4.11 know and use the relationship between work done, force and distance moved in the direction of the force: W = F × d
Work Done (J) = Force (N) x distance moved (m)
4.12 know that work done is equal to energy transferred
|
Work done = energy transferred |
4.13 know and use the relationship between gravitational potential energy, mass, gravitational field strength and height: GPE = m × g × h
Gravitational potential energy (J) = Mass (kg) x gravitational field strength (N/kg) x height (m)
4.14 know and use the relationship: kinetic energy = 1/2×m×v^2
Kinetic energy (J) = 0.5 x mass (kg) x velocity (m/s) 2
4.15 understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work
Because energy is conserved the decrease in GPE = increase in KE, for a falling object if no energy is lost to the surroundings
4.16 describe power as the rate of transfer of energy or the rate of doing work
power is the rate of transfer of energy, or the rate of work done. so p = E/t
5.01 use the following units: degree Celsius (°C), Kelvin (K), joule (J), kilogram (kg), kilogram/metre3 (kg/m3), metre (m), metre2 (m2), metre3 (m3), metre/second (m/s), metre/second2 (m/s2), newton (N) and pascal (Pa)
The units for:
temperature: degree Celsius (°C) or Kelvin (K)
Energy: Joule (J)
mass: Kilogram (kg)
density: kilogram/metre cubed (kg/m3)
distance: metre (m)
area: metre squared (m2)
volume: metre cubed (m3)
velocity: metre per second (m/s)
acceleration: metre per second squared (m/s2)
force: newton (N)
pressure: pascal (Pa)
5.02 use the following unit: joules/kilogram degree Celsius (J/kg °C)
the unit for
specific heat capacity: joules/kilogram degree Celsius (J/kg °C)
5.03 know and use the relationship between density, mass and volume:
Units of density depend on units used for mass and volume:
E.g. mass in [g] and volume in [cm3] gives density in [g/cm3], however mass in [kg] and volume in [m3] gives density in [kg/m3].
5.04 practical: investigate density using direct measurements of mass and volume
- The density of an object can be found by measuring the mass and volume and applying the formula above to calculate the density.
- For a regular object use a ruler to measure the lengths needed to determine the volume.
- For an irregular object submerge it in water and measure the displaced volume.
- Measure the mass of either type of object using a measuring balance.
5.05 know and use the relationship between pressure, force and area:
pressure (Pa) = force (N)/ area (m2)
- Pressure is defined as force per unit area.
- One pascal (Pa) is equivalent to one N/m2
5.06 understand how the pressure at a point in a gas or liquid at rest acts equally in all directions
Pressure in liquids:
Pressure in liquids acts equally in all directions as long as the liquid is not moving.
5.07 know and use the relationship for pressure difference: p = h × ρ × g
Pressure difference [Pa] = Density [kg/m3] x g [N/kg] x Height [m]
ΔP = ρ g h
- The equation can be used in liquids or gases provided you know their densities.
P1 – Patm = ρ g h
P1 = ρ g h + Patm
5.10 describe the arrangement and motion of particles in solids, liquids and gases
solids:
- Tightly packed
- Held in fixed pattern
- Vibrate about fixed positions
liquids:
- Tightly packed
- Can slide over each other
gasses:
- Very spread out
- Move with rapid, random motion
5.11 practical: obtain a temperature–time graph to show the constant temperature during a change of state
- Remove the boiling tube of stearic acid from
the water bath - Place the tube into a beaker of room
temperature water - Add a separate thermometer to the water
- Take readings from the thermometer in the
stearic acid and the water every minute
[Make sure to avoid parallax error while doing so] - Note readings in the table below
- Note on the table when you observe the stearic
acid change from a liquid to a solid. - Plot your results in a graph
5.12 know that specific heat capacity is the energy required to change the temperature of an object by one degree Celsius per kilogram of mass (J/kg °C)
Specific heat capacity:
- Amount of heat energy required to increase the temperature of 1kg of a substance by 10
- Unit J/kg 0C
5.13 use the equation: change in thermal energy: ΔQ = m × c × ΔT
Change in thermal energy [J] = Mass [kg] x Specific heat capacity [J/kg 0C] x Change in temperature [0C]
5.14 practical: investigate the specific heat capacity of materials including water and some solids
- Set up the apparatus as shown the diagram.
