1. ELECTROMAGNETIC CANNON
Reporter: Hsieh, Tsung-Lin
Taiwan

2. Question
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.

3. Optimized Situation Ball I t 1. Magnitizing 2. Accelerating
3. At middle
4. Reverse current
5. Accelerating
6. Leaving

4. Relevant Parameters I(t) Ball Voltage (V) Solenoid Capacitance (C)
Length (l)
Layer
Radius (r) (→Inductance L)
Capacitance (C)
Resistance (R) (→frequency)‏
Ball
Magnetic susceptibility
Resistance
Mass (m)
Shape
Initial position (x0)
Typical energy transferring rate:

5. Experimental Setup
Power supply
Capacitor
Solinoid A B

6. Experimental Procedure
Charge the capacitor five times longer than its time constant.
Connect the capacitor to the solenoid.
Measure the distance the ball flies to estimate the initial speed.
Repeat the procedure
above.

7. Typical Result

8. Hypothesis The ball is magnetized.
Moves toward the less magnetic potential. S N
Magnetic domain model
Loop model
Constant current F x

9. How Fast It Moves Three time scales:
Magnetic field decay (RLC oscillation)
Magnitization time
Projectile passing through time

10. Simulation Assumptions
Particle.
Frictionless.
Circuit = RLC loop.
Path is along the axis of the solenoid. S

11. Simulation Formulationx

12. Voltage Speed is positively related to the voltage. C= 1470μF 5 layers
l= 1.5 cm
Position:
At the entry
m= g

13. Capacitance The optimized capacitance is 1470 μF. V= 50V 5 layers
l= 1.5 cm
Position:
At the entry
m= g

14. Numbers of Layers The optimized number is 5 layers. C= 1470μF V= 50V
l: 1.5 cm
Position:
At the entry
m: g

15. Position The optimized position is at the entry of the solenoid.
C= 1470μF
V= 50V
l: 1.5 cm
5 layers
m: g 5 4 3 2 1
Layer

16. Material
As a good ferromagnetic material, iron flies faster than any other ones.
C= 1470μF
V= 50V
l: 1.5 cm
5 layers
m: g Fe Co Ni Cu

17. Summary Magnetic force→fire the projectile
Low energy transferring rate.
Fastest speed: 31.4 m/s
V=50 V
C=1470 μF
Layers=5
Solenoid Length=1.5 cm
Position: At the entry
Ball mass=0.014g
Material: Iron
Complicated relationship.

18. Thank you!

19. Speed vs. Solenoid length
Parameter : Length (1, 1.5, 2, 2.5, 3 cm)‏
Initial Condition :
Voltage: 50 V
Capacitance: 1470 μF
Number of Layers: 5 cm
Position of Cannon: At the entry of the solenoid (0 mm)‏
Mass: g

20. Length
The optimized length is 1.5 cm.

21. Speed vs. Mass Parameter : Mass (0.014, 0.083, 0.19 g)‏
Initial Condition :
Voltage: 50 V
Capacitance: 1470 μF
Number of Layers: 5 cm
Length: 1.5 cm
Position of Cannon: At the entry of the solenoid (0 mm)‏

22. Mass
Faster when the projectile is lighter.

23. Sensitivity
Eliminate the data with significant deviation.