Physics Paper 2 Mistakes Flashcards
Explain what is meant by a capacitance of 120uF
Capacitor stores 120uC of charge for each volt of pd between the plates
What happens to capacitance if the dielectric is removed
Er decreases and capacitance decreases
What remains constant and what changes when the power supply remains connected (capacitance)
V constant
Q decreases
What remains constant and what changes when the power supply is disconnected (capacitance)
V increases
Q constant
Explain what is meant by ionisation
When an atom loses an electron
Discuss the energy transfers that take place in the accelerator as the ion passes through it
Potential energy of the ion is transferred to KE of ion.
Power supply transfers energy to the ion.
Decrease in energy stored in supply = increase in KE stored by ion
Discuss how the path changes when an ion enters the velocity selector with a velocity greater than v
The electric force is constant.
F = BQv and since B and Q are constant, F is directly proportional to v
When velocity increases, the magnetic force acting on the ion increases.
Ion accelerates in the direction of the force (state the direction of force using Flemings rules)
Ions created in the ioniser may have the same charge but a different number of nucleons.
Discuss how the path of an ion in the mass separator is affected when it has more nucleons
Bqv = mv^2 / r
r = mv / Bq
v, B, q are constant to r is directly proportional to m and so r increases
An alpha particle is targeted towards a gold nucleus with 79 protons.
The target nucleus is changed to one with fewer protons. The alpha particle is given the same initial KE.
Explain any changes that occur to the distance r.
R gets smaller.
Less force so needs to travel further to lose same initial KE.
Define gravitational potential at a point
Work done per unit mass in moving an object from infinity to a point
Explain why gravitational potential is always negative
Gravitational potential is defined as 0 at infinity.
(Forces are attractive) so work must be done on the mass to reach infinity therefore it is negative.
Describe and explain 2 features of a geostationary orbit
Time period of 24 hours.
In the plane of the equator.
Always above the same location on Earth
Explain the purpose of the core in the transformer
Core focuses/directs the magnetic field round to the secondary coil
Describe and explain 2 features of the core that improve the efficiency of the transformer
Made from soft iron so easily magnetised/demagnetised
The core is laminated to reduce eddy currents
Explain why transformers only work continuously when supplied with an alternating current
So there is a constant change in flux in the core
