Edexcel IGCSE Physics Full Course

How do you calculate the speed from a distance-time graph ?

the speed/velocity is the gradient

State the equation for average speed

average speed = distance travelled /time taken

v[m/s]=s[m]/t[s]

Practical: investigate the motion of everyday objects such as toy cars or tennis balls

state the equation for acceleration ( using velocity and time)

acceleration = change in velocity / time taken

a[m/s/s] = (v-u)[m/s]/t[s]

How do you calculate the distance from a velocity time graph?

The distance is the area under the graph

How do you calculate the acceleration from a velocity time graph?

The acceleration is the gradient of the graph

State the equation for final speed

final speed squared [m/s] = initial speed squared [m/s] + 2 x acceleration[m/s/s] x speed [m/s]

What are the effects of a force?

1. can change the speed of an object
2. can change direction an object is travelling in/ can rotate an object
3. can change shape of an object

List the different types of forces:

1. Gravity/Weight
2. Reaction Force
3. Electrostatic Force
4. Thrust
5. Drag/Air Resistance
6. Friction
7. Lift
8. Tension
9. Magnetic
10. Nuclear

What is the difference between a vector quantity and a scalar quantity?

a scalar quantity only has magnitude (size) whereas a vector quantity has magnitude(size) and direction

How do you calculate the resultant force of forces acting on a line ?

you add up the forces in each direction

You subtract the larger force from the smaller force, to get the resultant force

The resultant force acts in the direction of the larger force

What is friction ?

a force that opposes motion

State the equation for force (using mass and acceleration)

force = mass x acceleration

F[N] = m[Kg] x a[m/s/s]

State the equation for weight

Weight (N) = mass (kg) x gravitational field strength (N/kg)

W[N]=m[Kg] x g[m/s/s]

What is stopping distance and how do you calculate it ?

the distance a vehicle travels from the second a hazard is detected till the car stops

stopping distance = thinking distance + braking distance

What factors affect stopping distance?

speed
mass
road condition
reaction time

Describe the forces acting on a falling object

*CHECK

1. initially v=0 and drag=0 , only weight acting on it

2. Then as it falls it will experience drag , however initially the weight force is higher

3. the object will begin to move faster towards the ground, simultaneously the force of drag increases

4. the weight and drag forces balance out so there is no resultant force on the object and it reaches(constant) terminal velocity

Practical: Investigate how extension varies with applied force for helical springs, metal wires and rubber bands

What is Hooke's law?

The extension of a spring is directly proportional to the force applied up until the limit of proportionality

Define the term elastic behaviour

the ability of a material to recover its original shape after the forces causing deformation have been removed

State the equation for momentum

momentum = mass x velocity

p[kgm/s]=m[kg] x v[m/s]

Explain how safety features in a car work , with respect to momentum

Airbags&Seatbelts

1. Absorbs energy from the impact, 2.increases time taken for the force to act on the passenger

3. Since force = change in momentum/ time taken , and time increases = the force decreases

Crumple Zones

1. part of the car which collapses during a collision

2. Increases time during which the car is decelerating

3. And since force = change in momentum / time , and if time increases force felt on the passenger decreases

State the principle of conservation of momentum

momentum before collision = momentum after collision

total initial momentum = total final momentum in an elastic reaction

elastic reaction , a reaction where initial KE = final KE

State the relationship between force and momentum

force = change in momentum / time taken

F[N] = (mv-mu)[kgm/s]/t[s]

Explain Newton's third law

if object A exerts a force on object B then object B exerts an equal and opposite force on object A

State the equation for a moment

moment = force x perpendicular distance

m[Nm] = F[N] x d [m]

Where does weight act on a body?

through the centre of gravity (the centre of the object)

How do you calculate the moment for parallel forces acting in one plane?

you use the moment formula and calculate the distance from the pivot of both of the forces

You then subtract the smaller moment from the larger moment to give the total moment which is in the direction of the larger moment

You may use:
F1 x d1 = F2 x d2
Then rearrange if asked to find a particular force or distance

Describe how the upward forces on a light beam supported at its ends vary with position of a heavy object placed on the beam

If a beam is supported at ends A and B

(take centre as pivot )

As the mass moves towards A :
Upwards Force on A increases
Upwards force on B decreases

As the mass moves towards B:
Upwards force on A decreases
Upwards force on B increases


This is because the CW moment must equal the ACW moment to secure the beam

What is insulation in domestic appliances ?

1. insulation in a plug is when the live, neutral and earth wires are covered with a plastic layer

2. plastic is a good insulator

3. this prevents contact with the live wire when handling the plug and prevents the person receiving a large current

What is double insulation in domestic appliances?

