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
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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
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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
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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
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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
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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.
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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
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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
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Step Up transformers increase the voltage – more secondary turns than primary Step Down transformers decrease the voltage – more primary turns than secondary |
7.01 use the following units: becquerel (Bq), centimetre (cm), hour (h), minute (min) and second (s)
the units for:
frequency of decay : becquerel (Bq), 1 (Bq) for 1 decay / sec
distance : centimetres (cm), normally however is (m)
time : hour (h), minute (min) but normally (s)
7.02 describe the structure of an atom in terms of protons, neutrons and electrons and use symbols such as 146C to describe particular nuclei
Atoms are made up of protons, neutrons and electrons.
Protons and neutrons are in the nucleus, electrons are in the shells
7.03 know the terms atomic (proton) number, mass (nucleon) number and isotope
|
Atomic (proton) number is the number of protons in the nucleus of an atom. Mass (nucleon) number is the total number of protons and neutrons in the nucleus of an atom. An isotope is an atom of the same element, i.e. it has the same number of protons/same atomic number, but has a different number of neutrons/different mass number. Two atoms with the same atomic number but different mass numbers are isotopes see 7.02 for example |
7.04 know that alpha (α) particles, beta (β−) particles, and gamma (γ) rays are ionising radiations emitted from unstable nuclei in a random process
There are three types of ionising radiation:
Alpha (α), Beta (β) and Gamma (γ)
One radioactive source can release different types of radiation.
Ionisation is when an atom loses or gains an electron, causing it to become an ion (an atom which is positively or negatively charged).
7.06 practical: investigate the penetration powers of different types of radiation using either radioactive sources or simulations
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Detect using a Geiger Müller Tube. Try the three different materials in order, paper then aluminium then lead. Count rate will significantly decrease if radiation is stopped. |
7.07 describe the effects on the atomic and mass numbers of a nucleus of the emission of each of the four main types of radiation (alpha, beta, gamma and neutron radiation)
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Alpha decay: · 2 protons and 2 neutrons are lost. · Mass number decreases by 4 · Atomic number decreases by 2 Beta decay · 1 neutron is converted to an electron (lost from the atom) and proton · Mass number is unchanged · Atomic number increases by 1 Gamma decay · Energy is lost from an atom in the form of an electromagnetic wave · Mass number is unchanged · Atomic number is unchanged |
7.08 understand how to balance nuclear equations in terms of mass and charge
|
Particle |
Symbol |
Mass |
Charge |
|
Alpha |
α |
4 |
+2 |
|
Beta |
β |
0 |
-1 |
|
Gamma |
γ |
0 |
0 |
7.09 know that photographic film or a Geiger−Müller detector can detect ionising radiations
Geiger Müller detector:
When connected to a counter, the detector will be able to measure radioactivity.
Photographic film:
Radiation will cause photographic film to darken.
7.10 explain the sources of background (ionising) radiation from Earth and space
- radon in air
- Granit in rocks
- Cosmic rays
- Medical equipment
- Food and drink
7.11 know that the activity of a radioactive source decreases over a period of time and is measured in becquerels
The activity of a radioactive source decreases over a period of time and is
measured in becquerels.
7.12 know the definition of the term half-life and understand that it is different for different radioactive isotopes
The Half-life is the time taken for the radioactivity of a specific isotope to fall to half its original value.
7.13 use the concept of the half-life to carry out simple calculations on activity, including graphical methods
Numerical:
A radioactive source has a half-life of 2 hours. If the mass starts at 40mg, what will the mass be after 4 hours?
Graphical:
Several different times for the half-life can be calculated and averaged.
7.14 describe uses of radioactivity in industry and medicine
Gamma radiography:
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Medical tracer: – Radioactive tracer put in body (swallowed/injected) – Detector put around body – Computer generates an image |
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Gauging: – Coal absorbs a lot of radiation – If only a small amount of radiation is detected back after it is reflected by what you are trying to gauge, lots of coal is present. |
Radiotherapy
- High doses of radiation are directed at cancer cells
- Cancer cells are killed
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Pipe tracers: – A radioactive material which emits gamma radiation with a short half-life is put in the water – A detector is placed above the pipe – A spike in detected radioactivity suggests a leak in the pipe |
Sterilisation:
- Medical equipment irradiated
- Kills all living matter on tools (e.g. bacteria)
Carbon dating:
7.15 describe the difference between contamination and irradiation
- Contamination:
Occurs when material that contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired.
- Irradiation:
The process by which an object is exposed to radiation.
7.17 know that nuclear reactions, including fission, fusion and radioactive decay, can be a source of energy
- Nuclear Fission:
The process where heavy atoms are split into smaller, lighter atoms. This releases energy.
- Nuclear Fission:
The process where lighter atoms are forced to join together to make heavier atoms. This releases energy.
- Radioactive Decay:
Within the core of the Earth, radioactive isotopes of elements such as uranium, thorium and potassium provide a large proportion of the heat within the Earth through radioactive decay.
7.19 know that the fission of U-235 produces two radioactive daughter nuclei and a small number of neutrons
- A slow moving neutron is absorbed by a uranium 235 nucleus.
- The resulting uranium 236 nucleus is unstable.
- It splits to form two smaller daughter nuclei, three neutrons and gamma radiation.
7.20 describe how a chain reaction can be set up if the neutrons produced by one fission strike other U-235 nuclei
Chain Reaction:
- The three neutrons produced by the fission may hit other nuclei of uranium 235, causing the process to repeat.
- For a chain reaction to occur, there is a minimum mass of uranium 235 required. This is known as the critical mass.
