A wire carrying a DC current jumps up or down between the poles of a magnet depending on the directions of the current and magnetic field.
Force on a DC-current carrying wire in a magnetic field.
NCEA & Science Curriculum
Above: Jumping Wire 1. Below: Jumping wire 2
Download videos (right-click and “save as”):
Jumpingwire1.m4v (400 KB)
JumpingWire2.m4v (800 KB)
A long, flexible wire is best. Apply a large current briefly. Your power supply needs to tolerate short circuits, e.g. a car battery, current limited supply, or short-tolerant DC power supply such as the Unilab Electromagnetics power supply. If the DC is not smooth the wire will buzz at 50 Hz. Turn the magnet around to change the direction of the force. Change the direction of the current to change the direction of the force.
Make sure your power supply is current-limited or short-tolerant. A high voltage is not used in this demonstration but a current of several amps makes a better show.
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.
The force on a current-carrying wire in a magnetic field is the basis of a motor.
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