1.30 know and use the relationship between the moment of a force and its perpendicular distance from the pivot
moment = force x perpendicular distance from the pivot
1.32 use the principle of moments for a simple system of parallel forces acting in one plane
The principle of moments states that when the clockwise moments are equal to the anticlockwise moments a body will be in equilibrium.
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.
2.01 use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W)
unit for:
current : Ampere (A)
charge : coulomb (C)
resistance : ohm (Ω)
time : second (s)
potential difference : volt (V)
power : watt (W)
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
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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.
2.05 use the relationship between energy transferred, current, voltage and time: E= I × V × T
Energy (J) = potential difference (V) x current (A) x Time (s)
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.
2.10 describe the qualitative effect of changing resistance on the current in a circuit
Since V = IR, as you increase the resistance in a circuit, the current will decrease.
2.11 describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature
LDR
As illumination increases, resistance decreases
Thermistor
As temperature increases, resistance decreases.
2.12 know that lamps and LEDs can be used to indicate the presence of a current in a circuit
A lamp can be added to a circuit to check for a current. If current is flowing, the lamp will light up.
2.13 know and use the relationship between voltage, current and resistance: V = I × R
Potential difference (V) = Current (A) x Resistance (Ω)
2.14 know that current is the rate of flow of charge
current is rate of flow of charge so I=Q/t
2.15 know and use the relationship between charge, current and time: Q = I × t
Charge (C) = Current (A) x Time (s)
2.16 know that electric current in solid metallic conductors is a flow of negatively charged electrons
Electrons are negatively charged and free to flow in a metal so carry charge
2.17 understand why current is conserved at a junction in a circuit
At a junction current ‘splits’ to take both paths.
It comes back together when the paths meet again.
I1 = I2 + I3 +I4
2.19 calculate the currents, voltages and resistances of two resistive components connected in a series circuit
VT = V1 + V2
IT = I1 = I2
RT = R1 + R2
2.21 know and use the relationship between energy transferred, charge and voltage: E = Q × V
Energy Transferred (J) = charge (C) x Voltage (V)
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
2.28 explain some uses of electrostatic charges, e.g. in photocopiers and inkjet printers
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Paper is charged negatively in certain regions. Then positively charged paint droplets are sprayed onto the paper and attracted to the negative regions of the paper giving the desired image. |
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.
3.05 know and use the relationship between the speed, frequency and wavelength of a wave: v = f × λ
wave speed (m/s) = frequency (Hz) x Wavelength (m)
3.06 use the relationship between frequency and time period: time period x frequency = 1 or f = 1/T
Frequency (Hz) = 1/ Time Period (s)
3.07 use the above relationships in different contexts including sound waves and electromagnetic waves
You will need to use any of the in 3.05 and 3.06 to solve problems to do with sound waves and electromagnetic (light) waves
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.
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uses of electromagnetic radiations, including: |
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
3.14 know that light waves are transverse waves and that they can be reflected and refracted
light is a transverse wave that can be reflected and refracted
3.17 practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms
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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. |
