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State the two types of electrical charge.
Positive, negative
Describe what will happen when two opposite charges (e.g. a positive charge and negative charge) are brought close to each other.
They will attract
Describe what will happen when two like charges (e.g. two positive charges) are brought close to each other.
They will repel
Describe two experiments that demonstrate electrostatic charge.
Charged plastic rod picking up bits of paper/deflecting a gentle stream of water, rubbing a balloon on a jumper and making hair stand up/sticking the balloon to a wall, electric shocks, Van de Graaff generator, laser printers and photocopiers to get toner to stick to paper, even distribution of paint with spray guns
Define the term 'electric field'.
A region of space around a charge where another charge will experience a force.
Write down the rule regarding the direction of arrows when drawing electric field lines.
The arrows go out of a positive charge and into a negative charge/from positive to negative.
If electric field lines are close together, what does this indicate about the field's strength?
Strong electric field
If electric field lines are far apart, what does this indicate about the field's strength?
Weak electric field
Sketch the electric field pattern for a single positive charge.
Sketch the electric field pattern for a single negative charge.
Sketch the electric field pattern for two opposite charges (e.g. a positive charge and negative charge).
Sketch the electric field pattern for two positive charges.
Sketch the electric field pattern for two negative charges.
Sketch the electric field pattern for two oppositely charged parallel plates.
Describe what happens to a charged particle when it passes through a uniform electric field between two oppositely charged parallel plates.
It will experience a force and therefore deflect. Work is done on the charged particle to move it within the uniform field.
Sketch the path that an electron would take when moving through a uniform electric field between two oppositely charged parallel plates.
Sketch the path that a neutron would take when moving through a uniform electric field between two oppositely charged parallel plates.
Sketch the path that a proton would take when moving through a uniform electric field between two oppositely charged parallel plates.
If a positively charged particle is moved parallel to an electric field towards the positively charged plate, we say that the work done on it is equal to the change in _____________ ____________ _________.
Electrical potential energy
Write down the equation relating work done, electric charge and potential difference.
State the symbol and units for work done.
W, J
State the symbol and units for electric charge.
Q, C
State the symbol and units for potential difference.
V, V
Define the term 'voltage'.
The energy given to each coulomb of charge that passes through a power supply.
If a positively charged particle is released from the positively charged plate in a uniform electric field, we say that the work done on it is equal to the change in __________ _________.
Kinetic energy
Write down the equation relating kinetic energy, mass and speed.
State the symbol and units for kinetic energy.
Ek, J
State the symbol and units for mass.
m, kg
State the symbol and units for speed.
v, ms⁻¹
Write down the equation relating work done and change in kinetic energy.
State the symbol and units for change in kinetic energy.
ΔEk, J
Name the two poles on a magnet.
North, south
Describe what will happen when two opposite poles (e.g. a north pole and south pole) are brought close to each other.
They will attract
Describe what will happen when two like poles (e.g. two north poles) are brought close to each other.
They will repel
Describe what is meant by a 'magnetic field'.
A region of space around a magnet where another magnet will experience a force.
Write down the rule regarding the direction of arrows when drawing magnetic field lines.
The arrows go out of a north pole and into a south pole/from north to south.
If magnetic field lines are close together, what does this indicate about the field's strength?
Strong magnetic field
If magnetic field lines are far apart, what does this indicate about the field's strength?
Weak magnetic field
Sketch the magnetic field pattern for an isolated bar magnet.
If a current flows through a current-carrying wire, state what is produced around the wire.
A magnetic field
Describe the shape of the magnetic field produced around a current-carrying wire.
Circular
How can you determine the direction of the magnetic field around a current carrying wire?
Use the left hand grip rule. Point thumb in direction of current flow and grip wire. Fingers curl in the direction of the magnetic field.
A current-carrying wire will experience a _______ when placed in a magnetic field.
Force
True of False: a charged particle will experience a force as it moves through an external magnetic field.
TRUE
How can you determine the direction of the force on a charged particle moving in a magnetic field?
Use the right hand rule.
When using the right hand rule for a negative charge, what does the thumb represent?
Direction of motion/force
When using the right hand rule for a negative charge, what does the first/index finger represent?
Direction of magnetic field
When using the right hand rule for a negative charge, what does the second/middle finger represent?
Direction of current flow/charged particle
When using the right hand rule, what must you always do if dealing with a positively charged particle?
Reverse the direction of the force/motion
In terms of magnetic field direction when using the right hand rule, what does a dot inside a circle represent?
