HSC Physics Experiments

Experiment one: The Motor Effect


For the HSC Physics syllabus dot-points:

  • Perform a first-hand investigation to demonstrate the motor effect
  • Perform an investigation to model the generation of an electric current by moving a magnet in a coil or a coil near a magnet
  • Plan, choose equipment or resources for, and perform a first-hand investigation to predict and verify the effect on a generated electric current when: the distance between the coil and magnet is varied, the strength of the magnet is varied, the relative motion between the coil and the magnet is varied
  • Plan, choose equipment or resources for, and perform a first-hand investigation to demonstrate the production of an alternating current

For the first dot-point, we wound wires five times, threading each loop through the region between two strong permanent (neodymium) magnets. We then applied a current of 3 amps through the wire (our power supply was auto current-limiting so no excessive heat was produced). With 5 loops threaded, each with 3 amps, the total effective current was 3×5 = 15amps, and a movement of the wires were observed. The direction of force on the wire was as predicted by the right-hand push rule (aka right-hand palm rule).

For the second dot-point, we tested each condition (distance, strength and speed of magnet) on a coil connected to an ammeter and we observed a direct correlation between strength of magnet and induced current, a direct correlation between speed of magnet and induced current, and an inverse correlation between distance of magnet and induced current.

For the final dot-point, we moved a magnet in and out of a coil connected to an ammeter. The ammeter needle’s direction of movement continually reversed, indicating that an alternating current was produced. We also used a hand-wound AC generator to power an incandescent light bulb.

Experiment two: Transformers and Induction motors

For the HSC Physics ( http://www.duxcollege.com.au/ ) syllabus dot-points:

  • Perform an investigation to model the structure of a transformer to demonstrate how a secondary voltage is produced
  • Perform an investigation to demonstrate the principle of an AC induction motor

For the first dot-point, we constructed a model transformer using a 300 turn coil as the primary and a 600 turn coil as the secondary. Primary voltage was 18V AC and the secondary voltage was measured (by an AC-capable voltmeter) to be approx 35V AC when using laminated iron cores. The secondary voltage was observed to fall significantly (around 22V) when laminated iron core was replaced with a solid bar of iron (more eddy currents were possible with unlaminated iron core, decreasing efficiency of the magnetic flux transfer). We then switched the primary and secondary coil so that the primary was now 600 turns and the secondary was 300 turns. The secondary voltage was measured to be 8.5V AC. The percentage inefficiency was calculated to be the same in the step up and step down versions.

For the secondary dot-point, we constructed a single phase squirrel cage induction motor. Single phase induction motors generate initial torque due to the presence of shading coils. These coils delay the flux transfer at carefully chosen parts of the surrounding stator so that the initial change in flux produces a torque on the rotor. The squirrel cage core is not connected to any electricity — it moves only due to Lenz Law — it chases the external rotating magnetic field. We observed that the speed of the induction motor was at its highest if using a laminated core. When we changed the orientation of the rotor so that flux has to pass through a section of air, we observed the motor slow down significantly. When we bridged this gap with a solid iron bar, the rotor sped up slightly, but was still slower than its original speed. This again illustrates that air and iron bars are not as effective in transferring magnetic flux as laminated iron.

HSC Biology first-hand investigations coming soon!

HSC-First-hand investigations / experiments / practicals

In addition to learning the theoretical content of the course, students should remember not to neglect preparing for first-hand investigations and other practical skills-based dot-points that are in the HSC Chemistry or Physics syllabus. These dot-points can be examined in one or several of the following ways:

  1. Exam question asking for correct procedure, safety issues, sources of error, or other related discussion
  2. Practical exams

Practical exams are particularly important because all students will definitely have at least one in year 12, and they are often worth around 20% of total internal assessment. We recently filmed some of our in-class practical demonstrations of experiments that are most likely to come up in practical exams at school.

In addition to learning the theoretical content of the course, students should remember not to neglect preparing for first-hand investigations and other practical skills-based dot-points that are in the HSC Chemistry or Physics syllabus. These dot-points can be examined in one or several of the following ways:

Exam question asking for correct procedure, safety issues, sources of error, or other related discussion

Practical examsPractical exams are particularly important because all students will definitely have at least one in year 12, and they are often worth around 20% of total internal assessment. We recently filmed some of our in-class practical demonstrations of experiments that are most likely to come up in practical exams at school.

HSC Chemistry

Perform a first-hand investigation and solve problems using titrations including the preparation of standard solutions, and use available evidence to quantitatively and qualitatively describe the reaction between selected acids and bases

This experiment is important because it is one of the most commonly chosen experiments for Prac Exams. Prac Exams could come any time throughout year 12 — but most of the time they occur as part of your trial HSC exams, and usually worth around 20% of total internal assessment. Therefore it is important to pay close attention to proper titration procedure and understand the underlying processes of neutralization reactions.

For this titration, our unknown was a solution of NaOH (the analyte) and our standard solution was oxalic acid (crystals in dihydrate form) — the titrant. Glassware was rinsed properly with either deionised water or with the solution it was to contain (conical flask, volumetric flask — water / pipette, burette — solution). A total of 1 ‘rough titre’ and 3 accurate titres were done. The average of the 3 accurate titres were recorded and used to finally calculate the concentration of the unknown NaOH. Our indicator was phenolphthalein due to its slightly basic endpoint (the titration was between a strong base and a weak acid, therefore the equivalence point would be slightly basic). Tip: If required to make your own standard solution, make sure you design your standard solution so that it was enough moles for you to do 3 titres.


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