- Make note of all measurements: current (A), potential difference (V), mass (kg).
- Use the electronic balance to measure the mass of your
- Record the initial temperature of you block.
- Switch on the heater and start your stopwatch.
[You will now leave the heater on for 10 minutes] - While the heater is switched on take readings from the
Ammeter and the Voltmeter. - Use these to calculate the Thermal Energy that will be
supplied to the block in 10 minutes - Record the temperature of your block after 10 minutes.
- Calculate the Change in Temperature
5.15 explain how molecules in a gas have random motion and that they exert a force and hence a pressure on the walls of a container
Gas laws:
- Gas molecules have rapid and random motion.
- When they hit the walls of the container, they exert a force.
- Pressure = Force/Area
5.16 understand why there is an absolute zero of temperature which is –273 °C
Absolute zero:
- At absolute zero the particles have no thermal energy or kinetic energy, so they cannot exert a force.
- Absolute zero = 0 Kelvin = -2730C
5.17 describe the Kelvin scale of temperature and be able to convert between the Kelvin and Celsius scales
0 K = -273 0C
E.g. 100K = -1730C
2000C = 473K
5.18 understand why an increase in temperature results in an increase in the average speed of gas molecules
As you increase the temperature of a gas, the kinetic energy of the gas particles increases and thus their average speed also increases.
5.19 know that the Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules
The Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules.
5.20 Explain, for a fixed amount of gas, the qualitative relationship between: pressure and volume at constant temperature, pressure and Kelvin temperature at constant volume.
- As you heat the gas, the kinetic energy of the particles increases, and thus so does their average speed.
- This means more collisions per second with the walls, and they exert a larger force on the wall.
- This causes in the total pressure being exerted by the particles to rise.
- If temperature is constant, the average speed of the particles is constant.
- If the same number of particles is placed in a container of smaller volume they will hit the walls of the container more often.
- More collisions per second means that the particles are exerting a larger force on the wall over the same time, so average force exerted on the walls has increased.
5.21 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume:
P1/T1 = P2/T2
*Temperature must be in Kelvin
Temperature law:
For a fixed mass of gas at constant volume, the pressure is directly proportional to the Kelvin temperature
5.22 use the relationship between the pressure and volume of a fixed mass of gas at constant temperature:
P1V1 = P2V2
Boyle’s law:
For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume.
6.01 use the following units: ampere (A), volt (V) and watt (W)
The unit for:
Current : amps (A)
Potential Difference : volt (V)
power : watt (W)
6.02 know that magnets repel and attract other magnets and attract magnetic substances
Opposites attract: North attracts South and South attracts North
Like charges repel: Two Norths will repel each other
6.03 describe the properties of magnetically hard and soft materials
Permanent magnets are made of magnetically hard materials such as steel. These materials retain their magnetism once magnetised.
Some materials like iron are magnetically soft. They lose their magnetism once they are no longer exposed to a magnetic field. They are used as temporary magnets such as electromagnets.
6.04 understand the term magnetic field line
Around every magnet there is a region of space where we can detect magnetism (where magnetic materials will be affected).
This is called the magnetic field and in a diagram we represent this with magnetic field lines.
The magnetic field lines should always point from north to south.
6.05 know that magnetism is induced in some materials when they are placed in a magnetic field
|
When magnetic materials are bought near or touch the pole of a strong or permanent magnet, they become magnets. This magnetic character is induced in the objects and it is removed when the permanent magnet is removed. This is a temporary magnet Magnetism is induced in the paperclips so each paperclip can attract another one |
6.06 practical: investigate the magnetic field pattern for a permanent bar magnet and between two bar magnets
- Place your bar magnet in the centre of the next page and draw around it.