1. double insulation is when the casing of the plug is made of plastic and wires are covered in plastic casing

2. this means that even if the live wire breaks and touches the outer casing a charge cannot go through

3. as plastic is a good insulator

4. preventing any risk of electric shock as well as reducing the need for an earth wire

What is earthing in domestic appliances?

1. earth connected to (metal) casing;

2. If casing becomes live/ live wire touches case;

2b. absorbs electrons

3. Provides low resistance path (to earth);

4. (So) large/surge current in earth wire;

5. (hence) fuse breaks/melts/blows;

6. (so) circuit switches off

What are fuses ?

1. a thin piece of metal with a low melting point

2. if there is a current which is too large, the fuse heats up and becomes very hot and melts/breaks

3. breaking the circuit and preventing the large current from flowing

4. preventing the risk of electrical fire and severe electrical shock

What are circuit breakers?

1. A circuit breaker has a coil or a metallic strip which detects the amount of current lowing through a circuit

2. When the current goes above the acceptable range the current sensing system detects it and causes the circuit breaker contacts to open

3.Breaking the circuit preventing the large current from flowing , preventing electrical fires and risk of electrical shock

4.After the fault is checked the circuit breaker can be reset and some do this on their own, meaning a circuit breaker can be re-used

5.This makes it better to use than a fuse, however they are more expensive than fuses

How do resistors heat up and how can this be used in domestic appliances?

1. when resistors are applied current is reduced and the rate of flow of electrons slows down

2. this means that there is more collision of electrons and ions in the resistor

3. this means there are more transfers of electrical energy into heat energy in the resistor

P= I x I x R so higher R is more power dissipated as heat

State the relationship between power , current and voltage

Power[W] = current [A] x voltage [v]

P = I x V

State the relationship between energy transferred, current, voltage and time

Energy Transferred [J] = Current [A] x Voltage [v] x Time [s]

E = I x V x t

What is the difference between alternating current and direct current ?

1. Alternating current is supplied by mains electricity
Direct current is supplied by a cell or battery

2. Alternating current changes direction , Direct current travels in one direction

3. Alternating current can vary in size , Direct current remains at one size

Which is better suited for domestic lighting series or parallel circuits , and why ?

1. A parallel circuit is better suited

2. because if there is a fault in one of the branches it will not effect the others

3. whereas in a series circuit if there is a fault in any part the whole circuit stops working

What factors affect current in a series circuit ?

Voltage:
the higher the voltage the higher the current (I=V/R)

Number of components :
The higher the number of components the lower the current as the overall resistance increases and voltage has to be split up further resulting in a lower current

Nature of components:
components with a higher resistance will reduce current as I=V/R

Describe the IV characteristics of a. wire

Describe the IV characteristics of a resistor

Describe the IV characteristics of a filament lamp

Describe the IV characteristics of a diode

How do you test the IV characteristics of a component?

What is the effect of changing resistance on the current in a circuit?

increasing the resistance in a circuit reduces the amount of current which flows through the circuit

(so we use resistors to limit current, e.g. before lamps)

How does a LDR work ?

How does a thermistor work ?

State the formula for voltage , current and resistance

Voltage [V] = Current [A] x Resistance [Ohms]

V=I x R

Define the term current

current is the rate of flow of charge(/electrons)

State the formula for charge, current and time

Charge [C] = Current [A] x time [s]

Q = I x t

Define the term electric current

electric current in solid metallic conductors is the flow of negatively charged electrons

Why is current conserved at a junction in a circuit ?

this is because the current entering a junction = the current exiting a junction

Describe the voltage in a parallel circuit ?

The voltage across two components connected in parallel is the same

How do you calculate the current, voltage and resistance of two components connected in series ?

the current through both components is the same

To calculate voltage :
1. use V=IR to find voltage over one component

2. subtract voltage from power supply to find voltage over other component


To calculate resistance:

1. use V=IR to find voltage over one component

2. subtract voltage from power supply to find voltage over other component

3. Use R = V/I to find resistance of second component

Define the term voltage

voltage is energy transferred per unit charge passed

What is a volt

a volt is a measure of joule transferred per coulomb

State the relationship between energy transferred, charge and voltage

Energy transferred [J] = Charge [C] x Voltage [V]

E = Q x V

Which common materials are electrical insulators ?

a material that doesn't allow electricity to flow through easily

examples :
plastic
rubber
glass
wood

Which common materials are electrical conductors?

A conductor is a material that allows electricity to flow through it easily

Examples:
Graphite
Copper
Tin
Gold

Practical: Investigate how insulating materials can be charged by friction

How are positive and negative electrostatic charges produced on materials ?

