Uncategorized

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

when moments are taken from the right hand side as the block is a greater distance the force from the left hand pivot must be bigger to counteract it. The opposite is true for the left hand side. 

2.02 understand how the use of insulation, double insulation, earthing, fuses and circuit breakers protects the device or user in a range of domestic appliances

Fuses Stop the flow of current by melting if the current is too high. So protecting sensitive components and people because if the components function at too higher temperature it can cause a fire. 

Circuit breakers again break the circuit if current is too high. 

Insulation and double insulation prevent people from touching exposed wires and getting shocks.

Earthing provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.  

2.03 understand why a current in a resistor results in the electral transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts

Resistance causes transfer of electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens, for example electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced.

2.04 know and use the relationship between power, current and voltage: and apply the relationship to the selection of appropriate fuses

power (w) = current (A) x voltage (V) 

when looking at a circuit a component will be given a power and a voltage appropriate to run at then the current can be calculated so the rating of the fuse can be selected for slightly higher than that. 

 

2.06 know the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery

AC is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.

DC is constant. And is produced from a battery and used in some sensitive components like in computing.

2.07 explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting

Advantages of parallel circuits:

  • Components (e.g. bulbs) may be switched on/off independently.
  • If one component breaks, current can still flow through the other parts of the circuit.
  • Bulbs maintain a similar brightness.

Advantages of series circuits:

  • Fewer wires, cheaper and easier to assemble.
  • Uses less power

 

 

2.08 understand how the current in a series circuit depends on the applied voltage and the number and nature of other components

Notes on current:

  • As voltage increases the current also increases.
  • In general, the more components in a circuit, the lower the current.

2.09 describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how to investigate this experimentally

in the bellow diagram the red box could represent a wire, a bulb, a resistor or a diode. 

By changing the resistance of the variable resistor the graphs are reproduced. 

2.22 identify common materials which are electrical conductors or insulators, including metals and plastics

Conducting Materials:

  • Copper
  • Aluminium
  • Gold
  • Silver

Will conduct electricity

Insulating Materials:

  • Glass
  • Air
  • Plastic
  • Rubber
  • Wood

Will not conduct electricity

2.23 practical: investigate how insulating materials can be charged by friction

  • Hold polythene rod and cloth next to up small pieces of paper one at a time, observe.
  • Now rub the rod with the cloth
  • Again hold close to small pieces of paper, observe.
  • Turn on a tap so a thin stream of water is flowing
  • Hold the rod about 1cm away from the water just below the nozzle, observe
  • Repeat with different material rods and cloths

3.01 use the following units: degree (°), hertz (Hz), metre (m), metre/second (m/s) and second (s)

the units for:

angle = degree (°) 

frequency = hertz (Hz)

wavelength = metre (m)

velocity = metre/second (m/s)

time = second (s) 

 

3.02 explain the difference between longitudinal and transverse waves

Transverse Waves:

  • A wave that vibrates or oscillates at right angles (perpendicular) to the direction in which energy is transferred/ the wave is moving.
  • g. Light

Longitudinal Waves:

  • A wave that vibrates or oscillates at parallel to (along) the direction in which energy is transferred/ the wave is moving.
  • g. Sound

3.03 know the definitions of amplitude, wavefront, frequency, wavelength and period of a wave

Key Definitions:

  • Wavefront: Created by overlapping lots of different waves. A wavefront is where all the vibrations are in phase and the same distance from the source.
  • Amplitude: The maximum displacement of particles from their equilibrium position.
  • Wavelength: The distance between a particular point on one cycle of the wave and the same point on the next cycle.
  • Frequency: The number of waves passing a particular point per second. Is measured in Hertz (Hz).
  • Time Period: The time it takes for one complete wave to pass a particular point.

3.04 know that waves transfer energy and information without transferring matter

Waves can transfer energy and information with out transferring matter, for example sun light, it transfers energy as it makes the earth warm without bringing any matter.  

3.08 explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer, and that this is known as the Doppler effect

Doppler Effect:

  • When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
  • If a car is moving, wavefronts of the sound are no longer evenly spaced.
    • Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
    • Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.

3.10 know that light is part of a continuous electromagnetic spectrum that includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space

Electromagnetic Spectrum:

  • A continuous spectrum of waves of differing frequency.
  • All electromagnetic waves have the following properties:
    • Transfer energy
    • Are transverse waves
    • Travel at the speed of light in a vacuum
    • Can be reflected and refracted

3.11 know the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum

Radio Waves

Microwaves

Infrared (IR)

Visible Light

Ultraviolet (UV)

X – Rays

Gamma Rays 

these are written in order of increasing frequency, lowest at the top

and decreasing wavelength, lowest at the bottom.

the colours displayed are in order of lowest frequency to the left highest frequency to the right.  

3.12 Explain some of the uses of electromagnetic radiations, including: radio waves: broadcasting and communications, microwaves: cooking and satellite transmissions, infrared: heaters and night vision equipment, visible light: optical fibres and photography, ultraviolet: fluorescent lamps, x-rays: observing the internal structure of objects and materials, including for medical applications, gamma rays: sterilising food and medical equipment.

uses of electromagnetic radiations, including:
• radio waves: broadcasting and communications
• microwaves: cooking and satellite transmissions
• infrared: heaters and night vision equipment
• visible light: optical fibres and photography
• ultraviolet: fluorescent lamps
• x-rays: observing the internal structure of objects and materials, including for medical applications
• gamma rays: sterilising food and medical equipment.

3.13 explain the detrimental effects of excessive exposure of the human body to electromagnetic waves, including: microwaves: internal heating of body tissue, infrared: skin burns, ultraviolet: damage to surface cells and blindness, gamma rays: cancer, mutation and describe simple protective measures against the risks

the detrimental effects of excessive exposure of the human body to electromagnetic waves:
• microwaves: internal heating of body tissue
• infrared: skin burns
• ultraviolet: damage to surface cells and blindness
• gamma rays: cancer, mutation

to reduce the risks:

  • wear sun glasses, sun cream and stay in shade for UV
  • Wear led clothing for Gamma 

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

1.       Set up your apparatus as shown in the diagram using a rectangular block.

2.       Shine the light ray through the glass block

3.       Use crosses to mark the path of the ray.

4.       Join up crosses with a ruler

5.       Draw on a normal where the ray enters the glass block

6.       Measure the angle of incidence and the angle of refraction and add these to your results table

7.       Comment on how the speed of the light has changed as the light moves between the mediums.

8.       Repeat this for different angles of incidence and different glass prisms. 

3.19 practical: investigate the refractive index of glass, using a glass block

1.       Set up your apparatus as shown in the diagram using a rectangular block.

2.       Shine the light ray through the glass block

3.       Use crosses to mark the path of the ray.

4.       Join up crosses with a ruler

5.       Draw on a normal where the ray enters the glass block

6.       Measure the angle of incidence and the angle of refraction and add these to your results table

7.       Calculate the refractive
index

8.       Repeat steps 2 – 7 using
a different angle of
incidence

9.       Find an average of your
results.

 

Select a set of flashcards to study:

     Terminology

     Skills and equipment

     Remove Flashcards

Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals

Go to Top