7.08 understand how to balance nuclear equations in terms of mass and charge
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Particle |
Symbol |
Mass |
Charge |
|
Alpha |
α |
4 |
+2 |
|
Beta |
β |
0 |
-1 |
|
Gamma |
γ |
0 |
0 |
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 |
7.06 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. |
7.04 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).
7.03 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 |
7.02 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
7.01 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)
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 |
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. |
6.16 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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6.15 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.
6.14 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 |
6.13 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 |
6.12 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.
6.11 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
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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. |
6.09 describe the construction of electromagnets
A soft iron core wrapped in wire. When current flows through the coil of wire it becomes magnetic.
6.08 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. |
6.07 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. |
6.05 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 |
6.04 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.
6.03 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.
6.02 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
6.01 use the following units: ampere (A), volt (V) and watt (W)
The unit for:
Current : amps (A)
Potential Difference : volt (V)
power : watt (W)
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.
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
5.20 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.
5.19 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.
5.18 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.
5.17 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
5.16 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
5.15 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
5.13 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]
5.12 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
5.10 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
5.07 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
5.05 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
5.04 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.
5.03 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].
5.02 use the following unit: joules/kilogram degree Celsius (J/kg °C)
the unit for
specific heat capacity: joules/kilogram degree Celsius (J/kg °C)
5.01 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)
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
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
4.14 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