1. when you rub two neutral insulators together

2. the friction causes one of the materials to take electrons from the other

3. the material which loses electrons becomes positively charged

4. the material that gains electrons becomes negatively charged

State the law of electrostatics

Like charges repel and unlike charges attract

Explain an electrostatic phenomena?

Lightning:

1. rubbing of air and dust particles causes some negatively charged particles at the bottom of clouds

2. these negative charges repel electrons in the ground leaving a positive charge near the top of the ground

3. the difference in charge becomes too large and a potential difference which drives a current between the cloud and the ground is created

4. current heats the air till it begins to glow as a flash of lightning

5. (due to the quick heating ) the air also expands rapidly creating the sound of thunder

What are the dangers of electrostatic charges when fuelling aircrafts and tankers ?

1. Planes travel through air and clouds

2. friction between the plane, air and dust particles causes the plane to become charged with static electricity

3. when the plane lands the charge could escape to earth as a spark or flash

4. however if someone is trying to refuel the plane during this a spark could occur and cause an explosion

How can electrostatic charges be used in photocopiers ?

How can electrostatic charges be used in inkjet printers?

What is the difference between longitudinal and transverse waves ?

longitudinal waves vibrate parallel to the direction the wave travels

Transverse waves vibrate perpendicular to the direction the wave travels

Define the term amplitude

the maximum distance moved by a vibrating object from its equilibrium position

Define the term wavefront

an imaginary surface which shows the position of particles at different phases of the wave, it is made by overlapping lots of different waves

a wavefront is a line where all the vibrations are in phase and the same distance from the source

Define the term frequency

the number of waves passing a point per second

Define the term wavelength

the distance from one point on a wave to the corresponding point on the next wave

Define the term time period

the time needed to make one complete wave or vibration, measured in seconds

What is a wave?

(a disturbance) that transfers energy and information without transferring matter

State the relationship between speed, frequency and wavelength

Wave Speed = Frequency x Wavelength

v = f × λ

State the relationship between frequency and time period

Frequency = 1 / Time Period

f = 1/T

What is the doppler effect ?

the change in frequency caused by the relative movement of the source of the waves or the observer


( wavefronts squash or stretch, changing wavelength and frequency )

What are some similarities between all waves ?

all waves can be reflected and refracted

all waves transfer energy and information without transferring matter

What spectrum is light in ?

Electromagnetic Spectrum

What properties are shared by EM waves?

all EM waves travel at the same speed in free space

State the order of the EM spectrum in terms of decreasing wavelength ?

radio waves
microwaves
infrared
visible light
ultraviolet
x-rays
gamma rays

State the order of the EM spectrum in terms of increasing frequency ?

radio waves
microwaves
infrared
visible light
ultraviolet
x-rays
gamma rays

What are the uses of radio waves?

broadcasting and communications

What are the uses of microwaves?

cooking and satellite transmissions

What are the uses of infrared waves?

heaters and night-vision equipment

What are the uses of visible light ?

optical fibres and photography

What are the uses of ultraviolet ?

fluorescent lamps

What are the uses of x-rays ?

Observing the internal structure of objects and materials and medical applications (medical imaging and treatments)

What are the uses of gamma rays?

Sterilising food and medical equipment

What are the dangers of microwaves and how can we prevent this?

internal heating of body tissue

Microwave ovens have a metal grill over the door which reflects back microwaves into the oven to protect users

What are the dangers of infrared waves and how can we prevent this?

skin burns

take care when using sources of infrared waves, e.g. move heater away from body

What are the dangers of ultraviolet waves and how can we prevent this?

damage to surface cells ( sunburn) blindness

wear sun-cream, stay in shade

wear UV absorbing sunglasses

don't use tanning beds for too long

What are the dangers of gamma rays and how can we prevent this?

can cause cancer and cell mutations

wear photographic film badges , if they turn dark when developed a person has too much radiation and must stop working/ being around them

What are the properties of light waves?

transverse waves that can be reflected and refracted

How do you use the law of reflection ?

the law of reflection states that the angle of incidence = the angle of reflection

so when given one of these angles you can find the other

How do you draw ray diagrams of reflection and refraction ?

you draw arrows in the direction which light travels

whenever light changes direction/ goes through a material draw a normal at 90 degrees

Practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms

state the relationship between , refractive index, angle of incidence and angle of refraction

refractive index = (sin angle of incidence ) / (sin angle of refraction)

Practical: investigate the refractive index of glass, using a glass block

How can total internal reflection be used to transmit information in optical fibres and prisms ?

thin glass fibres are bent so that the angle of incidence is greater than the critical angle

so when light his the fibre TIR will occur and no light will be refracted until it reaches the end of the optical fibre