# Presentations

**Uncertainty Principle**

**What it shows:**

A pulse-modulated electromagnetic signal is simultaneously displayed in the time domain (on an oscilloscope) and in the frequency domain (on a spectrum analyzer). Using ∆n for the frequency spread (uncertainty in frequency) and ∆t for the duration of the pulse (uncertainty in the time domain), the frequency-time uncertainty relation is given by ^{1}

∆n ∆t ≥ ^{1}/_{4π}

Read more about Uncertainty Principle

**Faraday Induction**

**What it shows:**

The mathematical description of electromagnetic induction as formulated by Maxwell and Faraday requires two different sets of equations to calculate the induced voltage, depending on whether the coil is stationary and the magnet moving or vice versa. In fact, as this demonstration shows, the voltage is the same as predicted by the two sets of equations. Read more about Faraday Induction

**Liquid Crystal Sheets**

**What it shows:**

The selective reflection of a specific wavelength of light through a chiral nematic liquid crystal is temperature dependent and forms the basis for LCD thermograms and thermometers. Read more about Liquid Crystal Sheets

**Metals in Acid**

Curls of zinc and magnesium are dropped into 2M hydrochloric acid, and bubbles observer'd.

A 600ml beaker, clean and clear, is at the focal point of a camera projecting the image of 500 ml of 2M hydrochloric acid.

A curl of magnesium bubbles wildly, skittering across the surface of the acid.

A curl of zinc sinks to the bottom, and bubbles form at a steady rate.

**Mechanical Linear Amplifier**

**What it shows**:

One falling domino knocks down two, which in turn knock down three, etc. Use it to model cascade signaling.

**How it works**:

Twenty five rows of dominoes are set up in front of the first domino. Each successive row is comprised of one additional domino, e.g. the 2nd row has two, the 3rd row three, ... the 25th row has twenty five. A total of 325 dominoes get knocked down in a couple of seconds after the 1st one falls. Read more about Mechanical Linear Amplifier

**Newton's Cradle**

### What it shows:

Demonstration of elastic collisions between metal balls to show conservation of momentum and energy.

### How it works:

Newton's Cradle (less affectionately known as Newton's Balls) consists of six rigid balls hanging in a row with bifilar suspension. The balls hang so that they just barely touch their neighbor. Read more about Newton's Cradle

**Creep of Lead**

### What it shows:

A metal under stress will not fracture straight away, but will deform plastically due to the dislocation of crystal boundaries; this is called creep. Read more about Creep of Lead

**Vibrations on a Drumhead**

A driven membrane to show modes of vibration.

**Beats**

Two tuning forks with similar frequencies; one fork is variable in frequency to tune beating.

**What it shows:**

The interference of waves from two tuning forks of slightly differing frequencies gives rise to beating, that is, a modulated wave of frequency.

ν_{b} = (ν_{1} - ν_{2}) Read more about Beats