- Place a compass at one pole of the bar magnet.
- Draw a ‘dot’ to show there the compass is pointing,
- Move the compass so the opposite end of the needle is pointing to the dot,
- Repeat steps 3 and 4 until to reach the other pole of the magnet.
- Do this procedure at least 5 times from different points on the pole of the magnet.
*Tip, try to be as accurate as possible when drawing your dots* - Join up your dots to create the field line plots
6.07 describe how to use two permanent magnets to produce a uniform magnetic field pattern
|
A uniform magnetic field is comprised of straight, parallel lines which are evenly spaced. Between two opposite charges on flat magnets, a uniform magnetic field is formed. |
6.08 know that an electric current in a conductor produces a magnetic field around it
|
A current travelling along a wire produces a circular magnetic field around the wire. The magnetic field direction can be determined using the right hand grip rule. |
6.09 describe the construction of electromagnets
A soft iron core wrapped in wire. When current flows through the coil of wire it becomes magnetic.
6.11 know that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field
|
The movement of the charged particle is a current so it produces a magnetic field. This magnetic field interacts with the permanent magnetic field to create a force. The force is perpendicular to the direction of motion and the permanent magnetic field. |
6.12 understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers
Motor
- Current flows in the wire/coil.
- This creates a magnetic field around the wire/coil.
- This magnetic field interacts with the field from the permanent magnet.
- This produces a force on the wire/coil which moves the wire/coil.
- The split-ring commutator changes the direction of the current every half turn as it spins. This reverses the direction of the forces, allowing the coil to continue spinning.
Loudspeaker
- An alternating current from the source passes though the coils in the speaker.
- This current is constantly changing direction and magnitude
- This current creates a magnetic field around the coil
- This field interacts with the magnetic field from the permanent magnets
- Creating a constantly changing force on the coil.
- This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
- The cone causes vibrations which we hear as sound waves.
6.13 use the left-hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
|
Fleming’s left hand rule. Thumb: force First finger: Magnetic Field Second finger: Current |
6.14 describe how the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current
|
If you increase the magnitude of the current through a wire or the size of the magnet being used, you increase the force on the wire. If you change the direction of the current or reverse the poles of the magnet, you change the direction of the force on the wire |
6.15 know that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors that affect the size of the induced voltage
When a conductor (can be a wire, coil or just a piece of metal) experiences a changing magnetic field a potential difference or voltage is induced in it. The strength of the potential difference depends on the strength of the magnetic field, how fast it changes i.e. how fast the coil is spinning, and how much of the conductor is exposed to the field i.e. how many turns in the coil.
6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field, and describe the factors that affect the size of the induced voltage
|
Electricity can be generated by either moving a magnet inside a coil of wire or rotating a coil inside a permanent magnetic field.
Model answer for a generator (Rotating coil): · Coil is rotated within a magnetic field · As it turns the coil cuts the magnetic field lines. · This induces a voltage (or current) in the coil. · This can then be connected to an existing circuit. · In a generator, energy is being converted from kinetic (mechanical) energy into electrical energy. · The size of the induced voltage (or current) can be increased by: · Using a stronger magnet · Having more turns in the coil · Spinning/moving the coil faster.
Model answer for a generator (Rotating magnet) · Magnet is rotated within a coil · As it turns the coil cuts the constantly changing magnetic field lines from the magnet. · This induces a voltage (or current) in the coil. · This can then be connected to an existing circuit. · In a generator, energy is being converted from kinetic (mechanical) energy into electrical energy. · The size of the induced voltage (or current) can be increased by: · Using a stronger magnet · Having more turns in the coil · Spinning/moving the magnet faster.
|
6.17 describe the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides
|
AC current in the primary coil produces a changing magnetic field around the primary coil. The iron core channels the changing field through the secondary coil. The changing magnetic field induces a voltage in the secondary coil. |
6.18 explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy
|
Step Up transformers increase the voltage – more secondary turns than primary Step Down transformers decrease the voltage – more primary turns than secondary |