Out of the page
In terms of magnetic field direction when using the right hand rule, what does a cross represent?
Into the page
State the overall purpose of particle accelerators.
To accelerate charged particles, such as electrons or protons, to very high energies and speeds.
Explain how particle accelerators and detectors are used to produce and detect new particles.
Charged particles are accelerated to very high energies and speeds. These particles then collide with either a stationary target or other charged particles to produce even more particles and debris. Particle detectors are placed around the collision point to record and reveal the particles that emerge from the collision.
True or False: particle accelerators are used in the study of the nature of matter and fundamental particles.
TRUE
Particle accelerators can take different shapes. State two of these shapes.
Linear accelerators/cyclotrons (spiral)/synchrotrons (circular)
State two features that all particle accelerators have in common.
Electric field/electromagnets/vacuum chamber/source of particles/beam pipes
Describe how a cathode ray tube works as a particle accelerator.
Electrons are produced by the cathode when it is heated. A large potential difference is applied between two metal plates (anodes), creating an electric field between the plates. The electrons are accelerated between the anodes until they reach the deflection coils which change the path of the electron beam. When the electrons hit a phosphorescent screen, a tiny flash of light is produced.
Describe how a linear accelerator works as a particle accelerator.
A LINAC consists of hollow metal tubes placed in a vacuum. Charged particles are accelerated across the gaps between the tubes, but do not accelerate within the tubes.
Explain why a high frequency alternating supply is used in a linear accelerator.
An alternating supply continually changes the polarity of the tubes to ensure that the direction of the electric field is correct when a particle passes between the gaps/to ensure that the particle beam always accelerates in the same direction.
Explain why the lengths of the tubes increase along a linear accelerator.
As the speed of the particles increases, they travel further in the same time.
Describe how a cyclotron works as a particle accelerator.
A cyclotron consists of two D-shaped hollow metal structures called 'dees'. The protons are injected into the centre and are accelerated by the voltage between the dees.The protons move in a semicircular path due to the magnetic field round one dee until they cross the gap again and are accelerated by high voltage again. This time the polarity of voltage has been reversed to accelerate the protons in the opposite direction.As the protons travel faster, their radius around the dees increases until finally they are ejected as a high speed proton beam.
State what is used to change the direction of charged particles inside the 'dees' of a cyclotron.
Magnetic field
Explain why a high frequency alternating supply is used in a cyclotron.
For each successive crossing of the gap between the dees, the particles will need to accelerate in opposite directions each time. An alternating supply changes the polarity of the dees, which in turn changes the direction of the electric field across the gap.
Describe the shape of a synchrotron.
Like a linear accelerator that is bent into a ring.
In a synchrotron, why is a larger force eventually needed to keep the charged particles in a circular path as they gain speed?
When the particles reach relativisitic speeds, relativistic effects must be taken into account. This causes the mass of the particles to increase (known as relativistic mass) so a larger force is needed to steer them.
Describe how a synchrotron works as a particle accelerator.
Charged particles gain energy and speed as they travel around the ring-shaped accelerator. Electromagnets keep the particles travelling in a circular path. As the speed of the particles increases, the magnetic field strength must also be increased. If two beams of particles are colliding, they must be synchronised so that they accelerate in opposite directions at the same rate.
State the purpose of using electric fields in particle accelerators.
To accelerate the charged particles.
State the purpose of using magnetic fields in particle accelerators.
To change the direction of a beam of particles and keep them contained within the beam pipes.
State the name of the largest particle accelerator in the world.
Large Hadron Collider (LHC)
Explain how the Large Hadron Collider at CERN creates new particles to be studied.
Two beams of hadrons are accelerated in a circular ring in opposite directions and then collided head-on at very high energies. This creates new particles which can then be analysed using detectors.
Explain why the Large Hadron Collider at CERN requires the world's most powerful supercomputing centre.
To analyse the vast amounts of data created as a result of the collisions.
Explain why the Large Hadron Collider was created.
To answer some of the most fundamental questions in science including how the universe was created, what mass is and why some particles have no mass etc.
The size of objects can be compared using orders of magnitude. Describe what is meant by 'orders of magnitude'.
Powers of 10
A red blood cell is approximately 100 000 times larger in size than an atom. How many orders of magnitude is this?
5
Electrons are said to be 3 orders of magnitude smaller in size than protons and neutrons. What does this mean in terms of numbers?
Electrons are approximately 1000 times smaller in size than protons and neutrons.
