Summary of Nuclear Physics

Nuclear Physics Summary

Quantum Physics Summary

Quantum Physics Summary

Current Balance Demonstration/Experiment

Photo above showing the wire frame where current will pass through. The frame is completely between the poles of the u-shaped magnet (North is red) during experiment.

Photo above shows that the wire frame is not in contact with the magnet. 

The video of the experiment is embedded below or http://youtu.be/nkS7wCCzGiY. You may pause the video at each current reading to obtain the following data. The balance is zeroed to measure ony the gain/loss in mass of magnet.

Questions: What is the direction of the force on the wire frame and the magnet? Why is the magnet getting "heavier"? When the current is reversed (http://youtu.be/hnU4g4NBXXo), why is the magnet getting "lighter"?

The electronic balance gives reading in grammes. The magnetic force is obtained by multiplying the balance reading by 10 N/kg (or 9.8 N/kg if you want to be accurate). Since

F = BIL

Plot a graph of magnetic force F against current I in the wire frame. If a linear trend is obtained, the gradient will be BL where L is measured to be 4.0 cm. 

Gradient = 4.466 mN/A = 0.004466 N/A

Therefore B = 0.004466/0.040 = 0.11 T

This value is reasonable because the magnetic flux density of the magnet should be much greater than Earth's intrinsic magnetic field (~10 nT) and flux density of more than 1 T is hard to obtain in common school lab.

Demonstrations and questions on electrons in electric or magnetic field

Demo 1 - Increasing deflection plates potential difference

Questions:

• What do you notice about the electron beam when the deflection plates p.d. is increased?
• Explain your answer to the previous question.

Demo 2 - Increasing accelerating potential  

Questions:

• What do you notice about the electron beam when the accelerating p.d. is increased?
• Explain your answer to the previous question.

Demo 3 - Electron beam in uniform magnetic field while accelerating potential is increased

Questions:

• What do you notice about the electron beam in uniform when the accelerating potential is increased?
• Explain your answer to the previous question.

Demo 4 - Electron in increasing magnetic field

Questions:

• What do you notice about the electron beam in uniform field when magnetic flux density is increased?
• Explain your answer to the previous question.

Demo 5 - Electrons enter the magnetic field not at right angle (Helical motion)

Questions:

• What do you notice about the electron enter the magnetic field not at right angle?
• Explain your answer to the previous question. The video below may help you.

Wheels are everywhere

This is something that should be related to your experience when shopping with your family at supermarkets, etc. Observe the behaviour of the wheels and provide your responses to the questions after the video.

Collision carts simulation for practical on 3/4/13

Please complete the lab assignment P06 by 5/4/13.

The simulation can be downloaded here.

Special thanks for Wee Loo Kang for creating and refining this simulation with and for River Valley High School.

What happens when you drop a spring balance with the measured object still on it?

This video (shot at 120 frame-per-second) can be used to show that the spring balance does not measure the weight/gravitational force of the object hanging below rather it is measuring the force exerted by object.

Concepts:

• The spring extends because the object exerts a force on the spring balance and the spring balance exerts an equal force on the object (Newton's 3rd Law). The force on the object exerted by the spring balance is equal to the gravitational force on the object when the system is in equilibrium (either at rest or at constant velocity). 
• When the system is accelerated (or free fall in this video), the force exerted on the spring balance by the object is different (zero at free fall) while the gravitational force on the object remains constant

Performance of Understanding on Kinematics and Dynamics (15/3/2013)

Stumble upon this through the Modelling Physics community in USA.

Using Direct Measurement Videos 

"Direct Measurement videos show situations that students can use to learn and apply physics concepts. Grids, rulers, and frame-counters are added as overlays on the video. These allow students to make precise measurements of quantities such as position and time, without needing additional video analysis software."  - http://serc.carleton.edu/sp/library/direct_measurement_video/index.html

Resources

• Worksheet
• Videos used in the worksheet - video 1, video 2, video 3 and video 4