Tuning a Guitar using Resonance

There are many ways to tune a guitar. Many musicians would have tuned a string instrument using a tuning fork at some point. However, the conventional method of tuning with a tuning fork is by listening to beats while adjusting the tension of the string. The tuning fork is of a known frequency which corresponds

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Water Bender

A thin stream of water can be easily bent using a plastic comb or ruler which was previously rubbed with wool. This demonstrates the attractive forces between unlike charges.

Materials

  1. Plastic ruler
  2. Wool
  3. Water from a tap

Procedure

  1. Turn on the faucet for the thinnest stream of water with a consistent flow.
  2. Rub the plastic ruler with the wool.
  3. Place the part of the ruler which was rubbed near the stream of water without touching.

Science Explained

Water molecules are polar in nature, which means that one side (where the oxygen atoms are) is more negative while another side (where the hydrogen atom is) is more positive. When wool is rubbed with plastic, it deposits electrons on the ruler.

The electrons will remain on the plastic as it is a poor conductor of electricity. When placed near the stream of water, the water molecules reorientate themselves such that the positive pole of each molecule is now nearer to the ruler than the negative pole.

The resulting attractive forces are stronger than the repulsive forces as the forces between charges decrease when the distance apart increases.

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Electromagnet

Materials

  1. Insulated wire (about 1 m in length)
  2. Iron nail (at least 5 cm in length)
  3. 1.5 V battery
  4. Adhesive tape
  5. Small metal paper clip

Procedure

  1. Test that the iron nail is not already magnetised by trying to pick up the metal paper clip with it.
  2. Strip the two ends of the wire off its insulation. Leave about 1 cm bare on each end.
  3. Coil the wire around the iron nail, pushing each coil tightly together, to make a solenoid. Make sure you leave about 5 cm free at each end of the wire in order to connect the battery to the solenoid.
  4. If there is excess wire, make a second layer of coils around the first layer.
  5. Connect the ends of the wire to the terminals of the battery.
  6. Test the solenoid now by picking up the paper clip.
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Leyden Jar

A Leyden jar is a device used to store static electric charge. It can be used to conduct many experiments with electricity such as creating a spark across a gap. https://physicslens.com/leyden-jar/Follow

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Resonating Pendulums

The purpose of this demonstration is to teach the conditions and effects of resonance.  Our setup includes three sinkers hanging from a rod. I give credit to my colleague Alan Varella for showing me this demonstration when I first started teaching. What I do with my class is that I would jokingly announce that I

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Electroscope

An electroscope is a device that can be used to detect or measure the amount of charge in its vicinity. One of the earliest electroscopes is the gold-leaf electroscope which was invented by a British clergyman Abraham Bennet. This is a cheaper model of the leaf electroscope made using aluminum foil. Materials Paper clip Aluminum

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Oersted's Experiment

Hans Christian Oersted showed that an electric current can affect a compass needle in 1820. This confirms the direct relationship between electricity and magnetism, which in turn, paved the way for further understanding of the two. The direction of the magnetic field can be changed by flipping the wire around, which suggests that the direction

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04. Forces

Types of Forces Static friction Frictional force between surfaces at rest with respect to each other. It increases with increasing applied force up to a maximum value (which is proportional to normal contact force). Kinetic friction Frictional force acting between surfaces in relative motion. Viscous forces Resistive force experienced by a solid moving in a fluid.

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03. Dynamics

[accordions autoHeight='true'] [accordion title="1. Newton's Laws of Motion"] Newton's First Law:  a body will remain in its state of rest or uniform motion in a straight line unless acted upon by a resultant force. Newton's Second Law:  the rate of change of momentum of a body is proportional to the resultant force acting on it and the

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02. Kinematics

[accordions autoHeight='true'] [accordion title="1. Definitions"] Displacement is the distance travelled along a specified direction. Speed is the rate of change of distance travelled. Velocity is the rate of change of displacement. Acceleration is the rate of change of velocity. [/accordion] [accordion title="2. One-Dimensional Motion with Constant Acceleration"] s: displacement u: initial velocity v: final velocity a: acceleration t: time [/accordion]

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