Falling chimney : When a tall chimney falls it sometimes breaks into two parts before it hits the ground. Investigate and explain this. Twisted rope : Hold a rope and twist one end of it. At some point the rope will form a helix or a loop. Investigate and explain the phenomenon. Loaded hoop : Fasten a small weight to the inside of a hoop and set the hoop in motion by giving it an initial push. Investigate the hoop’s motion. Water bombs : Some students are ineffective in water balloon fights as the balloons they throw rebound without bursting. Investigate the motion, deformation, and rebound of a balloon filled with fluid. Under what circumstances does the balloon burst? Electromagnetism Efficiency of a bicycle dynamo Efficiency of a DC motor A dynamo as a speedometer (conversion to accelerometer?) Efficiency of a transformer Saturation effects in a transformer Effect of air gaps in transformers or electromagnets Eddy current losses in transformers (solid core) Stray fields around transformers Variations in potential in a tank of conducting liquid The time taken for ions to recombine (e.g. blown down-wind of a flame) Torque-speed variations of a turntable motor An electroscope as a voltmeter The sensitivity of an electroscope as a charge measuring device The contraction of a spiral carrying a current The effect of thickness of metal on eddy current forces How high will a 'jumping ring' jump? (A ring over an iron core with a coil carrying a.c. on the core) The dependence of the speed of a DC motor on field current Change in length of a nickel rod in a magnetic field The design of an alternating current ammeter Does a flame conduct electricity? Does hot air conduct electricity?
What factors affect heating by eddy currents? How does the resistance between two points on a conducting sheet vary with distance? How does the resistance between two flat plates in a tank of conducting liquid vary with their spacing? Make an electrostatic dust collector How does the resistance in an LC circuit affect the resonance? Two magnets are arranged on top of each other such that one of them is fixed and the other one can move vertically. Investigate oscillations of the magnet. Charged plastic and paper fragments A charged plastic ruler can make a small piece of paper stand on its end. The separation of the ruler and the paper when the paper just stands up is a measure of the electrostatic force. Investigate the factors that affect the strength of this electrostatic force. Electromagnetic cannon A solenoid can be used to fire a small ball. A capacitor is used to energize the solenoid coil. Build a device with a capacitor charged to a maximum 50V. Investigate the relevant parameters and maximize the speed of the ball. Faraday Generator Construct a homopolar electric generator. Investigate the electrical properties of the device and find its efficiency. Coupled compasses Place a compass on a table. Place a similar compass next to the first one and shake it gently to make the needle start oscillating. The original compass' needle will start oscillating. Observe and explain the behaviour of these coupled oscillators. Transformers The "simple transformer law" relates output voltage to input voltage and turns ratio. Investigate the importance of frequency and other parameters in determining the non-ideal behaviour of transformers. Electromagnetic motor Attach a strong light magnet to the head of a steel screw. The screw can now hang from the terminal of a battery. Completing the circuit by a sliding contact on the magnet causes the screw to rotate. Investigate the parameters that determine the angular velocity of the screw. Rolling magnets