Magnetism, Nuclei & Options
PH5.1 CAPACITANCE
Content
- The parallel plate capacitor.
- Concept of capacitance.
- Factors affecting capacitance.
- Energy stored in a capacitor.
- Capacitors in series and parallel.
- Capacitor discharge.
AMPLIFICATION OF CONTENT Candidates should be able to:
5.1 (a) understand that a simple parallel plate capacitor consists of a pair of equal parallel metal plates separated by vacuum or air,
5.1 (b) understand that the capacitor stores energy by transferring charge from one plate to the other, so that the plates carry equal but opposite charges (the net charge being zero),
5.1 (c) define capacitance as C=Q/V,
5.1 (d) use C=εoA/d for a parallel plate capacitor, with no dielectric,
5.1 (e) know that a dielectric increases the capacitance of a vacuum-spaced capacitor;
5.1 (f) recall that the E field within a parallel plate capacitor is uniform and of value V/d,
5.1 (g) use the equation U=1/2QV for the energy stored in a capacitor,
5.1 (h) use formulae for capacitors in series and in parallel,
5.1 (i) understand the process by which a capacitor discharges through a resistor,
5.1 (j) use the equation Q=Q0e−t/RC where RC is the time constant.
PH5.2 B-FIELDS
Content
- Concept of magnetic fields (B-fields).
- Force on a current-carrying conductor.
- Force on a moving charge.
- Magnetic fields due to currents.
- Effect of a ferrous core.
- Force between current – carrying conductors.
- Definition of the ampere.
- Measurement of magnetic field strength B.
- Deflection of beams of charged particles in electric and magnetic fields.
AMPLIFICATION OF CONTENT Candidates should be able to:
5.2 (a) predict the direction of the force on a current-carrying conductor in a magnetic field,
5.2 (b)]] define magnetic field B by considering the force on a currentcarrying conductor in a magnetic field; recall and use F = BIl sin θ ,
5.2 (c) use F = Bqv sinθ for a moving charge in a magnetic field;
5.2 (e) understand the processes involved in the production of a Hall voltage and understand that VH ∝ B for constant I.
5.2 (f) describe how to investigate steady magnetic fields with a Hall probe,
5.2 (g) sketch the magnetic fields due to a current in
(i) a long straight wire,
(ii) a long solenoid,
5.2 (h) use the equations B=μ0I/2πa and B=μ0nI for the field strengths due to a long straight wire and in a long solenoid,
5.2 (i) know that adding an iron core increases the field strength in a solenoid,
5.2 (j) explain why current-carrying conductors exert a force on each other and predict the directions of the forces,
5.2 (k) understand how the equation for the force between two currents in straight wires leads to the definition of the ampere,
5.2 (m) describe quantitatively how ion beams, i.e. charged particles, are deflected in uniform electric and magnetic fields,
5.2 (o) apply knowledge of the motion of charged particles in magnetic and electric fields to linear accelerators, cyclotrons and synchrotrons.
