to collide with the surface and there are fewer air molecules above a surface as height increases so the weight of the air above it which contributes to atmospheric pressure decreases with altitude

Question 58

how do we investigate elasticity?

Answer 58

measure natural length of spring when no load is applied with a millimetre ruler clamped to the stand. Add mass to the spring and allow the spring to come to rest. record the mass and then new measurement of the spring. The extension is the change in length repeat this until you have no fewer than 6 measurements plot a force-extension graph . It will only start to curve if you exceed the limit of proportionality a larger force causes bigger extension and more work needs to be done

Question 59

energy transferred in stretching equation?

Answer 59

E = 1/2 x K x X squared energy transferred = 1/2 x spring constant x extension squared (J) = 1/2 x (N/m) x (m squared)

Question 60

what is the motor effect?

Answer 60

when a current carrying conductor is put between two magnetic poles, the two magnetic fields interact causing a force on the wire

Question 61

what are the eight energy stores?

Answer 61

``` kinetic thermal gravitational chemical electrical electrostatic magnetic nuclear ```

Question 62

what happens when a system (groups of objects your interested in) changes?

Answer 62

energy is transferred into or away from the system | some energy is dissipated and stored in less useful ways

Question 63

what happens when a force moves an object?

Answer 63

when a force moves and object through a distance work is done on the object on the object and energy is transferred

Question 64

what is force

Answer 64

a vector when two objects interact they both feel an equal but opposite force - interaction force

Question 65

describe moments on a spanner?

Answer 65

the force on the spanner causes the turning effect or moment of the nut which acts as a pivot.